阅读说明：本技术 具有大流体有效表面的mems (MEMS with large fluid active surface ) 是由 塞尔久·兰加 霍尔格·康拉德 贝尔特·凯泽 于 2020-03-17 设计创作，主要内容包括：本发明涉及一MEMS包括包含一空腔的一基材。该MEMS包括一可移动层布置结构,该可移动层布置结构布置在该空腔中,该空腔包含一第一桁条、一第二桁条及布置在该第一桁条与该第二桁条之间并固定在与之电气绝缘的分立区域处的一第三桁条。该可移动层布置结构被组配用以响应于一第一桁条与一第三桁条之间的一电位、或响应于该第二桁条与该第三桁条之间的一电位而在一基材平面中沿着一移动方向进行一移动。第一、第二及第三桁条是该可移动层布置结构的一第一层的部分。该可移动层布置结构包含沿着垂直于该基材平面的一方向相邻于该第一层布置的一第二层。该第二层沿着该移动方向采可移动方式布置。(The invention relates to a MEMS comprising a substrate comprising a cavity. The MEMS includes a movable layer arrangement disposed in the cavity, the cavity including a first beam, a second beam, and a third beam disposed between the first beam and the second beam and secured at discrete areas electrically isolated therefrom. The movable layer arrangement is configured to perform a movement in a movement direction in a substrate plane in response to an electrical potential between a first beam and a third beam, or in response to an electrical potential between the second beam and the third beam. The first, second and third beams are part of a first layer of the movable layer arrangement. The movable layer arrangement includes a second layer arranged adjacent to the first layer along a direction perpendicular to the substrate plane. The second layer is movably arranged along the direction of movement.)

1. A MEMS, comprising:

a substrate (12) including a cavity (16);

a movable layer arrangement (36) arranged in the cavity (16), the cavity comprising a first stringer (26a), a second stringer (26b) and a third stringer (26c) arranged between the first stringer (26a) and the second stringer (26b) and fixed at discrete regions electrically insulated therefrom;

wherein the movable layer arrangement (36) is configured to perform a movement along a movement direction (34) in a substrate plane in response to an electrical potential between the first beam (26a) and the third beam (26c), or in response to an electrical potential between the second beam (26b) and the third beam (26 c);

wherein the first, second and third stringers (26a-c) are a first layer (24; 24) of the movable layer arrangement (36)₁) And the movable layer arrangement comprises a layer adjacent to the first layer (24; 24₁) A second layer (24) of arrangement₂(ii) a 18) Wherein the second layer (24)₂(ii) a 18) Is arranged movably along the direction of movement (34).

2. MEMS according to claim 1, wherein the stringers (26a-c) are electrostatic, piezoelectric, thermo-mechanical electrodes.

3. MEMS according to claim 1 or 2, wherein the second layer (24)₂) Structured into a fourth stringer (26d), a fifth stringer-a strip (26e) and a sixth stringer (26f), wherein the fourth stringer (26d) is arranged adjacent to the first stringer (26 a); and the fifth stringer (26e) is adjacent to the second stringer (26 b); and the sixth stringer (26f) is adjacent to the third stringer (26c) along the direction (z) perpendicular to the substrate plane.

4. The MEMS of claim 3, wherein the stringers of adjacent layers are offset from one another.

5. MEMS according to claim 3 or 4, wherein at least one of the first (26a) and fourth (26d), second (26b) and fifth (26e), and third (26c) and sixth (26f) stringers is arranged in the first layer (24)₁) And the second layer (24)₂) An intermediate layer (22) therebetween₂) Are mechanically connected to each other.

6. MEMS according to any of claims 3 to 5, wherein the third stringer (26c) and the sixth stringer (26f) are arranged via an arrangement in the first layer (24)₁) And the second layer (24)₂) An intermediate layer (22) therebetween₂) Are mechanically connected with each other; and removing the intermediate layer between the first stringer (26a) and the fourth stringer (26d), on the one hand, and between the second stringer (26b) and the fifth stringer (26e), on the other hand, so as to separate the first stringer (26a) from the fourth stringer (26d) and the second stringer (26b) from the fifth stringer (26 e).

7. MEMS according to any of claims 3 to 5, wherein the first (26a) and fourth (26d) stringers on the one hand and the second (26b) and fifth (26e) stringers on the other hand are arranged via an arrangement in the first layer (24)₁) And the second layer (24)₂) An intermediate layer (22) therebetween₂) Are mechanically connected with each other; and removing the intermediate layer (22) between the third stringer (26c) and the sixth stringer (26f)₂) So as to provide a gap between the third stringer and the sixth stringer.

8. MEMS according to claim 3, wherein the first layer (24)₁) And the second layer (24)₂) Via an intermediate layer (22)₂) Are connected to each other in a region of the substrate (12); wherein the intermediate layer (22) is removed in a region of the cavity (16) between the first stringer (26a) and the fourth stringer (26d), between the second stringer (26b) and the fifth stringer (26e), and between the third stringer (26c) and the sixth stringer (26f)₂)。

9. MEMS according to claim 8, wherein the first, second and third beams (26a-c) form a first movable element (32) of the movable layer structure (36)₁) And wherein the fourth, fifth and sixth beams (26d-f) form a second movable element (32) of the movable layer structure (36)₂) Wherein the first movable element (32)₁) Relative to the second movable element (32)₂) Is arranged movably along the direction of movement (34).

10. The MEMS of claim 9, wherein

Different potentials can be applied between the first stringer (26a) and the third stringer (26c) on the one hand and between the fourth stringer (26d) and the sixth stringer (26f) on the other hand, and/or

Wherein different electrical potentials can be applied between the second stringer (26b) and the third stringer (26c) on the one hand and between the fifth stringer (26e) and the sixth stringer (26f) on the other hand.

11. MEMS according to claim 1 or 2, wherein the first, second and third stringers (26a,26b, 26c) form a movable element (32), and wherein the second layer (18) forms a resistor structure (48) for interacting with a fluid in the cavity (16), mechanically connected to the movable element (32), and moving and/or deforming together with the movable element (32).

12. The MEMS as recited in claim 11, wherein the resistor structure (48) is connected to the first layer by an intermediate layer (22).

13. MEMS according to claim 11 or 12, wherein the first layer (24)₁) Further comprising a piggyback element (62) mechanically fixed to the first or second stringer (26a,26b) on a side facing away from the third stringer (26c), wherein the resistor structure (48) is at least partially arranged on the piggyback element (62).

14. MEMS according to claim 13, wherein the piggyback element (62) is firmly mechanically connected to the first or second stringer (26a,26b) via a coupling element (64), wherein the coupling element (64) is arranged in a region which experiences the maximum deflection during a deformation of the movable element (32).

15. MEMS according to any of claims 11 to 14, wherein the resistor structure (48) comprises a number of partial elements (48a-j) arranged perpendicular to the direction of movement (34) and parallel to the substrate plane along an axial extension direction (y) of the movable layer arrangement structure (36).

16. MEMS according to claim 15, wherein the partial elements (48a-j) have a distance (72) from each other along the axial extension direction (y).

17. MEMS according to claim 16, wherein the distance (72) is at most 100 μm, preferably at most 100 μm, particularly preferably at most 1 μm.

18. MEMS according to any of claims 15 to 17, wherein some elements (48a-j) are firmly mechanically connected to the first stringer (26a) or to the second stringer (26b) or to the third stringer (26 c).

19. MEMS according to any of claims 15 to 17, wherein partial elements (48a-j) are arranged on at least two of the first stringer (26a), the second stringer (26b) and the third stringer (26 c).

20. MEMS according to any of claims 11 to 19, wherein a first distance (58) between the resistor structure (48) and the substrate (12) along or opposite the moving direction (34)₁) Greater than a second distance (42) between the first stringer (26a) and the third stringer (26c)₁)。

21. The MEMS as recited in claim 20, wherein the first distance (58)₁) Is greater than the second distance (42)₁) By a factor in the range of at least 1 to 20, preferably 3 to 10, particularly preferably 5 to 7.

22. MEMS according to any of claims 11 to 21, wherein the second layer (18) has a layer thickness (56) perpendicular to the substrate plane, the layer thickness (56) being larger than the first layer (24)₁) By a factor in the range of at least 1 to 20, preferably 3 to 10, particularly preferably 5 to 7.

23. MEMS according to any of claims 11 to 22, wherein for the first layer (24)₁) And a distance (42) between the first stringer (26a) and the third stringer (26c)₁) The first layer (24)₁) An aspect ratio of less than 40.

24. MEMS according to any of claims 11 to 23, wherein the resistor structure (48) is arranged at the first layer (24)₁) Further comprises a first resistor structure arranged on a first side of the first layer (24)₁) A second resistor structure on a second side of the substrate, the second side being disposed opposite the first side.

25. MEMS according to any of claims 11-24, wherein the resistor structure (48) provides a liquid resistance for a fluid arranged in the cavity (16).

