阅读说明：本技术 一种高灵敏度mems压电式麦克风 (High-sensitivity MEMS piezoelectric microphone ) 是由 孙成亮 胡博豪 吴志鹏 林炳辉 朱伟 王磊 周禹 于 2019-08-28 设计创作，主要内容包括：一种高灵敏度MEMS压电式麦克风,包括具有空腔的晶圆衬底和多个具有压电叠层结构的悬臂梁,所述悬臂梁包括固定端和悬置于空腔上方的自由端,所述悬臂梁为一端窄另一端宽的结构,较窄的一端为固定端；所述空腔的底面中心设置有固定柱,多个所述悬臂梁的固定端均连接在所述固定柱的顶面,相邻的所述悬臂梁之间均设置有间隙,且相邻悬臂梁的自由端均连接有能使悬臂梁同步振动的柔性弹性件,其中一个所述间隙内设置有用于引出所述悬臂梁电信号的连接段。本发明通过改变MEMS压电式麦克风内悬臂梁的结构形式,提高了麦克风的灵敏度和信噪比。(A high-sensitivity MEMS piezoelectric microphone comprises a wafer substrate with a cavity and a plurality of cantilever beams with piezoelectric laminated structures, wherein each cantilever beam comprises a fixed end and a free end suspended above the cavity, the cantilever beam is of a structure with a narrow end and a wide end, and the narrow end is the fixed end; the bottom surface center of cavity is provided with the fixed column, and a plurality of the stiff end of cantilever beam all connects the top surface of fixed column, and is adjacent all be provided with the clearance between the cantilever beam, and the free end of adjacent cantilever beam all is connected with the flexible elastic component that enables cantilever beam synchronous oscillation, one of them be provided with in the clearance and be used for drawing the linkage segment of cantilever beam signal of telecommunication. According to the invention, the sensitivity and the signal-to-noise ratio of the microphone are improved by changing the structural form of the cantilever beam in the MEMS piezoelectric microphone.)

1. A high sensitivity MEMS piezoelectric microphone comprising a wafer substrate having a cavity and a plurality of cantilever beams having a piezoelectric stack, the cantilever beams comprising a fixed end and a free end suspended above the cavity, characterized in that: the cantilever beam is of a structure with one narrow end and the other wide end, wherein the narrower end is a fixed end; the bottom surface center of cavity is provided with the fixed column, and a plurality of the stiff end of cantilever beam all connects the top surface of fixed column, and is adjacent all be provided with the clearance between the cantilever beam, and the free end of adjacent cantilever beam all is connected with the flexible elastic component that enables cantilever beam synchronous oscillation, one of them be provided with in the clearance and be used for drawing the linkage segment of cantilever beam signal of telecommunication.

2. The high sensitivity MEMS piezoelectric microphone of claim 1, wherein: the cantilever beams are of a trapezoidal structure, the number of the cantilever beams is four, and the four cantilever beams form a rectangular structure in a surrounding mode.

3. The high sensitivity MEMS piezoelectric microphone of claim 1, wherein: the cantilever beam is the trapezium structure, and its quantity is six, six the cantilever beam encloses into the hexagon structure.

4. A high sensitivity MEMS piezoelectric microphone according to claim 2 or 3, wherein: the wafer substrate is an SOI wafer substrate, the top surface of the fixed column and the cantilever beam are all made into a piezoelectric laminated structure of a single chip, and the piezoelectric laminated structure sequentially comprises a bottom electrode, a piezoelectric film and a top electrode from bottom to top.

5. The high sensitivity MEMS piezoelectric microphone of claim 4, wherein: the connecting section is connected with the piezoelectric laminated structure on the fixing column and the piezoelectric laminated structure on the wafer substrate, and a bottom extraction electrode for extracting an electric signal of the bottom electrode and a top extraction electrode for extracting an electric signal of the top electrode are respectively arranged on the outer side of the top surface of the wafer substrate.

6. The high sensitivity MEMS piezoelectric microphone of claim 5, wherein: an insulating layer is arranged between the bottom extraction electrode and the top electrode.

7. The high sensitivity MEMS piezoelectric microphone of claim 5, wherein: and the bottom electrodes and the top electrodes of the plurality of cantilever beams are connected in parallel.

