阅读说明：本技术 压力传感器 (Pressure sensor ) 是由 塔皮奥·珀努 尤卡·凯纳琳 雅克·萨里拉赫蒂 于 2019-09-12 设计创作，主要内容包括：根据本发明的示例方面,提供了一种MEMS压力传感器(1),其包括：传感器部分(10)和阀部分(20),传感器部分(10)包括可变形膜(11)和第一腔室(12),阀部分包括到压力传感器的第一侧(40)的第一输出(22)和到压力传感器的第二侧(50)的第二输出(23)。所述阀部分可操作以关闭第二输出并打开第一输出,使第一腔室中的压力与所述压力传感器的第一侧的压力相等,从而用于校准传感器；关闭第一输出,打开第二输出,使第一腔室中的压力与压力传感器的第二侧的压力相等,从而进行压力测量。(According to an example aspect of the invention, there is provided a MEMS pressure sensor (1) comprising: a sensor portion (10) and a valve portion (20), the sensor portion (10) comprising a deformable membrane (11) and a first chamber (12), the valve portion comprising a first output (22) to a first side (40) of the pressure sensor and a second output (23) to a second side (50) of the pressure sensor. The valve portion operable to close the second output and open the first output to equalize the pressure in the first chamber with the pressure on the first side of the pressure sensor for calibration of the sensor; the first output is closed and the second output is opened to equalize the pressure in the first chamber with the pressure on the second side of the pressure sensor, thereby making a pressure measurement.)

1. A MEMS pressure sensor (1) comprising:

a sensor portion (10) comprising a deformable membrane (11) and a first chamber (12),

-a valve portion (20) comprising a first output (22) to a first side (40) of the pressure sensor and a second output (23) to a second side (50) of the pressure sensor, wherein the valve portion is operable to:

o closing the second output and opening the first output to equalize the pressure in the first chamber with the pressure on the first side of the pressure sensor, thereby calibrating the pressure sensor; and

o closing the first output and opening the second output to equalize the pressure in the first chamber with the pressure on the second side of the pressure sensor, thereby making a pressure measurement.

2. The MEMS pressure sensor (1) of claim 1, wherein the valve portion comprises a second chamber (21) connected to the first chamber (12), a first membrane (24) comprising the first output (22), a second membrane (25) comprising at least a portion of the second output (23), and a third membrane (26) located within the second chamber and between the first and second membranes, wherein the third membrane is adjustable to close the first output to measure pressure, the third membrane is adjustable to close the second output to offset zero.

3. The MEMS pressure sensor (1) according to claim 2, characterized in that the sensor is configured to modulate the third membrane to switch off a first output by applying a first voltage between the first and third membranes, and the sensor is configured to modulate the third membrane to switch off the second output by applying a second voltage between the second and third membranes.

4. The MEMS pressure sensor (1) according to any preceding claim, characterized in that the pressure sensor is a capacitive pressure sensor and comprises a first electrode (13) in the first chamber and a second electrode (14) forming or comprising the deformable membrane.

5. The MEMS pressure sensor (1) of claim 4, further comprising a third electrode (15), wherein the electrodes are electrically insulated from each other, the second electrode is located between the first electrode and the third electrode, and the third electrode is configured such that a pressure of a first side of the pressure sensor affects the deformable membrane.

6. The MEMS pressure sensor (1) according to claim 5, characterized in that the pressure sensor is configured to detect a pressure difference based on a capacitance imbalance between a first capacitance between the second electrode and the third electrode and a second capacitance between the second electrode and the first electrode during the pressure measurement.

7. The MEMS pressure sensor (1) according to any one of claims 1 to 3, characterized in that the pressure sensor is a piezoresistive pressure sensor and comprises at least one piezoresistive membrane on or comprising a deformable membrane.

8. The MEMS pressure sensor (1) of claim 7, wherein the piezoresistive membrane comprises a piezoresistive group on a deformable membrane configured to provide a signal indicative of a change in electrical resistivity when the first output is closed and the second output is opened.

9. A device comprising a MEMS pressure sensor (1) according to any of the preceding claims and a control circuit configured to cause the first and second outputs to be turned off and to detect a pressure difference between a first and a second side of the pressure sensor.