26. MEMS according to any of claims 11 to 25, wherein the movable layer arrangement (36) comprises a third layer (24) structured into a fourth beam (26d), a fifth beam (26e) and a sixth beam (26f)₂) (ii) a Wherein the first, second and third beams (26a-c) form a first movable element (32)₁) And wherein the fourth, fifth and sixth beams (26d-f) form a second movable element (32) of the movable layer arrangement (36)₂)。

27. MEMS according to claim 26, wherein the first movable element (32)₁) Is mechanically connected or not connected to the second movable element (32)₂)。

28. MEMS according to claim 26 or 27, wherein the resistor structure (48) is a first resistor structure (48)₁) And comprises a second movable element (32) connected to the second movable element₂) A second resistor structure (48)₂)。

29. MEMS according to claim 28, wherein the first movable element (32)₁) And the second movable element (32)₂) Are arranged adjacent to each other and at the first resistor structure (48)₁) And the second resistor structure (48)₂) Arranged along a direction (z) perpendicular to the plane of the substrate.

30. The MEMS as recited in claim 28, wherein the first resistor structure (48)₁) And the second resistor structure (48)₂) Are arranged adjacent to each other and at the first movable element (32)₁) And the second movable element (32)₂) Arranged along a direction (z) perpendicular to the plane of the substrate.

31. The MEMS as recited in claim 30, wherein the first resistor structure (48)₁) And the second resistorStructure (48)₂) Are movable relative to each other.

32. MEMS according to any of the preceding claims, wherein the movable layer structure (36) comprises a flex beam structure clamped on one side at the substrate (12).

33. MEMS according to any of the preceding claims, wherein the first layer (24; 24)₁) And the second layer (24)₂(ii) a 18) A layer perpendicular to the plane of the substrate has a thickness of at least 50 μm.

34. MEMS according to any of the preceding claims, wherein an axial extension of the movable layer arrangement along a direction (y) parallel to the substrate plane and perpendicular to the moving direction (36) has a dimension of at least a factor of 0.5 compared to a dimension of the movable layer arrangement along a thickness direction and has a value in the range of 10 μ ι η to 5000 μ ι η, preferably 100 μ ι η to 2000 μ ι η, particularly preferred 400 μ ι η to 1500 μ ι η.

35. MEMS according to any of the preceding claims, wherein the cavity (16) is fluidically connected to an external environment (88) of the substrate (12) via at least one opening (28), wherein the at least one opening (28) is arranged in a plane of the movable layer arrangement.

36. MEMS according to any of the preceding claims, configured as a MEMS pump or as a MEMS speaker, as a MEMS microphone or as a MEMS THz waveguide.

37. MEMS according to any of the preceding claims, comprising control means (86) configured to control the movable layer structure.

38. A MEMS according to claim 37, wherein the first, second and third beams (26a-c) form a first movable element (32)₁) And the MEMS comprises a plurality of movable elements, wherein the control means (86) is configured to individually control the plurality of movable elements.

Technical Field

The present invention relates to micro-electro-mechanical systems (MEMS) configured to include a large effective area for interaction with a fluid. In particular, the present invention relates to NED (nanoscopic electrostatic actuation) with enlarged lateral surfaces due to the stacking and/or arrangement of the back structures or resistor structures.

Background

The principle of NED (nanoscopic electrostatic actuation) is described in WO2012/095185A 1. NED is a novel MEMS (micro-electro-mechanical systems) actuator principle. From a technical point of view, NED actuators are basically of two types: vertical NED (V-NED) and lateral NED (L-NED). In V-NED, an object such as silicon (Si stringer) is moved vertically, i.e., out of the plane of the substrate, such as defined by a Si disk or wafer. In L-NED, an object such as a Si stringer is moved laterally, i.e., in-plane, such as within a Si disk.

In the NED gap, the situation can be described as the smaller the electrode gap, the greater the applied electromotive force and thus the greater the desired deflection of the stringer. This means that it is almost always desirable that the gap distance is very small (e.g. in the nanometer range).

Technically, such small distances between the electrodes are not always easy to produce. Typically, when producing a gap in silicon, the method used is deep silicon etching (DSi). One widely used DSi process is the so-called Bosch process. With the Bosch process, very small gap distances can be etched, but only when the aspect ratio, i.e. the quotient between the depth and the width of a trench, is not much larger than 30.

This means that the Bosch process can only etch to a depth of up to 10 μm with reasonable quality when a gap distance of 300nm is required. For many L-NED applications, a depth of only 10 μm is not sufficient. When a depth of, for example, 100 μm is required, this may result in that the width of the trench must also be made ten times as large, i.e. about 3 μm wide.

FIG. 11a shows a schematic cross-sectional view or cross-section of a known MEMS 1000 configured as an L-NED. The MEMS 1000 may include a substrate layer 1002, such as a handle wafer of a BSOI (bonded silicon on insulator) wafer. A device layer of the BSOI wafer is stacked thereon, with layers 1002 and 1004 being connected through an oxide layer, i.e., through a Buried Oxide (BOX) of the BSIO wafer. The outer electrodes 1008a and 1008b, which are composed of the layer 1004, are arranged such that an inner electrode 1008c of the layer 1004 is arranged between the outer electrodes 1008a and 1008b, wherein the NED gaps 10121 and 10122 are arranged between the electrodes, which can be obtained, for example, by means of the DSi method. Outer trenches 1014 between outer electrodes 1008a and 10008b, respectively₁And 1014₂And layer 1004 leaving material as an outer substrate may define movable beams formed by the electrodes and may also be formed by DSi, for example. A height 1016 of the L-NED actuator, for example, may be related to the extension of the movable element, possibly by adding a gap between the electrodes 1008a, 1008b and/or 1008c and the layer 1002, and perpendicular to a substrate plane defined, for example, by a main extension direction of the layer 1002.

FIG. 11b shows a schematic top view of MEMS 1000. Electrodes 1008a and 1008c and 1008b and 1008c may each be securely mechanically connected to each other via an insulating layer 1022 disposed over discrete regions. The movable element formed by movable electrodes 1008a, 1008b, and 1008c is movable along a lateral movement direction 1024 arranged in a plane.

Lateral movement of the L-NED actuator may cause movement of a medium (e.g., air or liquid) in which the actuator moves. This movement of the medium can be used to produce a (micro) speaker or a (micro) pump based on an L-NED actuator. The volume of a loudspeaker or the power of a pump depends on the size of the volume (air or liquid) that is moved. Illustrated as an L-NED actuator, the volume moved is determined by the amount of deflection, i.e., by the magnitude along the direction of movement 1024 and the height 1016 of the L-NED actuator. Accordingly, it is desirable to produce MEMS speakers and/or MEMS pumps that are high in L-NED actuators and that have a large deflection.

As noted above, the following general statements apply to L-NED actuators:

the smaller the L-NED actuator gap, the greater the deflection;

the smaller the gap between the L-NED actuators, the smaller the height of the actuators during production (Bosch process) based on the limited aspect ratio.

This means that the production process makes it difficult to combine a small clearance (large deflection) with a large height of the stringer.

The principle of a micro-speaker or micro-pump based on L-NED is described in DE 102015210919A 1.

Fig. 12 shows a schematic cross-sectional view of a MEMS2000 known therefrom, largely corresponding to the side cross-sectional view of the MEMS 1000, wherein the layer 1002 may additionally comprise an opening 1026 for allowing a volume flow between a cavity 1028 within which the electrodes 1008a, 1008b and 1008c move and an external environment of the MEMS 2000. In addition, by means of another insulating layer 1006₂A further substrate layer 1032 is arranged which may form, for example, a lid of the MEMS2000 and also includes an opening 1034 which may, for example, serve as an inlet opening for the cavity 1028 when the opening 1026 serves as an acoustic or fluid outlet. Distance 1036 between layer 1002 and electrodes 1008a, 1008b, and/or 1008c₁And/or a distance 1036 between the electrodes and the lid wafer 1032₂And may generally have a value of about 1 μm (determined by thermal oxidation of Si: 10nm to 10 μm).

The principal principle according to fig. 12 is to provide an L-NED actuator produced on a BSOI wafer, also described as device wafer in the context of fig. 11a and 11b, and having a lid wafer 1032. The device wafer and the lid wafer may be bonded by a bonding method. The inlet and outlet 1026 and 1034 are provided for acoustic signals or fluids.

The L-NED stringer is laterally movable so that an acoustic or pump effect may be created. When the ratio of the L-NED height to the L-NED gap is large, the acoustic and pump effects become more effective, the larger the better. The ratio of the L-NED height 1016 to the L-NED gap 1012 is approximately 30. This limitation is due to the production process of Si technology.

In addition, the L-NED stringer according to fig. 12 is limited by the vertical pull-in effect (mechanical and/or electrical contact between the pull-in L-NED stringer and the lid or handle wafer, such as contact by electrostatic forces). This means that when a voltage is applied to one of the L-NED electrodes 1008a, 1008b, or 1008c and the layers 1002 and/or 1032 are connected to ground, an electrical vertical force is created which pulls the L-NED beam either bottom or top. Since the distances 10361 and 10362 between the L-NED stringers and the lid wafer 1032 or handle wafer 1002 are small (in the range of 1bis 2 μm), movement of the L-NED stringers towards the bottom (vertical, z-direction) may result in a pull-in effect. Vertical pull-in is undesirable for two reasons:

mechanical properties: mechanical contact between the L-NED stringers and the lid or handle wafers during operation can lead to mechanical failure of the device. In addition, the intended very high motion fidelity (desired systematic connection between input and output signals) can be limited, resulting in distortion, friction losses and non-linearity;

electrical: electrical contact between the L-NED stringers and the lid or handle wafers during operation can lead to electrical destruction (shorting) of the device.

DE 102017203722 a1 shows that a large aspect ratio can be achieved by subsequently displacing the electrodes relative to each other. The subsequent displacement of the electrodes is a further process which is difficult to control and therefore error-prone.