8. The high sensitivity MEMS piezoelectric microphone of claim 1, wherein: the flexible elastic piece is of an elastic wave-shaped structure.

9. A high sensitivity MEMS piezoelectric microphone according to claim 2 or 3, wherein: the wafer substrate is a Si wafer substrate, the top surface of the fixed column and the cantilever beam are all manufactured into a piezoelectric laminated structure with double chips, and the piezoelectric laminated structure sequentially comprises a lower electrode, a first piezoelectric film, a middle electrode, a second piezoelectric film and an upper electrode from bottom to top.

Technical Field

The invention relates to the technical field of microphones, in particular to a high-sensitivity MEMS piezoelectric microphone.

Background

A microphone is a device that converts a sound signal into an electrical signal, and is widely used in devices such as a microphone, a mobile phone, a PC, and vehicle-mounted voice recognition. With long-term development, the performance indexes of the microphone are more focused on intellectualization, digitalization and miniaturization. Nowadays, the MEMS piezoelectric microphone technology is combined with the fields of aerospace, biomedicine, consumer electronics, information communication, military industry, and the like more and more closely, and higher requirements are put forward on the reliability and sensitivity of the microphone. At present, the capacitance type microphone occupies the main market share, but the piezoelectric type microphone has wide application in the field of future aeroacoustics due to the advantages of durability, high sensitivity, low noise, no need of external power supply for driving and the like.

In the structure of the conventional beam type piezoelectric microphone, the fixed end of the beam is arranged at the periphery of the vibration region, and the influence of air damping on the device performance is not fully considered in the design process, so that the sensitivity and the signal-to-noise ratio of the microphone are reduced. Patent CN201811650376 discloses a microphone, but the free end of the cantilever beam diaphragm in the disclosed technology fails to effectively absorb the sound wave energy to the maximum, and the energy loss is large, thereby causing the lack of sensitivity of such a microphone; patent CN201821645803 discloses a microphone, in which a cover film connected to free ends of cantilever beams is used to maintain synchronous vibration of the cantilever beams, so as to ensure stability of signal output of the microphone, but the amplitude of the cantilever beams cannot be maximized, and sensitivity of the microphone is reduced. Therefore, an improved cantilever beam structure is required to improve the performance of the microphone.

Disclosure of Invention

In order to solve the above problems, the present invention provides a high-sensitivity MEMS piezoelectric microphone, which has the following specific technical solution:

a high-sensitivity MEMS piezoelectric microphone comprises a wafer substrate with a cavity and a plurality of cantilever beams with piezoelectric laminated structures, wherein each cantilever beam comprises a fixed end and a free end suspended above the cavity, and is of a structure with one narrow end and the other wide end, and the narrower end is the fixed end; the bottom surface center of cavity is provided with the fixed column, and a plurality of the stiff end of cantilever beam all connects the top surface of fixed column, and is adjacent all be provided with the clearance between the cantilever beam, and the free end of adjacent cantilever beam all is connected with the flexible elastic component that enables cantilever beam synchronous oscillation, one of them be provided with in the clearance and be used for drawing the linkage segment of cantilever beam signal of telecommunication.

Furthermore, the cantilever beams are of a trapezoidal structure, the number of the cantilever beams is four, and the four cantilever beams form a rectangular structure in a surrounding mode.

Furthermore, the cantilever beam is the trapezium structure, and its quantity is six, six the cantilever beam encloses into the hexagon structure.

Furthermore, the wafer substrate is an SOI wafer substrate, the top surface of the fixed column and the cantilever beam are all made into a piezoelectric laminated structure of a single chip, and the piezoelectric laminated structure sequentially comprises a bottom electrode, a piezoelectric film and a top electrode from bottom to top.

Furthermore, the connecting section is connected with the piezoelectric laminated structure on the fixing column and the piezoelectric laminated structure on the wafer substrate, and a bottom extraction electrode for extracting an electric signal of the bottom electrode and a top extraction electrode for extracting an electric signal of the top electrode are respectively arranged on the outer side of the top surface of the wafer substrate.

Further, an insulating layer is arranged between the bottom extraction electrode and the top electrode.