10. Method for operating a MEMS pressure sensor (1, 60) according to any of the claims 1 to 9, comprising:

-directing a first output (22) of the sensor to open and a second output (23) of the pressure sensor to close to equalize the pressure in the first chamber (12) with the pressure of a first side (40) of the pressure sensor,

-receiving a first signal indicative of a change in capacitance or resistance associated with a deformable membrane (11, 71) of the pressure sensor after opening the first output and closing the second output (23),

-performing a sensor calibration based on the received first signal,

-directing the closing of the first output (22) and the opening of the second output (23) after sensor calibration to equalize the pressure in the first chamber (12) with the pressure at the second side (50) of the pressure sensor,

-after closing the first output (22) and opening the second output (23), receiving a second signal indicative of a change in capacitance or resistance associated with the deformable membrane (11, 71); and

-determining a pressure difference between the first side and the second side of the pressure sensor from the received second signal.

11. Method for operating a MEMS pressure sensor according to claim 2, characterized in that the third membrane is directed to close the first output for pressure measurement and to close the second output for offset zeroing.

12. The method of claim 11, wherein the third membrane is directed to turn off a first output by applying a first voltage between the first membrane and the third membrane, and wherein the third membrane is directed to turn off a second output by applying a second voltage between the second membrane and the third membrane.

13. A control device comprising means configured to perform the method of any one of claims 10 to 12.

Technical Field

The invention belongs to a pressure sensor. In particular, the present invention pertains to microelectromechanical (MEMS) pressure sensors.

Technical Field

MEMS technology facilitates the fabrication of compact pressure sensors, such as piezoresistive pressure sensors. Piezoresistive sensors may consist of piezoresistive detection elements on a deformable membrane. The change in the geometry of the deformable membrane caused by the pressure causes the sensor to detect the change in resistivity.

MEMS capacitive pressure sensors require two electrodes that move relative to each other under the application of pressure. This configuration is typically achieved by providing a fixed electrode on the substrate, while a moving electrode is provided in a deformable membrane that is exposed to the pressure to be sensed.

WO2016203106 discloses a MEMS capacitive pressure sensor comprising a first electrode, a deformable second electrode, the second electrode being electrically insulated from the first electrode by a cavity between the first electrode and the second electrode. At least one of the first electrode and the second electrode includes at least one pedestal protruding into the chamber. A method for manufacturing a MEMS capacitive pressure sensor is also provided.

Pressure sensors are susceptible to drift over time. The external valve is used to compensate for drift of the differential pressure sensor.

Disclosure of Invention

According to some aspects, the invention provides the subject matter of the independent claims. Some specific embodiments are defined in the dependent claims.

According to a first aspect of the present invention, there is provided a MEMS pressure sensor comprising: a sensor portion comprising a deformable membrane and a first chamber; and a valve portion including a first output to a first side of the pressure sensor and a second output to a second side of the pressure sensor. The valve portion being operable to close the second output and open the first output to equalize the pressure in the first chamber with the pressure on the first side of the pressure sensor to thereby calibrate the pressure sensor; and closing the first output and opening the second output to equalize the pressure in the first chamber with the pressure on the second side of the pressure sensor to make a pressure measurement.

According to a second aspect of the invention, there is provided a method for operating a MEMS pressure sensor according to the first aspect, comprising:

directing the opening of a first output of the sensor and the closing of a second output of the pressure sensor to equalize the pressure in the first chamber with the pressure on the first side of the pressure sensor,

-receiving a first signal after opening the first output and closing the second output, the first signal being indicative of a capacitance or resistance change associated with the deformable membrane of the pressure sensor,

-performing a sensor calibration based on the received first signal,

directing the first output to be closed and the second output to be opened after calibration of the sensor to equalize the pressure in the first chamber with the pressure on the second side of the pressure sensor,

-after closing the first output and opening the second output, receiving a second signal indicative of a capacitance or resistance change associated with the deformable membrane; and

-determining a pressure difference between the first side and the second side of the pressure sensor based on the received second signal.

According to one embodiment, the valve portion comprises a second chamber connected to the first chamber, a first membrane comprising the first output, a second membrane comprising at least a portion of the second output, and a third membrane located within the second chamber and between the first membrane and the second membrane, wherein the third membrane is adjustable to close the first output of the pressure measurement, and the third membrane is adjustable to close the second output to offset zero.

According to one embodiment, the sensor is configured to regulate the third membrane to turn off the first output by applying a first voltage between the first membrane and the third membrane, and the sensor is configured to regulate the third membrane to turn off the second output by applying a second voltage between the second membrane and the third membrane.

According to one embodiment, the pressure sensor is a capacitive pressure sensor and comprises a first electrode in the first chamber and a second electrode forming or comprising the deformable membrane.