Accordingly, MEMS with in-plane movable elements having a large aspect ratio and which are easy to produce would be desirable.

Disclosure of Invention

Accordingly, it is an object of the present invention to provide a MEMS having a large aspect ratio and being easy to produce.

The object is solved by the subject matter of the independent claims.

One core idea of the present invention is to find that the electrode layer of the L-NED device can be supplemented by yet another second layer providing additional areas for interaction with the fluid. The second layer can be produced by means of an existing and controllable process, so that a simple production can be achieved and at the same time the effective aspect ratio is increased.

According to one embodiment, a MEMS includes a substrate including a cavity. The MEMS includes a movable layer arrangement disposed in the cavity, the cavity including a first beam, a second beam, and a third beam disposed between the first beam and the second beam and secured at discrete areas electrically isolated therefrom, wherein the movable layer arrangement is configured to undergo a movement in a direction of movement in a substrate plane according to an electrical potential between the first beam and the third beam, or in response to an electrical potential between the second beam and the third beam. The first, second and third beams are portions of a first layer of the movable layer arrangement. The movable layer arrangement structure includes a second layer arranged adjacent to the first layer along a direction perpendicular to the substrate plane and movably arranged along the moving direction. The second layer enables the additional active area to interact with a fluid, i.e. a gas and/or a liquid, compared to the stringer arrangement.

According to one embodiment, the second layer is structured into a fourth, fifth and sixth beam. Along a direction perpendicular to the substrate plane, such as z, at least in a rest state of the MEMS, the fourth stringer is disposed adjacent to the first stringer, the fifth stringer is disposed adjacent to the second stringer, and the sixth stringer is disposed adjacent to the third stringer. This enables additional actively controllable areas.

According to an embodiment, the first stringer is mechanically connected to the fourth beam, and/or the second stringer is mechanically connected to the fifth beam, and/or the third stringer is mechanically connected to the sixth stringer via an intermediate layer arranged between the first layer and the second layer. This enables small fluid losses between the beams and a mechanical coupling of the movements of the individual beams.

According to an embodiment, the third beam and the sixth beam are mechanically connected to each other via an intermediate layer arranged between the first layer and the second layer. Removing the intermediate layer between the first and fourth stringers on the one hand and the second and fifth stringers on the other hand, so as to space the first and fourth stringers and the second and fifth stringers. This results in a low mass being able to move, since the moving coupling can still be achieved via mechanical fixings between the fourth, fifth and sixth stringers.

According to an embodiment, the first and fourth stringers on the one hand and the second and fifth stringers on the other hand are mechanically connected to each other via an intermediate layer arranged between the first and second layers. Removing the intermediate layer between the third stringer and the sixth stringer to provide a gap between the third stringer and the sixth stringer. This also achieves low quality.

According to one embodiment, the first layer and the second layer are connected to each other in a region of the substrate via an intermediate layer, such as an insulating layer, such as silicon oxide, silicon nitride or a polymer. Removing the intermediate layer in a region between the first and fourth stringers, between the second and fifth stringers, and between the third and sixth stringers of the cavity. This enables the first, second and third beams to move independently of the fourth, fifth and sixth beams.

According to one embodiment, the first, second and third beams form a first movable element of the movable layer structure. The fourth, fifth and sixth beams form a second movable element of the movable layer structure. The first movable element is movably arranged relative to the second movable element along the moving direction. This enables individual deflection of the movable element, providing a high degree of freedom in both sensing and actuation.

According to an embodiment, a different electrical potential may be applied between the first and third stringers on the one hand and the fourth and sixth stringers on the other hand. Alternatively or additionally, a different electrical potential may be applied between the second and third stringers on the one hand and the fifth and sixth stringers on the other hand. This enables the movable elements to be evaluated and/or controlled independently, e.g. out of phase or phase shifted.

Some of the above embodiments are described such that the second layer is structured as stringers and the effective area is enlarged by additional stringer area compared to the first layer. Further embodiments of features that may alternatively or additionally be combined with an inventive device relate to the fact that the second layer provides a resistor structure for interaction with a fluid in the cavity. For this purpose, it is sufficient to configure the resistor structure in an electrically passive manner, which achieves simple implementation. At the same time, the pull-in effect between the resistor structure and the outer region may be reduced or prevented.

According to an embodiment, the first, second and third beams form a movable element. The second layer forms a resistor structure for interacting with a fluid in the cavity. The resistor structure is mechanically connected to the movable element and is moved together by the movable element. This enables the actual effective aspect ratio to be enlarged by an additional arrangement of the resistor structure, wherein this can be implemented by means of a simple and accurate procedure.

According to one embodiment, the resistor structure is connected to the first layer by means of an intermediate layer. This enables a simple configuration to be achieved by forming the MEMS from a stacked structure.

According to one embodiment, the first layer comprises, in addition to the first, second and third stringers, a piggyback element which is mechanically fastened to the first or second stringer on a side facing away from the third stringer, i.e. in the plane of the outside of the stringer arrangement. The resistor structure is at least partially arranged on the piggyback element. This renders it possible to arrange the resistor structure on an element which is not necessarily actively electrically deformed, so that a low deformation energy is required to deform the resistor structure.

According to one embodiment, the piggyback element is mechanically fixed to the first, second or third stringer. The resistor structure is at least partially arranged on the piggyback element. This enables a simple production.

According to one embodiment, the piggyback element is mechanically connected to the first or second beam via a coupling element, wherein the coupling element is arranged in a region which is at most slightly deformed during deformation of the active element in a region of maximum deflection of the movable element, and the movable element is not arranged at a high material strain. This results in the prevention of unnecessarily high mechanical energy for deformation of the coupling element and/or the resistor structure.

According to one embodiment, the resistor structure comprises a number of partial elements arranged perpendicular to the direction of movement and parallel to the substrate plane along an axial extension of the movable layer arrangement. This results in a reduction of the effective stiffness of the resistor structure, so that low forces are sufficient to influence the deformation of the resistor structure. Alternatively or additionally, this renders it possible to reduce or prevent mechanical interactions between the individual partial elements.

According to one embodiment, the partial elements are spaced apart from one another in a projection into a plane perpendicular to the substrate plane and perpendicular to the direction of movement. This enables freedom of contact during deformation and/or a small mass of the resistor structure.

According to one embodiment, the distance is at most 100 μm, preferably at most 10 μm, and particularly preferably at most 2 μm. Like a wall-like structure, this achieves low fluid loss or fluid effect of the resistor structure.

According to one embodiment, the partial elements are alternatively firmly mechanically connected to the first stringer or to the second stringer or to the third stringer. This achieves low fluid loss by reducing or preventing a diagonal from moving the fluid point.

According to an embodiment, the partial elements are arranged on at least two of the first, second and third stringers. Although the wall elements effective in the direction of movement can be damped by the partial elements arranged offset with respect to the direction of depth, the resistor structure achieves a completely or partially symmetrical mass distribution at the stringer. Possible adverse effects can be compensated for by an overlap of the partial areas projected into a projection in the plane perpendicular to the substrate plane.

According to an embodiment, a first distance between the resistor structure and the substrate is larger than a second distance between the first beam and the third beam along or opposite to the moving direction. Since the resistor structure can be assembled in a passive manner and implemented for fluid interaction, the arrangement of the gap structure limited by the aspect ratio can be omitted. Thus, in summary, larger gaps are possible, so that a large effective dimension in the z-direction can be achieved without complicated processing, which is beneficial.

According to one embodiment, the first distance is greater than the second distance by a factor in the range of at least 1 to 20, preferably 3 to 10, particularly preferably 5 to 7.

According to one embodiment, the second layer comprises a layer cap perpendicular to the substrate plane, such as along z, which is larger than the first layer by a factor in the range of at least 1 to 20, preferably 3 to 10, particularly preferably 5 to 7. This enables a particularly efficient MEMS.

According to one embodiment, an aspect ratio of the first layer is less than 40 for a layer thickness of the first layer and a distance between the first and third beams or the second and third beams, which enables simple process control.

According to an embodiment, the resistor structure is a first resistor structure arranged on a first side of the first layer. Further, the MEMS includes a second resistor structure disposed on a second side of the first layer, the second side being disposed opposite the first side. This achieves a particularly high efficiency of the MEMS by expanding the effective area of the fluid on both sides.

According to an embodiment, the resistor structure provides a liquid resistance for a fluid arranged in the cavity, which is particularly advantageous for actuator implementations like loudspeakers or pumps, but also for sensing implementations like microphones or other implementations like MEMS THz waveguides.

According to one embodiment, the advantages of the resistor structure and additional beam layers may be combined. To this end, the movable layer arrangement comprises a third layer structured into fourth, fifth and sixth beams, such that two beam layers and at least one resistor structure are implemented, which leads to a further increase in efficiency.

Here, the first, second and third beams may be mechanically connected to form a first movable element, while the fourth, fifth and sixth beams may be mechanically connected to form a second movable element.

According to an embodiment, the first movable element is mechanically connected to the second movable element, which achieves a higher aspect ratio when considering the technical limitations of aspect ratios and a lower operating voltage since high forces can already be generated by low voltages.

According to an embodiment, the resistor structure is a first resistor structure, wherein the MEMS comprises a second resistor structure connected to the second movable element. On the one hand, this allows a high flexibility by individual control and/or sensing or detection by means of one of the different movable elements whose effective area is enlarged on both sides, and a simple production.