Furthermore, the bottom electrodes and the top electrodes of the cantilever beams are connected in parallel.

Further, the flexible elastic member is of a wave-shaped structure with elasticity.

Furthermore, the wafer substrate is a Si wafer substrate, the top surface of the Si wafer substrate, the top surfaces of the fixed columns and the cantilever beam are all manufactured into a piezoelectric laminated structure with two chips, and the piezoelectric laminated structure sequentially comprises a lower electrode, a first piezoelectric film, a middle electrode, a second piezoelectric film and an upper electrode from bottom to top.

Has the advantages that:

according to the invention, the structural form of the cantilever beam in the MEMS piezoelectric microphone is changed, so that the sensitivity of the microphone is improved; meanwhile, the influence of air damping during the vibration of the cantilever beam is reduced, and the signal-to-noise ratio of the microphone is improved.

Drawings

Fig. 1 is a top view of a single-chip microphone with six cantilevers according to the present invention.

Fig. 2 is a top view of a single-chip microphone with four cantilever beams according to the present invention.

Fig. 3 is a cross-sectional view a-a of the single chip microphone of the present invention.

Fig. 4 is a B-B sectional view of the single chip microphone of the present invention.

Fig. 5 is a C-C sectional view of the single wafer microphone of the present invention.

Fig. 6 is a cross-sectional view of a twin-chip microphone according to the present invention.

In the figure: the SOI wafer substrate comprises an SOI wafer substrate 1, a first insulating layer 11, a transition layer 12, a second insulating layer 13, a cavity 14, a single-chip cantilever beam 2, a bottom electrode 21, a piezoelectric film 22, a top electrode 23, a gap 24, a fixed column 3, a connecting section 4, a flexible elastic part 5, a bottom extraction electrode 6, a third insulating layer 61, a top extraction electrode 7, a double-chip cantilever beam 8, a lower electrode 81, a first piezoelectric film 82, an intermediate electrode 83, a second piezoelectric film 84, an upper electrode 85, a first extraction electrode 86, a second extraction electrode 87, a fourth insulating layer 88 and a wafer substrate 9 Si.

Detailed Description

The invention is further described with reference to the following figures and specific embodiments:

as shown in fig. 1 to 5, a high-sensitivity MEMS piezoelectric microphone includes a wafer substrate having a cavity 14 and a plurality of cantilever beams having a piezoelectric stack structure, the cantilever beams including a fixed end and a free end suspended above the cavity 14, the cantilever beams having a structure with one narrow end and the other wide end, wherein the narrower end is the fixed end; the center of the bottom surface of the cavity 14 is provided with a fixed column 3, the fixed ends of a plurality of cantilever beams are connected to the top surface of the fixed column 3, gaps 24 are formed between every two adjacent cantilever beams, the free ends of the adjacent cantilever beams are connected with flexible elastic pieces 5 capable of enabling the cantilever beams to vibrate synchronously, and a connecting section 4 used for leading out an electric signal of the cantilever beams is arranged in one of the gaps 24.

As shown in fig. 1, in one embodiment, the cantilever beams are in a trapezoid structure, the number of the cantilever beams is four, and short sides of the trapezoid structure of the cantilever beams are uniformly and fixedly connected to the fixed column 3 (shown by a dotted line in the figure, which is a top view of the fixed column 3), so that the four cantilever beams form a rectangular structure.

In another embodiment, as shown in fig. 2, the cantilever beams are in a trapezoid structure, the number of the cantilever beams is six, and the short sides of the trapezoid structure of the cantilever beams are uniformly and fixedly connected to the fixed column 3 (shown by the dotted line in the figure, which is the top view of the fixed column 3), so that the six cantilever beams form a hexagonal structure.

It should be understood, however, that in other embodiments, the number of piezoelectric cantilever beams shown is any desired number, and the configuration is any shape, so long as the cantilever beams are configured to be narrow at one end and wide at the other end, and the narrow ends are uniformly connected to the fixed posts 3 to form the cantilever beams into regular shapes.

In this embodiment, six cantilever beams having a trapezoidal structure are enclosed to form a regular hexagonal structure.