According to one embodiment, the pressure sensor is configured or comprised to provide a first signal indicative of a change in capacitance or resistance associated with the deformable membrane of the pressure sensor after opening the first output and closing the second output. After closing the first output and opening the second output, a second signal indicative of a change in capacitance or resistance associated with a deformable membrane of the pressure sensor is provided.

Drawings

FIGS. 1 and 2 illustrate cross-sectional or side views of a MEMS pressure sensor in accordance with at least some embodiments of the present invention;

FIGS. 3 and 4 illustrate side views of a capacitive MEMS pressure sensor in accordance with at least some embodiments of the present invention;

FIG. 5 illustrates a top view of a capacitive MEMS pressure sensor in accordance with at least some embodiments of the present invention;

FIG. 6 illustrates a side view of a piezoresistive MEMS pressure sensor, in accordance with at least some embodiments of the present invention;

FIG. 7 illustrates a top view of a piezoresistive MEMS pressure sensor, in accordance with at least some embodiments of the present invention;

FIGS. 8 and 9 illustrate side views of piezoresistive MEMS pressure sensors in accordance with at least some embodiments of the present invention;

FIG. 10 is a flow chart of a method in accordance with at least some embodiments of the present invention.

Detailed Description

A MEMS pressure sensor apparatus or device is now provided in which an integrated valve device has been developed to account for drift of the sensor. The size of the valve has been reduced to MEMS size, thereby also greatly reducing the costs associated with drift compensation. The valve may also be referred to as an integrated MEMS valve and is used with a MEMS pressure sensor portion to compensate for drift and offset nulling.

Fig. 1 shows a simplified embodiment of such a MEMS pressure sensor device 1. The sensor device 1 comprises a sensor portion 10, which sensor portion 10 comprises a deformable membrane 11 and a first chamber 12. The sensor device further comprises a valve device or portion 20, which valve device or portion 20 comprises a second chamber 21 connected to the first chamber by a channel 29, a first output 22 connected to one side 40 of the pressure sensor and a second output 23 connected to the other side 50 of the pressure sensor.

The valve portion 20 may include: a first membrane 24 comprising the first output 22, a second membrane 25 comprising at least a portion of the second output 23, and a third membrane 26, the third membrane 26 being located in the second chamber 21 and between the first and second membranes. For example, the third membrane may be spring mounted to another portion of the intermediate layer 28. The layer 28 may extend to the sensor portion 10 and may include the deformable membrane 11. Valve portion 20 may further include a third chamber 27 connected to or including second output 23.

The sensor 1 further comprises a first electrode 13, which may be fixedly attached to the substrate 2, either directly or via one or more intermediate layers. The substrate 2 may be a standard silicon wafer. The substrate may further include a semiconductor device (not shown).

As shown in fig. 1 and 3, the third diaphragm 26 is adjustable to close the first output 22 and open the second output 23 for pressure measurement. Thus, via the channel 29, the second chamber 21, the second output 23 and the third chamber 27, a channel is opened from the chamber 12 to the other side 50 of the sensor device, so that the pressure in the chamber 12 equals the pressure p 2. This state of the valve part and the sensor 1 may be referred to as a measuring mode. The pressure difference between the different sides 40, 50 of the pressure sensor 1 causes deflection of the deformable membrane 11. As further shown in fig. 3 and 4, the third film 26 is insulated from the first and second films 24, 25, for example, by thin insulating films 30, 31 attached to the third and/or other films 24, 25.

The valve portion 20 may form an electrostatically actuated MEMS valve. In some embodiments, sensor device 1 is configured to regulate third membrane 26 to turn off first output 22 by applying a first voltage (coupled to layer 28 or forming a portion of layer 28) between first membrane 24 and third membrane 26.

As shown in fig. 2 and 4, the third membrane 26 is adjustable to open the first output 22 and close the second output 23 for calibration of the sensor and offset zeroing, referred to herein as a calibration mode. Referring to fig. 4, when entering the calibration mode, the pressure in the first chamber V112 is equal to the pressure p1 in the first side 40 through the flow path defined by the conductances Ca, Cb and Cc.

In some embodiments, the sensor device is configured to regulate the third membrane 26 to turn off the second output 23 by applying a second voltage between the second membrane 25 and the third membrane 26. Depending on the chosen implementation, the first voltage may be equal to or different from the second voltage. In an alternative embodiment, the sensor device is configured to apply only a voltage to switch to the measurement mode or the calibration mode. The sensor device may be configured such that power needs to be supplied only when the state of the valve portion 20 changes. The power consumption required for the actuation is in the mW range, possibly even in the μ W range, thus enabling a substantial reduction in energy consumption compared to the application of conventional external (three-way) valves requiring power supply when the valve is in the actuated state (in the W range).