According to an embodiment, the first movable element and the second movable element are arranged adjacent to each other along a direction perpendicular to the substrate plane and between the first resistor structure and the second resistor structure. This enables the arrangement of a possible passive resistor structure outside the structure that may be connected to ground, so that low attractive forces and pull-in effects may be prevented.

According to an alternative embodiment, the first resistor structure and the second resistor structure are arranged adjacent to each other and between the first movable element and the second movable element along a direction perpendicular to the substrate plane. This enables a large distance between the movable elements and thus a low electrical cross-over effect.

According to an embodiment, the first resistor structure and the second resistor structure are movable relative to each other, which is advantageous for controlling the movable elements independently of each other, in particular in actuator implementation aspects.

According to one embodiment, the movable layer structure comprises a flexure beam structure clamped on one side of the substrate. A flexing stringer structure clamped on one side achieves a large deflection at the free end, which is particularly advantageous since, according to the above embodiments, the pull-in effect is reduced or prevented, for which prevention a clamping can be provided on both sides, where the reduction in amplitude can be prevented.

According to one embodiment, a layer thickness of the first layer and the second layer perpendicular to the substrate plane is at least 50 μm. This enables a very large MEMS.

According to an embodiment, an axial extension of the movable layer arrangement parallel to the substrate plane and perpendicular to the moving direction is configured such that a dimension of at least a factor of 0.5 is obtained for the height of the moving structure, which is particularly advantageous, since the dimension or length affects the efficiency in the same way as the height or thickness.

According to one embodiment, the cavity is fluidly connected to the environment outside the substrate through at least one opening, wherein the at least one opening is arranged in a plane of the movable layer arrangement. This enables the use of the bottom layer and/or the cover layer for other purposes, since the chip area can be used for other purposes than an opening.

According to an embodiment, the MEMS is configured as a MEMS pump, as a MEMS speaker, as a MEMS microphone or as a MEMS THz waveguide.

According to one embodiment, the MEMS comprises control means configured to control the movable layer structure.

According to one embodiment, the first, second and third beams form a first movable element, wherein the MEMS comprises a plurality of movable elements, i.e. at least two movable elements. The control means is configured to individually control a plurality of movable elements, which realizes a high degree of freedom in implementing the MEMS.

Further advantageous configurations are subject matter of further dependent claims.

Drawings

Preferred embodiments of the present invention will be discussed below with reference to the accompanying drawings. It shows that:

FIG. 1 is a schematic cross-sectional view of a MEMS in accordance with an embodiment;

FIG. 2 is a schematic cross-sectional view of a MEMS in accordance with one embodiment, where additional actuator thickness is taken through additional electrodes;

FIG. 3a is a schematic cross-sectional view of a MEMS in accordance with an embodiment in which the outer electrodes of a first layer and a second layer are connected to each other via an intermediate layer, while in the inner electrodes the intermediate layer is completely removed or not disposed;

FIG. 3b is a schematic cross-sectional view of a MEMS according to an embodiment in which the intermediate layer is disposed between the inner electrodes to mechanically connect the two electrodes firmly to each other, but is removed between the outer portions, as compared to the MEMS of FIG. 3 a;

FIG. 4a is a schematic cross-sectional view of a MEMS in accordance with an embodiment in which the second layer of the movable layer arrangement comprises a resistor structure, e.g., composed of a substrate layer;

FIG. 4b is a schematic cross-sectional view of the MEMS of FIG. 4a, wherein the resistor structure is securely mechanically connected to an external electrode;

FIG. 4c is a schematic cross-sectional view of a MEMS in accordance with one embodiment, wherein the movable element includes a piggyback element in a plane of the electrodes of the first layer, the resistor structure being firmly mechanically connected thereto via a coupling element;

FIG. 4d is a schematic top view of a MEMS in accordance with yet another embodiment, wherein the coupling element is disposed on a freely deflectable end of the movable element clamped on one side of the substrate;

FIG. 4e is a schematic cross-sectional view of the MEMS of FIG. 4d in a cross-sectional plane A' A of FIG. 4 d;

FIG. 5a is a schematic view of a MEMS in accordance with one embodiment in which the movable element is clamped securely to two sides;

FIG. 5b is a schematic view of the MEMS of FIG. 5a in a deflected state of the movable element;

FIG. 6a is a schematic top view of a MEMS in accordance with one embodiment, wherein a portion of the elements of the resistor structure are disposed on one of the electrodes;

FIG. 6b is a schematic top view of a MEMS in accordance with an embodiment in which some elements of the resistor structure are disposed on at least two of the electrodes;

FIG. 7a is a schematic cross-sectional view of a MEMS, such as the MEMS of FIG. 4a, through a cap layer in accordance with an embodiment;

FIG. 7b is a schematic cross-sectional view of a MEMS in accordance with an embodiment in which an opening for connecting the cavity to an external environment is disposed outside the substrate in a plane of the movable layer arrangement;

FIG. 8a is a schematic cross-sectional view of a MEMS combining features of a dual set of electrodes and a back structure or resistor structure in accordance with an embodiment;

FIG. 8b is a schematic cross-sectional view of a MEMS in accordance with an embodiment in which the relative orientation of two movable elements with respect to the MEMS of FIG. 8a is swapped such that the resistor structures are disposed adjacent to one another;

FIG. 9 is a schematic cross-sectional view of a MEMS in accordance with an embodiment in which electrodes of different layers are connected to each other and have an offset;

FIG. 10 is a schematic cross-sectional view of a MEMS in accordance with an embodiment in which the electrodes of different layers are not in contact with each other and have an offset;

FIG. 11a is a schematic cross-sectional view or section of a known MEMS configured as an L-NED;

FIG. 11b is a schematic top view of the MEMS of FIG. 11 a; and

FIG. 12 is a schematic cross-sectional view of yet another known MEMS.

Detailed Description

Before embodiments of the invention are discussed in greater detail below on the basis of the drawings, it should be understood that functionally equivalent or equivalent elements, objects and/or structures in different drawings are provided with the same reference numerals, so that the description of these elements shown in the different embodiments is interchangeable or mutually applicable.

Reference is made below to MEMS transducers (MEMS ═ micro-electromechanical systems). A MEMS transducer may comprise one or more electro-active elements that produce a change, i.e., a transformation, of a mechanical element based on an applied electrical quantity (current, voltage, charge, or the like). This change may relate to, for example, a deformation, heating or tensioning of the mechanical component. Alternatively or additionally, mechanical impact to the component, such as deformation, heating or tensioning, may result in an electrical signal or information (voltage, current, charge, or the like) that may be detected at the electrical terminals of the component. Some materials or components have a reciprocity, which means that the effects are interchangeable. For example, piezoelectric materials can include the inverse piezoelectric effect (deformation based on an applied electrical signal) and the piezoelectric effect (providing a charge based on a deformation).

The embodiments described below are somewhat concerned with the fact that an electrode arrangement forms a movable element. Here, the movement of the movable element can be taken from a deformation of the electrode arrangement. For the sensing function by a possible reciprocity, an actuator configuration can be configured such that the electrode arrangement is macroscopically deformed along a lateral movement direction, i.e. an element or region can be moved along the lateral movement direction. The element or region may be, for example, a stringer end or a central region of a stringer structure. Microscopically, the deformable element may undergo a deformation perpendicular to the lateral direction of movement when deformed in the lateral direction of movement. The embodiments described subsequently relate to a macro approach.

Some of the embodiments described below relate to electrodes connected to each other via mechanical fasteners and configured to move based on an electrical potential. However, embodiments are not so limited and may include any type of beam structure that is configured to provide a force that is translated into movement via a mechanical fastener (actuator) in response to an actuation and/or to detect a deformation (sensor), such as by using piezoelectric or other actuated materials. The beams may be, for example, electrostatic, piezoelectric and/or thermomechanical electrodes that provide deformation based on an applied potential.

FIG. 1 shows a schematic cross-sectional view of a MEMS 10 in accordance with an embodiment. The MEMS 10 includes a substrate 12, the substrate 12 including, for example, a layer stack 14 of several individual layers, wherein the substrate 12 includes a cavity 16 disposed inside the substrate 12 by partially removing the individual layers.

The layer stack 14 may comprise several layers. For example, the layer stack 14 may include a first substrate layer 18₁In which an active layer or a device layer 24₁By means of an intermediate layer 22₁Arranged here, such as by bonding, with a layer sequence 18₁、22₁And 24₁For example, the layer stack may correspond to that shown in fig. 11a with respect to the materials used and/or the dimensions. Via a further intermediate layer 22₂A further active layer 24₂Portions of the layer stack may be formed. Via an intermediate layer 22₃And a further substrate layer 18₂Portions of the layer stack 24 may be formed. Layer sequence 18₂、22₃And 24₂For example, the layer sequence 18 can be mirrored at least with respect to the layer type and the layer sequence, possibly also with reference to size₁、22₁And 24₁So that the two half-layers are stacked by means of the intermediate layer 22₂Are connected to each other.

The shown layer stacks are shown here by way of example only. Substrate layer 18₁And 18₂For example, may correspond to layers 1002 and 1032. Here, the intermediate layer 22 may be formed₁、22₂And/or 22₃Formed as an intermediate layer 1006.