In this embodiment, the method for manufacturing the single-wafer cantilever 2 includes:

the method comprises the following steps: the wafer substrate is an SOI (silicon on insulator) wafer substrate with a cavity 14, and comprises a first insulating layer 11, a transition layer 12 and a second insulating layer 13, wherein the first insulating layer 11 and the second insulating layer 13 are made of silicon, and the transition layer 12 is made of silicon dioxide.

Step two: and growing a piezoelectric laminated structure of single wafers which sequentially comprise a bottom electrode 21, a piezoelectric film 22 and a top electrode 23 from bottom to top on the top surface of the SOI wafer substrate 1 and the top surfaces of the fixed columns 3 in a deposition sputtering mode and the like, wherein the bottom electrode 21 is made of molybdenum, the piezoelectric film 22 is made of aluminum nitride, and the top electrode 23 is made of molybdenum.

Step three: further, the top electrode 23 is patterned, leaving the top electrode 23 near the fixed end.

Step four: and spin-coating photoresist on the upper surface of the device, cleaning and removing the photoresist at the part to be etched after exposure, and sequentially etching the top electrode 23, the piezoelectric film 22, the bottom electrode 21, the second insulating layer 13 and the transition layer 12 to form a gap 24 between the single-chip cantilever beam 2 and the adjacent single-chip cantilever beam 2.

As shown in fig. 2 and 4, the short sides of the trapezoid structures of the six single-chip cantilevers 2 formed after etching are fixed to the tops of the fixed columns 3, and the wide sides of the single-chip cantilevers 2 are suspended above the cavities 14 to form free ends. In the embodiment, the top electrode 23 on the cantilever beam 2 is processed by photolithography, only a portion of the top electrode 23 near the fixed end remains on the cantilever beam 2, when vibration occurs, the stress strain of the cantilever beam 2 is mainly concentrated on the portion near the fixed end, and the amount of charge generated on the upper and lower surfaces of the piezoelectric material is larger, so that the top electrode 23 is arranged to effectively increase the signal output of the microphone device. The area of the free end of the single-chip cantilever beam 2 relative to the fixed end is larger, and the single-chip cantilever beam 2 is opposite to the single-chip cantilever beam 2 structure arranged in a microphone product released by Vesper company, under the conditions of the same device area and the same sound wave intensity, the amplitude of vibration generated by sound waves received by the free end is larger, the single-chip cantilever beam 2 generates larger stress strain, the output electric signal is stronger, and the sensitivity is higher. Particularly, in order to weaken the signal crosstalk caused by asynchronous vibration of a plurality of single-chip cantilever beams 2, a flexible elastic part 5 is etched between the free ends of the adjacent single-chip cantilever beams 2, and the flexible elastic part 5 is arranged in a gap 24, so that the single-chip cantilever beams 2 can synchronously vibrate to generate vibration and weaken signal crosstalk; the flexible elastic part 5 and the single-chip cantilever beam 2 can be simultaneously manufactured by patterned etching.

As shown in fig. 2 and 3, one of the gaps 24 on the right side has a connecting segment 4 for leading out electrical signals, so that the connecting segment can lead out electrical signals on the single-chip cantilever beam 2 and the bottom electrode 21 and the top electrode 23 on the fixed post 3, the structure form of the structure is shown in fig. 3, a customized SOI wafer substrate 1 with a required cavity 14 is selected, the connecting segment 4 structure is left in the cavity 14 when the cavity 14 is etched, and the connecting segment 4 is used for connecting the piezoelectric laminated structure on the fixed post 3 and the outer part of the piezoelectric laminated structure of the SOI wafer substrate 1. A bottom extraction electrode 6 for extracting an electric signal of the bottom electrode 21 and a top extraction electrode 7 for extracting an electric signal of the top electrode 23 are respectively arranged on the top surface of the SOI wafer substrate 1 close to the outer side, so that the electric signals are output; electric signals generated on the single-chip cantilever beams 2 and the fixed columns 3 are led out through the connecting sections 4, the bottom electrode 21 of each single-chip cantilever beam 2 is connected with the bottom lead-out electrode 6, and the top electrode 23 is connected with the top lead-out electrode 7, so that the single-chip cantilever beams 2 are connected in parallel. As shown in fig. 3 and 5, when the electrical signals of the bottom electrode 21 and the top electrode 23 are extracted, a third insulating layer 61 is deposited on the upper surface of the top electrode 23 on the top surface of the SOI wafer substrate 1, and then etched to a certain depth to expose the bottom electrode 21 and the top electrode 23, and then a metal layer is deposited, and further the metal layer is patterned by photolithography to form a top extraction electrode 7 and a bottom extraction electrode 6, wherein the material of the third insulating layer 61 is silicon dioxide, and the materials of the top extraction electrode 7 and the bottom extraction electrode 6 may be aluminum, gold, and the like.