The layer stack 14 may include different layers and/or additional layers, and/or may not include one or more of the layers shown. Therefore, there is a possibility that the base material layer is not arranged18₁Or 18₂Or possibly via a different substrate, for example a printed circuit board or the same, where the further layers are arranged. Despite the absence of layer 18₁And/or 18₂The cavity 16 may still be obtained in the substrate 12.

By way of illustration, the MEMS 10 is configured such that two active layers 24₁And 24₂Through an intermediate layer 22₂Are connected to each other. Active layer 24₁And/or 24₂For example, conductive materials, such as doped semiconductor materials and/or metallic materials, may be included. The layered arrangement of the conductive layers enables a simple configuration, since the cavity 16 can be selectively isolated from the layer 24₁And 24₂Removed to obtain, and intermediate layer 22₂And the electrode structures 26a to 26e can be retained by an appropriate adjustment of the process. Alternatively, it is also possible to arrange the electrode structures 26a to 26f completely or partially in the cavity 16 by other measures or procedures, such as by being produced and/or positioned in the cavity 16. In that case, electrode structures 26 a-26 f may be formed with layer 24₁And layer 24₂The portions remaining in the substrate 12 are of different structures, i.e., the same may comprise different materials.

Substrate layer 18₁And 18₂May include an opening 28₁Or 28₂Each of which may provide a fluid inlet and/or a fluid outlet as described for openings 1026 and 1034.

Thus, MEMS 10 may include MEMS2000 through at least one additional layer formed as an active layer in accordance with the illustrated embodiment, and forming layer 24, for example₂。

The electrodes 26a,26b and 26c may be fixed to each other at discrete areas in an electrically insulating manner, such as described for the MEMS 1000 in fig. 11b, wherein partial elements of the resistor structure are arranged on at least two of the electrodes. In response to an electric potential between electrodes 26a and 26c, and/or in response to an electric potential between electrodes 26b and 26c, a movement of movable element 32 may be achieved along a movement direction 34 by mechanical fixings at discrete points, which may, for example, correspond to direction 1024 and may be arranged in the x/y plane of a cartesian x/y/z coordinate system. The x/y plane may be a claim defining in-plane movement along which the movement direction 34 occurs.

The electrodes 26d to 26f may be layers 24₂And is perpendicular to the layer 24₁Adjacent substrate planes x/y are arranged. The electrodes 26a to 26c at least partially form a first layer of the layer arrangement 36, wherein the electrodes 26d to 26f at least partially form a second layer of the layer arrangement 36.

In comparison to dimension 1016, although the gap 42 between the electrodes 26a and 26c or 26d and 26f₁And a gap 42 between electrodes 26b and 26c or 26e and 26f₂A dimension 38 of the movable layer arrangement 36 along the z-direction may still be enlarged, since the same procedure may be used, as in the MEMS2000, with the same or comparable dimensions. Gap dimension 42₁And 42₂An aspect ratio to the dimension of the electrodes 26a to 26c or 26d to 26f along the z-direction may be, for example, the same as or similar to that described for the MEMS2000, and may, for example, have a value of less than 40, particularly about 30. However, the actual effective aspect ratio may be higher because dimension 38 is provided by juxtaposing layers or electrodes 26 a-26 f without enlarging gap 42₁And 42₂To increase, e.g., double, along the z-direction.

Here, and via the intermediate layer 22₂A partial dimension or partial height 44 parallel to the z-direction of the MEMS 10 of the respective half-layer stack 14 in combination₁And 44₂May correspond approximately to a corresponding dimension of MEMS 1000 along the z-direction.

Here, the movement of one of the electrodes 26d to 26f can be achieved in different ways. By mechanically combining the electrode 26a with the electrode 26d, for example the electrode 26b with the electrode 26e and/or the electrode 26c with the electrode 26f in pairs, a corresponding movement of one of the other electrodes, which is firmly mechanically connected, can be obtained directly from the movement of the electrode 26a,26b or 26c of the movable element 32. Thus, the mechanical anchors 46 may be omitted in the layers of the electrodes 26d to 26f₁And 46₂Which may correspond to, for example, element 1022 of MEMS 1000. Alternatively or additionally, alsoCan also be in layer 24₂In which respective mechanical fasteners 46 are provided to mechanically secure the electrodes 26 d-26 f at discrete locations or regions. Thus, a further movable element is obtained, which may be via the intermediate layer 42₂Firmly mechanically connected to the movable element 32, wherein a corresponding connection may also be completely or partially omitted.

In other words, the ratio of L-NED height to L-NED gap may be doubled, for example, by bonding two device wafers 24₁And 24₂Is doubled, rather than by placing a device wafer (layer 22) and a lid wafer (layer 18)₁) The bonding is doubled as shown in fig. 1, such that fig. 1 shows two device wafers bonded such that the L-NED stringers are mechanically connected to each other. In this way, the aspect ratio of the L-NED actuator is doubled. This solution has several advantages:

in a micro-speaker, for example, doubling the aspect ratio can result in a 6dB increase in sound level;

doubling the L-NED height results in a higher flexural strength along the z-direction, which in turn results in a lower sensitivity to vertical (along the z-direction) pull-in effects and enables a high degree of design freedom. This may be, for example, to make the L-NED stringer longer, meaning that the same may have a high axial extent along the y-direction. Alternatively or additionally, the L-NED stringers may be clamped on one side rather than both sides, which is beneficial because L-NED stringers clamped on one side achieve greater deflection than L-NED stringers clamped on both sides, for example.

Although it is still possible, according to the known configuration, a cover is not absolutely necessary, which provides a saving of potential.

If, for example, reference is again made to a known MEMS according to FIG. 12, a loudspeaker or a pump is assisted by the layer 1006₂Bonding layers 1002, 1006₁And 1004 a device wafer (referred to as technology 1) and a lid wafer 1032 (referred to as technology 2). Here, two different techniques or production steps are required to produce the lid and device wafer. In contrast, the MEMS 10 according to FIG. 1 can be produced using only one of these techniques (technique 1),because of the joined two components (44)₁And 44₂) Are all device wafers and are therefore produced by the same technique 1. This means that the use of technique 2 can be omitted, which enables simple production. The role of the lid wafer now passes 18₂To be implemented.

It should be understood herein that terms such as cap or base are used merely to more distinguish individual elements of the MEMS described herein and are not limited to a particular design nor to an orientation of the layers in space. Further, it should be appreciated that the doubling of the dimension along the z-direction discussed by way of example is one of the possible configurations. Layer 24₁And 24₂May have the same or different dimensions, both with respect to the area in the substrate 12 and also with respect to the area in the cavity 16.

FIG. 2 shows a schematic cross-sectional view of a MEMS20 in accordance with an embodiment, with intermediate layer 22₂Is subjected to removal between the electrodes 26a,26b and 26c on the one hand, and between the electrodes 26d, 26e and 26f on the other hand.

As in MEMS 10, active layer 24₂Is structured as electrodes 26d, 26e and 26f arranged along a z-direction perpendicular to the substrate plane adjacent to the electrode 26a,26b or 26c, however, the electrodes 26d and 26f may be via mechanical fasteners 46₃Are firmly mechanically connected to each other at a discrete location, and the electrodes 26e and 26f may be secured to each other via mechanical fasteners 46₄Are mechanically connected to each other such that the intermediate layer 22 is missing or removed₂The layer arrangement 2 may comprise a movable element 32₁And 32₂Which results in the same or equivalent effective dimension 38 along the z-direction, but enables a different control of the movable element.

According to an embodiment, different potentials may be applied between electrodes 26a and 26c on the one hand and electrodes 26d and 26f on the other hand. Alternatively or additionally, different potentials may be applied between electrodes 26b and 26c on the one hand and electrodes 26e and 26f on the other hand, which may result in movable element 32₁And 32₂Different movements thereof. This means that the respective electrodes exhibit separation in terms of current and/or are only used, for example, in application-specific integrated circuitsContacts are made in an optional control member of one of the (ASICs).

In other words, the L-NED stringers of the top device wafer are not directly connected to the L-NED stringers of the bottom device wafer. The two L-NED stringers may be separately controlled.

FIG. 3a shows a MEMS 30 in accordance with an embodiment₁A schematic cross-sectional view of MEMS 10 and 20, wherein electrodes 26a and 26b and electrodes 26b and 26e are via intermediate layer 22₂An intermediate layer 22 connected to each other between the electrodes 26c and 26f₂Is completely or partially subject to removal or not disposed so as to space electrodes 26c and 26f from each other. This results in a joint movement of one of the electrodes 26a and 26d and 26b and 26e, so that the mechanical mounts 46 (not shown in fig. 3 a) can be arranged at any location, such as according to the configuration of fig. 2, wherein, for example, it is also possible to omit the individual mechanical mounts, since a movement transfer can also take place via the intermediate layer 22 between the electrodes₂This occurs.

FIG. 3b shows a MEMS 30 in accordance with an embodiment₂In which compared to the MEMS 30₁Intermediate layer 22₂Is disposed between electrodes 26c and 26f so as to securely mechanically connect the two electrodes, but is subject to removal between electrodes 26a and 26b and/or between electrodes 26b and 26 e. Some of the mechanical fasteners 46 shown in fig. 2 may also be omitted, for example, the mechanical fasteners between electrodes 26a and 26c and between electrodes 26e and 26f, or between electrodes 26b and 26c and between electrodes 26d and 26f may be omitted. A movement transfer may occur via a mechanically fixed connection between electrodes 26c and 26 f.

In other words, the L-NED stringers of the top device wafer may be only partially directly connected to the L-NED stringers of the bottom device wafer, only the middle electrode according to FIG. 3b and only the outer electrode according to FIG. 3 a.

Embodiments provide that at least one pair of electrodes 26a and 26d, electrodes 26b and 26e, and electrodes 26c and 26f are via an intermediate layer 22 disposed between the layers₂Any configuration that are firmly mechanically connected to each other.Optionally, this layer may also be completely subjected to removal as described based on fig. 2.

The MEMS 10, 20, 30 described above₁And 30₂Including two actively formed layers disposed or stacked on top of each other in order to increase the aspect ratio of dimension 38 to gap 42. Although these MEMS are illustrated by using two active layers, such as silicon oxide or silicon nitride or polymers or the same, connected to each other by an intermediate layer, embodiments are not limited thereto, but any number of additional further layers, such as three or more, four or more, five or more, can also be arranged.

In the following, reference is made to further embodiments of the invention in which the aspect ratio is increased by means of further layers which may be passive.

Fig. 4a shows a schematic cross-sectional view of a MEMS40 according to an embodiment, wherein the second layer of the movable layer arrangement 36 comprises a resistor structure 48, the resistor structure 48 being constituted, for example, by the base layer 18 remaining in, arranged in or not removed from the area of the cavity 16 and being connected to at least one of the electrodes 26a,26b and/or 26c, so as to provide an additional liquid resistance for the electrodes 26a,26b and 26 c. For example, the resistor structure 48 may be maintained during a selective etching process. Advantageously, an effective height 54 of movable element 32 may be increased by resistor structure 48, as compared to height 52 of electrodes 26a,26b, and 26c along the z-direction, which may correspond to height 1016, for example.

Dimension 52 may be, for example, between 1 μm and 1mm, preferably between 50 μm and 400 μm, and particularly preferably between 70 μm and 150 μm. Referring to FIG. 1, this may result in a dimension 38 that is approximately twice as large due to the addition of the intermediate layer 22₂It may have a size of several μm, such as 1 μm, 2 μm or 10 μm. In this way, the dimension 56 may also be at least 50 μm, at least 100 μm, or at least 200 μm.

Here, a height or dimension 56 of the resistor structure 48 may be very large, especially when considering a selective arrangement of the resistor structure 48 along an x-direction at a location of the y-axis. In this way, an aspect ratio for this is passedGaps or voids 58 between the substrate layer 18 and the resistor structure 48₁Illustratively, and/or 48 between the substrate layer 18 and the resistor structure 48₂The height 56 relative to the resistor structure 48 may also have a value with a constraint ratio of less than about 40, for example less than 35 or less than 30 or less, i.e., the dimension 52 may be greater than the gap 42₁And/or 42₂By this factor. Consider gap 58₁To 58₂The gap 42 between the electrodes 26a to 26c₁And/or 42₂Much larger, this aspect ratio may result in a dimension 56 along the z-direction that is much larger than dimension 52. Dimension 56 may also be referred to as a layer thickness of layer 18 in the region of the cavity, and thus, the resistor structure may be at least a factor of 2, at least 3, at least 4, or more larger than dimension 52 of layer 24 in the region of electrodes 26 a-26 c.

In other words, FIG. 4a shows an L-NED stringer with a rear structure that is placed under the middle electrode.

Despite the resistor structure in fig. 4a, in which one of the intermediate electrodes 26c of the movable element 32 is arranged, fig. 4b shows a schematic cross-sectional view of the MEMS40 with the resistor structure 48 firmly mechanically connected to the electrode 26 b. Alternatively or additionally, at least a portion of the resistor structure 48 may also be securely mechanically connected to the electrode 26a, such as via the intermediate layer 22.

The illustration according to fig. 4a and 4b may relate to different MEMS in which the resistor structure 48 is arranged on only one of the electrodes 26b or 26 c. Alternatively, the resistor structure 48 may also be structured such that the illustrations of fig. 4a and 4b show different positions along the y-axis, as will be shown in more detail below.

The resistor structure 48, or a part thereof, is firmly mechanically connected to the movable element 32, so that the resistor structure 48 moves together with the movable element 32.

In other words, fig. 4b shows the structure in cross-section after placement under the outer electrode.

Fig. 4c shows a schematic cross-sectional view of a MEMS 40' according to an embodiment, in which the movable element 32 comprises, in a plane of the electrodes 26 a-26 c, a piggyback element 62 in firm mechanical connection with the resistor structure 48, such as by part of the intermediate layer 22. The carrying element 62 may be composed of the same material as the layer 24, i.e. the electrodes 26a to 26c, but may also be composed of a different material. For example, a coupling element 64 providing mechanical fixation may be arranged between the electrode 26b, which is firmly mechanically connected with the piggyback element 62, and the piggyback element 62. The coupling element 64 may, for example, provide electrical insulation, however, it is optional. It is also possible that the coupling element 64 represents at least a local widening in the x-direction across at least one region in the y-direction, such as in the concept of a local thickening, which, however, may lead to an asymmetry in relation to the generated electrostatic force. Preferably, the carrying element 62 is arranged on a side of the electrode 26b facing away from the electrode 26 c. Alternatively, the carrying element 62 can also be firmly mechanically connected to the electrode 26a, preferably on a side facing away from the electrode 26 c. Both embodiments can also be combined and can be combined with the statements made with respect to the MEMS40, which means that the resistor structure 48 can be arranged completely or partially on the piggyback element 62.

The coupling element 64 and/or the local widening are preferably arrangeable in the y-direction in a region which is at most slightly deformed when the active element or the movable element 32 is deformed, which may be a region of maximum deflection of the movable element. This means that the coupling element 64 is preferably not arranged where a large material strain of the movable element occurs. The magnitude of the movement or strain between the at most slightly deformed region and the actively deformed region may provide, for example, a ratio of 2:1, 3:1, or 4: 1.

Similar to MEMS40, the distance between resistor structure 48 and the substrate, i.e., layer 18, may be greater than the through gap 42₁And 42₂The distance between the electrodes is described. The distance may preferably be at least a factor of three, preferably at least four or at least a factor of 16 greater than the second distance.

The resistor structure 48 may provide a fluid resistance to a fluid disposed in the cavity 16. Although MEMS40 and MEMS 40' are shown such that resistor structure 48 is disposed on only one side of electrode structures 26 a-26 c along the negative z-direction, these embodiments are also related to disposing the resistor structure along the positive z-direction. A further embodiment relates to a combination of the two implementation aspects such that a further resistor structure is arranged which is arranged on both sides along the positive z-direction and the negative z-direction of the layer 24 and the electrodes 26a to 26c, respectively.

To control a direction of movement of fluid out of the cavity 16, for example, an additional cap layer 18 such as shown in FIGS. 3a and 3b₁And/or 18₂Corresponding openings may be arranged and provided. Although the openings in the embodiments described herein are shown as part of the outer layers of the layer stack, alternatively or additionally, the openings may still be disposed laterally, e.g., at MEMS 10, 20, 30₁Or 30₂Layer 24 of₁And/or 24₂And/or in the layers 24 and/or 18 of the MEMS40 or 40'. This enables the omission of a corresponding cap layer and/or the other use of a corresponding silicon region with openings.

It should be noted that the mechanical fasteners 46 are not shown in fig. 4a, 4b and 4 c.

In other words, fig. 4c shows the structure in cross section after placement laterally to the electrodes.

FIG. 4d shows a schematic top view of a MEMS40 "in accordance with yet another embodiment, wherein the coupling elements 64 are arranged clamped to the substrate 12₁On a freely deflectable end of a movable element 32 on one side, the substrate 12₁Connecting the movable element or its freely deflectable end to a plurality of resistor structures 48₁、48₂Resistor structure 48₁、48₂A comb-like structure is formed movably in a cavity 65 of the cavity of the MEMS.

FIG. 4e shows a schematic cross-sectional view of the MEMS40 'of FIG. 4d in section A' A of FIG. 4d, where it is clearly visible that the movable element 32 is along adjacent a substrate 12₂And a wiping movement, such as over the substrate, parallel to the direction of movement 38. By having resistive elements 48 arranged, for example, by using intermediate layers 22₁、48₂And 48₃With the coupling element 64, the resistance element can also be moved in the cavity 65 of the cavity along the direction of movement 38. The recess 65 may pass through the substrate 12₂Along the x-directionLaterally constrained such that a corresponding aspect ratio or a dimension of the movable element 32 and/or its electrodes along the z-direction can be prevented. Base material 12₂For example, a dimension 67 of greater than 75 μm, greater than 150 μm, or greater than 300 μm, for example, and the resistor structure 48₁、48₂And 48₃The sizes are the same. This means that instead of a direct fluid interaction by means of the movable element 32, an indirect actuation or sensing via a comb structure is instead provided, due to the resistor structure 48₁To 48₃Distance 69 between₁And 69₂Large, resistor structure 48₁To 48₃Can be assembled into large resistor structures, respectively, while maintaining the corresponding aspect ratio. The coupling element 64 effects a transfer of the movement of the movable element 32 towards the comb structure.

In other words, the rear structure is fitted on a movable but undeformed portion of the coupling element 64, which moves at the deformed movable element NED.