As shown in fig. 4, an acoustic signal propagates to the microphone through a medium such as air, causing vibration of the monolithic cantilever 2, the piezoelectric film 22 in the monolithic cantilever 2 generates charges of opposite sign on the upper and lower surfaces thereof due to a positive piezoelectric effect, and an electrical signal is extracted through the bottom electrode 21 and the top electrode 23. A gap 24 with a certain width is reserved between the adjacent single-chip cantilever beams 2, so that the influence of air damping when the single-chip cantilever beams 2 vibrate can be reduced, meanwhile, the interference of air vibration in the cavity 14 to the vibration of the single-chip cantilever beams 2 is reduced, and the signal-to-noise ratio of the microphone device is improved.

In another embodiment, as shown in fig. 6, the cantilever of the MEMS piezoelectric microphone can be fabricated as a bimorph cantilever 8; specifically, the MEMS piezoelectric microphone comprises a Si wafer substrate 9, a lower electrode 81, a first piezoelectric film 82, a middle electrode 83, a second piezoelectric film 84, and an upper electrode 85 are formed on a top surface of the Si wafer substrate 9 from bottom to top by means of deposition sputtering or the like, a cavity 14 with a fixed column 3 remaining at the center, a plurality of bimorph cantilevers 8, a gap 24 between adjacent bimorph cantilevers 8, and a flexible elastic member 5 connected to a free end of the adjacent bimorph cantilever 8 and capable of synchronously vibrating the bimorph cantilever 8 are formed by etching, the lower electrode 81 and the upper electrode 85 of the bimorph cantilever 8 are connected in parallel, a connection segment 4 for leading out an electrical signal is provided in one of the gaps 24, and the connection segment 4 is integrally formed with the fixed column 3 and the Si wafer substrate 9 by etching. During the vibration of the bimorph cantilever beam 8, the structural layer with zero stress strain is called the neutral axis, the neutral axis of the bimorph cantilever beam 8 is located in the middle electrode 83, and the stress strain at the upper part of the neutral axis is opposite to that at the lower part; when the bimorph cantilever 8 vibrates, the stress strains of the first piezoelectric film 82 and the second piezoelectric film 84 are opposite, the polarization directions of the two piezoelectric films 22 are the same, the signs of the charges generated on the two surfaces of the first piezoelectric film 84 and the second piezoelectric film 84 which are in contact with the intermediate electrode 83 are the same, and the signs of the charges generated on the lower surface of the first piezoelectric film 82 and the upper surface of the second piezoelectric film 84 are the same. By the distribution characteristics of the generated charges, when the electrodes are led out, the electric signals of the lower electrode 81 and the upper electrode 85 are led out through the first lead-out electrode 86, the electric signal of the middle electrode 83 is led out through the second lead-out electrode 87, and a fourth insulating layer 88 isolated from the upper electrode 85 is arranged below the second lead-out electrode 87; the first extraction electrode 86 and the second extraction electrode 87 are disposed outside the top of the Si wafer substrate 9. By adopting the double-wafer cantilever beam 8 and utilizing the signal superposition of the characteristics, the signal output of the MEMS piezoelectric microphone can be obviously increased, and the sensitivity of the device is improved. It should be understood, however, that the structure of the dual-chip cantilever 8 fabricated using the Si wafer substrate 9 is similar to the structure of the single-chip cantilever 2 fabricated using the SOI wafer substrate 1, not described in detail.

The technical scheme provided by the invention can effectively improve the sensitivity and the signal-to-noise ratio of the piezoelectric microphone, and the provided novel structure has simple manufacturing process, is compatible with a CMOS (complementary metal oxide semiconductor) process and is convenient for mass production of the miniature microphone.