Thus, an increase in stiffness in the lateral deflection direction for the deformed structure is effectively deactivated, i.e. prevented, so that no reduction in deflection occurs. However, the advantages of vertical pull-in effect or risk reduction are maintained. Here, it becomes effective to increase stiffness by the resistor structure. The connection of the NED to the rear structure is made via a coupling element. Here, the number of resistor structures in MEMS40 "is any number ≧ 1. A lateral dimension 71 of the comb-like structure along the direction of movement 38 may be larger than 150 μm, larger than 300 μm or larger than 600 μm, for example 725 μm.

FIG. 5a shows a schematic diagram of a MEMS 50 according to an embodiment, such as a top view from a bottom surface. Includes a mechanical fastener 46 that can pass through discrete locations₁To 46₈The movable elements of electrodes 26a,26b and 26c, which are mechanically firmly connected to each other, can be clamped firmly on both sides. The electrodes 26a and 26c may be electrically and/or galvanically connected to each other, for example, because they are formed from the same continuous layer 24. However, electrode 26 may be formed by using insulating region 66₁And 66₂While being electrically insulated from the electrodes 26a and 26b so as to be able toA potential different from that of the electrodes 26a and 26b is applied.

FIG. 5b shows a view of MEMS 50 comparable to FIG. 5a, with the movable element deflected in FIG. 5 b. A direction of deflection of the movable element, such as along the positive x-direction, is adjustable via the orientation of the mechanical fastener 46.

As described above and below with respect to fig. 4a, the resistor structure 48 may be securely mechanically connected to the electrode 26c and may move with the same. The view of FIG. 5b shows that deflection of the movable element can also result in deflection of the resistor structure 48, thereby moving a high degree of fluid as long as the MEMS 50 is an actuator operated MEMS. In an operational sensing mode, a low degree of movement of the fluid, i.e., a low force, may be sufficient to cause the illustrated deflection.

An axial extension of the electrodes 26a,26b and 26c and thus a dimension of the movable layer arrangement parallel to the substrate plane and perpendicular to the direction of movement 34, for example along y, may be at least a factor of 0.5, preferably at least 0.6, and particularly preferably at least 0.7, compared to a dimension of the movable layer arrangement along a thickness direction z. Alternatively or additionally, the dimension along y may have a value in the range of at least 10 μm and at most 5000 μm, preferably at least 100 μm and at most 2000 μm, especially preferably at least 400 μm and at most 1500 μm.

Although MEMS 50 is shown such that the movable element is clamped on two sides, clamping on one side is also possible.

In other words, the use of a resistor structure is an additional or alternative option to increase the efficiency of the NED device. In the illustrated case of an L-NED stringer, a common aspect ratio of less than 30 or about 30 may be used so that as small a NED gap 42 as possible is achieved. The embodiments are directed to additionally structuring a passive back structure or resistor structure at the front and/or back end of the L-NED stringer. The rear structure is partially or fully connected to the L-NED stringers. As the L-NED stringers move, the rear structure also moves, thereby, as the fluid moves, more liquid or air than through the L-NED stringers alone. Since the rear structure is directly connected to the L-NED electrodes, the shape of the rear structure is identical to the stringer itself during deflection of the L-NED stringer. This means that the deflection or bending of the rear structure may be exactly the same as one of the L-NED stringers.

The rear structure can be made substantially as tall as desired, i.e., dimension 56 can be of any size. The same may be, for example, as large as the thickness of the handle wafer, which means, for example, at least 300 μm, at least 500 μm or at least 600 μm or more, since the structure is no longer limited by the L-NED, i.e., narrow gaps and aspect ratios < 30. The rear structure can be structured in a simple manner from the rear end of the BSOI wafer by means of the wider gaps (trenches). The trench on the back-end is still subject to production specific limitations (e.g. a Bosch limitation with an aspect ratio < 30) since the trench can be made wider, especially when only one resistor structure is used along the trench direction, the same can also be etched deeper resulting in large dimensions 56. Obviously, the rear structure could also be produced underneath the outer L-NED electrode 26a or 26b, or even as a separate structure parallel to the L-NED stringer, as shown in FIG. 4 c. According to a non-limiting example, the L-NED height 52 may be 75 μm and the post-structure height may be 600 μm. Thus, a corresponding structure can move eight times as much air as compared to the L-NED structure alone. Illustrated as a miniature speaker, this corresponds to about 18dB more sound pressure level. This occurs under the assumption that the additional post-structure does not significantly affect the deflection of the L-NED stringer. To ensure this, the design of the embodiment is aimed at keeping the stiffness of the rear structure in the lateral direction, i.e. in the x-direction or in the direction of movement 34, as low as possible, which can be achieved, for example, by a resistor structure 48 being thin along this direction. An exemplary dimension of resistor structure 48 along direction 34 is, for example, at most 100 μm, at most 50 μm, or at most 1 μm. In order not to significantly affect the inertia and lateral flexural stiffness of the overall system, the rear structure can be made as thin as possible, as long as it has mechanical stability. Lateral deflection losses due to attaching the rear structure to the L-NED stringers may be alternatively or additionally compensated for by using longer dimensions along the y-direction, and/or by a softer clamp representing an additional degree of freedom in system design.

In other words, FIGS. 5a and 5b show top views from the bottom end with the L-NED stringers (clamped on both sides) shown in a resting state or a non-deflected state and a deflected state. The rear structure 48 just follows the movement and/or deflection/bending of the L-NED stringer.

Fig. 6a shows a schematic top view of a MEMS 60 according to an embodiment, wherein the movable element 32 is arranged clamped on one side, whereby a free end 68 of the flexure beam structure may have a larger deflection along the direction of movement 34 than a central area of the flexure beams of the MEMS 50 clamped on both sides.

Independently thereof, the MEMS 60 comprises means for reducing the stiffness of the resistor structure 48. To this end, the resistor structure may comprise any number or number of partial elements 48a to 48j, at least two, at least three, at least five or at least 10, etc., arranged on one or several electrodes 26a,26b and/or 26 c. In this way, for example, the partial elements 48a to 48j are arranged along an axial route on the central electrode 26c along the y-direction of the same. Based on the structuring of the resistor element 48, the partial elements 48a to 48j are spaced apart from each other by distances 72a to 72i, which results in a reduction of the stiffness, i.e. the amount of stiffness increase caused by the resistor structure is kept low or minimized. The distances 72a to 72j may be equal or different and may be, for example, at most 100 μm, at most 50 μm or at most 5 μm for preventing fluid loss or at least keeping it low when the partial elements 48a to 48j arranged perpendicular to the movement direction 34 along the axial extension direction y are moved along the movement direction 34.

According to alternative embodiments, some of the elements 48 a-48 j of the resistor structure 48 may all be firmly mechanically connected to the electrode 26a or to the electrode 26b or to the electrode 26 c.

FIG. 6b shows a schematic top view of a MEMS 60' in which some elements 48 a-48 i are disposed on at least two of electrodes 26a,26b, and 26c, in accordance with an embodiment in which some elements are disposed on each of electrodes 26a,26b, and 26 c. The partial elements are arranged in a distributed manner along the axial extension y in order to provide a fluidic resistance in the cavity. Arranging the same on the different electrodes 26a,26b and/or 26c results in a further degree of freedom, since the projections 48'a to 48' i of the partial elements 48a to 48i overlap in a plane 74 arranged parallel to the axial extension direction and perpendicular to the substrate plane, for example parallel to the y/z plane, i.e. without distance, as shown for the projections 48'a and 48' b, for example. Although the projections 48 'a-48' i may have some distance from adjacent projections, it is beneficial for adjacent projections to have an overlap.

And a fixing member 46₁To 46₈In contrast to FIG. 6a, which is arranged symmetrically between the electrodes 26 and 26c on the one hand and 26b and 26c on the other hand, the holder 46 in FIG. 6b₁To 46₇May be asymmetric, for example, to adjust an adaptation to the movement profile and/or load profile of the movable element.

Although the partial element 48a is arranged on the electrode 26a and the partial element 48b is arranged on the electrode 26b, a fluidic resistance is still achieved along the direction of movement 34. The stiffness reduction is achieved by dividing or segmenting. At the same time, however, the overlap 76 between the projections achieves low fluid loss. This is an optional feature when considering that projections 48'b and 48' c include, rather than overlap 76, preferably a distance 78 adjusted in correspondence with distances 72a through 72h to keep fluid losses low.

In other words, it is additionally possible to divide it along the rear structure to significantly reduce the contribution to the increase in stiffness in the direction of movement, thereby preventing lateral deflection. Here, the divisions are shown with interruptions, the fluid efficiency (preventing a significant acoustic short-circuit, possible attenuation adjustment) of which can be specifically adjusted by a corresponding geometrical choice (small gap, i.e. distance 72). In essence, it is beneficial to choose a sufficiently small gap. Due to the limitation of the aspect ratio and thus the given minimum break width and the corresponding fluid loss, it may be advantageous to attach the rear structure to the electrode alternately as shown in fig. 6b, so that a wall element is built up in a fluid-like manner, while due to the fact that the projections overlap, the stiffness may still be significantly reduced and the technical boundary conditions may be maintained.

In other words, fig. 6a and 6b show the structure after having a break. The structure of a micro-speaker or micro-pump based on a rear structure is shown, i.e. the rear structure of fig. 4 a-4 c may comprise a cover layer at the top and/or bottom end and may be provided with inlets and/or outlets.

FIG. 7a shows a MEMS 70 according to an embodiment₁By way of example, by means of a further intermediate layer or bonding layer 82₁And 82₂The cap layer 78 connected to the layer 18 or 24₁And 78₂To supplement the MEMS40 of figure 4 a. Layer 78₁And 78₂May be formed in the same manner as layer 18. Bonding layer 82₁And 82₂May be formed in the same or similar manner as intermediate layer 22. A distance 84 between the outer electrodes 26a and 26b of the movable element and the substrate 12 may be greater than the gap 42₁To 42₂Such that the height 52 is not substantially limited.

In other words, in a micro-speaker and/or micro-pump, the rear structure provides yet another important design advantage. As mentioned above, known micro-speakers, such as according to MEMS2000, suffer from the so-called vertical pull-in effect. This means that the drive voltage may not be so high that the L-NED stringers are pulled towards the top or bottom and into contact with the cap layer, i.e. a vertical pull-in effect occurs. The stronger the vertical stiffness of the L-NED structure along z, the higher the drive voltage can be without vertical pull-in occurring. Vertical pull-in is especially critical for L-NED stringers clamped on one side. In a normal condition, L-NED stringers clamped on one side deflect to a greater extent at least at the free end than stringers clamped on both sides of the center. However, this advantage may be partially lost when a smaller drive voltage is chosen due to the vertical pull-in effect than in a comparable L-NED stringer clamped on both sides.

The vertical stiffness of the L-NED structure may be primarily defined by the thickness/height, by the length of the L-NED stringers, and by the clamping. The thicker and shorter the stringer and/or the higher the stiffness of the clamp, the less sensitive the stringer is to vertical pull-in. However, as discussed, the thickness of an L-NED stringer of any size cannot be selected because the production process is correspondingly limited, such as by the Bosch procedure. The length of the stringer cannot be chosen too short, nor can the clamping stiffness be too low, since this will limit lateral deflection. This means that in order to achieve high deflection, long beams with low stiffness clamps are desirable for micro-speakers and micro-pumps with respect to design. However, this limits the drive voltage due to the vertical pull-in. Thus, the advantages already achieved in terms of deflection by the choice of long stringers and low stiffness may again be partly lost by the reduction in drive voltage due to the vertical pull-in effect.

The latter structure/resistor structure discussed provides a solution to the above-mentioned challenges. Since the post structure height can be chosen to be of any size, for example eight times larger than the L-NED stringer, the stiffness of the overall structure is significantly increased in the vertical direction by the post structure and dominates the overall stiffness. Thus, additional clearance is obtained for designing the length and/or clamping of the L-NED stringer. For example, to achieve greater lateral deflection, the stringers may be designed to be longer and the clamps may be designed to be more flexible. The resulting disadvantages with respect to the vertical pull-in effect are then compensated by the height of the rear structure. This advantage applies to both L-NED stringers clamped on one side and L-NED stringers clamped on both sides.

FIG. 7b shows a MEMS 70 according to an embodiment₂A schematic cross-sectional view of the cavity 16, wherein the opening 28 connects the cavity 16 to an external environment 88 outside the substrate 12₂Is arranged in a plane of the movable layer arrangement, which means that the same at least partly overlaps the resistor element 48 and/or the layer 24 of the electrodes 26a,26b and 26c and/or the intermediate layer 22. This laterally disposed opening may enable the use of the layer 78 for purposes other than an opening₂. Alternatively or additionally, the opening 28₁It may also be arranged laterally. A lateral arrangement of one or several openings is possible in all MEMS described herein without any limitation. Opening 28₁And 28₂Can also be arranged in the clamped region of a clamped beam on both sides in the region of the movable layer arrangement structure, or in the movable layer arrangementIn the region of the clamped and freely movable end of a stringer clamped on one side of the structure.

FIG. 8a shows a MEMS 80 according to an embodiment₁A schematic cross-sectional view of a combined bipolar and post structure or resistor structure. This can also be considered, for example, such that in MEMS 70₁The movable structures in the cavity 16 described above and below are also doubled and/or the MEMS 10, 20, 30 are made to be MEMS₁Or 30₂The resistor structure is additionally provided, or several resistor structures are provided. In this way, for example, via the intermediate layer 22₂Structured layer 24 in electrodes 26a,26b and 26c or 26d, 26e and 26f, which are fully or partially connected to each other₁And 24₂. Thus, it is achieved that the connection to the intermediate layer 22 is possible₂Two movable elements 32 firmly mechanically connected to each other₁And 32₂. A corresponding resistor structure 48₁Or 48₂Can be firmly mechanically connected to the corresponding movable element 32₁And 32₂Or may be part thereof. Here, a resistor structure 48₁And 48₂Can be configured in the same or different ways, for example by structuring into different numbers of partial regions, an arrangement of the resistor structures or partial regions thereof at different electrodes, and/or different dimensions along the z-direction, since for the movable element 32₁And 32₂All of the layers are possible.

MEMS 80₁Can be configured such that the movable element is attached to the first resistor structure 48₁And 48₂Are arranged adjacent to each other along a direction z perpendicular to the substrate plane with respect to the electrode arrangements 26a to 26c and 26d to 26 f.

FIG. 8b shows MEMS 80₂A schematic cross-sectional view of the movable element 32₁And 32₂For MEMS 80₁The relative orientations are interchanged so that the resistor structure 48₁And 48₂Are adjacent to each other and are located in the movable element 32₁And 32₂And electrode arrangement structures 26a to 26c and 26d to 26f are arranged along a z-direction perpendicular to the substrate plane. Although it is used forInterposed resistor structure 48₁And 48₂Intermediate layer 22 in between₂Is shown as being removed, and still may be for the resistor structure 48₁And 48₂Provide the same by mechanical fixation therebetween. However, in the illustrated variant, the resistor structure 48₁And 48₂Are movable relative to each other, which achieve different controls. Both resistor structures may be connected to an active structure that effects or controls this movement, such as via the movable element 32₁And 32₂To be connected. For the MEMS 80₁And 80₂And a control means is provided which can be configured to control the movable elements 32 individually or collectively₁And 32₂. Control means 86 may be provided for any of the other MEMS described herein to control the movable layer structure.

In other words, the idea of stacking electrodes and post-structures can be combined to achieve even higher sound pressure levels. Exemplary combinations are shown in fig. 8a and 8 b. This in turn doubles the movable volume, i.e. 6dB of additional volume can be achieved, as illustrated by the miniature loudspeaker. This means that the combination of the stack and the rear structure can theoretically increase the volume by about 25dB (2x9), where it is assumed that in this example said is 20 log (2x9) to 25dB, 2 being used to double the volume and 9 being a factor of the achieved total height (600+ 75)/75. In such a configuration according to fig. 8a, the vertical pull-in can even be completely eliminated. Rear structure 48₁And 48₂And a cover 78₁And 78₂When connected to ground, electrodynamic forces between the rear structure and the lid wafer are prevented, i.e. vertical pull-in can practically no longer occur.

Although fig. 8a and 8b show a stack of two L-NED-T actuators, where T indicates the shape of the electrode and resistor structure combination, this concept can be extended in any way, so that for example further additional electrode structures or L-NED actuators can be added.

FIG. 9 shows a schematic side cross-sectional view of a MEMS 100 in accordance with an embodiment in which electrodes or stringers 26a,26b and 26c are respectively offset from stringers or electrodes 26d, 26e and 26f, respectively, disposed in adjacent layers by a possible electrode individual offset 91₁、91₂And 91₃Wherein the offset may alternatively also have the same amount for two or several elements or may also point in different directions along the x-direction.

Layer 24₁And 24₂And a movable element 32 structured from these layers₁And 32₂For example via an intermediate layer 22₁And 22₂Are connected to each other. An embodiment includes distance 91₁、91₂And 91₃The same value need not be assumed, but may be.

FIG. 10 shows, in a cross-sectional view of an embodiment, a layer 24 structured in the form of stringers₁And 24₂A movable layer arrangement 36 is formed. Similar to fig. 9, stringer 91₁、91₂And 91₃The distance is at most 100. mu.m, preferably 50 μm, particularly preferably 5 μm.

Embodiments of the invention also make it possible to design the inlet and/or outlet laterally in the plane of the rear structure, so that the cover and base plane can be used for electrical signal distribution. In this way, a preferably increased packing density can be achieved.

Embodiments enable a high expansion of the lateral or crossover region, e.g., by a factor of 16, for an L-NED based actuator. For an inventive micro-speaker, this can produce a sound level of up to 24dB, which is a significant amount. In addition, this effect is also beneficial for the inventive micropump. Since the height of the overall structure is increased by the back structure, the vertical pull-in voltage is greatly increased. A higher pull-in voltage provides several design degrees of freedom, for example, making the L-NED length longer and clamping (on one or both sides) more flexible to achieve a greater NED deflection. In addition to pumps, speakers and microphones, other applications also relate to MEMS waveguides for high frequencies, especially in the THz range.

Although aspects have been described in the context of a device, it is to be understood that these aspects also represent a description of the corresponding method, such that a block or device of a device corresponds to a respective method step or a feature of a method step. Similarly, aspects described in the context of a method step also represent a description of details or characteristics of a corresponding block or a corresponding apparatus.

The above-described embodiments are merely illustrative of the principles of the present invention. It is understood that modifications and variations of the arrangements and details described herein will be apparent to those skilled in the art. It is therefore intended that the invention be limited only by the scope of the appended patent claims and not by the specific details presented herein for the purpose of illustration and description of the embodiments.