According to some embodiments, the pressure sensor 1 is a capacitive pressure sensor. Referring to the example of fig. 1 to 4, a capacitive sensor device 300 and its sensor portion 10 comprise a first electrode 13 in a first chamber and a second electrode 14 forming or comprising a deformable membrane 11. The sensor device 300 further comprises a third electrode 15, the third electrode 15 being configured such that a pressure at the first side 40 of the pressure sensor influences the second electrode and thereby the deformable membrane 11. The electrodes are electrically insulated from each other by an insulating layer.

The pressure difference during the measurement mode shown in fig. 3 is proportional to the capacitance imbalance between the first capacitance C1 between the second electrode 14 and the third electrode 15 and the second capacitance C2 between the second electrode 14 and the first electrode 13. Therefore, the voltage difference pl-p2 can be derived based on the capacitance imbalance C1-C2 or C1/C2.

Fig. 5 shows a top view embodiment of the capacitive pressure sensor 1.

In some embodiments, the pressure sensor is a piezoresistive pressure sensor. The sensor may thus comprise at least one piezoresistive detection element on the deformable membrane, or alternatively a deformable membrane. The piezoresistive detection elements may include a thin conductive film embedded between insulating layers. For example, the diaphragm may be single crystal or polycrystalline silicon. In the measurement mode, the diaphragm stretches when external pressure is applied to the diaphragm. The geometric changes (compression or tension) cause changes in the resistivity of the membrane. The piezoresistive pressure sensor is configured to detect a resistance change in the diaphragm and provide a signal for pressure measurement based on the resistance change.

Some embodiments of such piezoresistive pressure sensors are provided in fig. 6 to 9. Fig. 7 shows a top view embodiment of a piezoresistive pressure sensor 60. Fig. 8 and 9 show the measurement and calibration modes of the pressure sensor 60, respectively.

Sensor 60 includes a valve arrangement or valve portion that may include similar elements and operate similarly to valve portion 20 described above. As shown in fig. 6, in some embodiments, the valve portion may be disposed in a particular third intermediate position, which may be used as a rest position/mode. However, in other embodiments, the valve portion may be provided with two positions and modes, one of which may be used as the rest position (no power supply is required).

The sensor 60 includes a sensor portion 70 configured for piezoresistive pressure measurement. The sensor portion 70 includes a deformable film 71 and a group of piezoresistors 72 on the deformable film 71. A set of piezo-resistor groups 72 is configured to provide a signal indicative of a change in resistivity when the first output 22 is turned off and the second output 23 is turned on. In the measurement mode, the deformation member 71 in the piezoresistive pressure sensor 60 bends causing a change in resistance, and the pressure difference is proportional to the change in resistance sensed by the piezoresistor 72. The sensor may thus be configured to output a signal indicative of the pressure differential between the first chamber 12 and the third chamber 27. The piezoresistive pressure sensor may be calibrated by the upper valve portion 20, as shown in fig. 9. The signal conditioning circuit may be used for temperature compensation.

The presently disclosed MEMS sensor with integrated calibration valve apparatus may have a number of advantages. The size and power consumption of the overall sensor device with drift compensation can be greatly reduced. The use of associated ports and piping can be avoided since the use of external valves can be avoided. Gas change and calibration is faster due to the shorter distance. Furthermore, the overall production costs can be reduced by the integrated manufacture of the sensor part 10, 70 and the valve part 20.

Some example application areas of the presently disclosed MEMS sensor with integrated calibration valve arrangement include building automation and medical equipment, such as differential pressure transmitters for heating, ventilation and air conditioning (HVAC) systems and breath analyzers.

It should be understood that fig. 1-9 illustrate only some sensor device embodiments and that various modifications and additions to the structure may be made. It will also be appreciated that the form and location of the sensor device elements, such as the number and location of connections and/or outputs between chambers, may be varied in a number of ways depending on the application in question.

According to some embodiments, a device is provided, which comprises and/or controls a MEMS sensor apparatus 1, 60 according to any of the embodiments described above. The apparatus also includes control circuitry configured to control the MEMS sensor device, e.g., to cause the first and second outputs to close, and to detect a pressure differential between the first and third chambers. In some implementations, the circuitry includes one or more Application Specific Integrated Circuits (ASICs) or Field Programmable Gate Arrays (FPGAs). The apparatus may comprise a control device configured to control the MEMS sensor device 1, 60 and to receive signals from the sensor device for pressure measurement.

According to at least some embodiments, the electronic circuit may constitute an electronic device configured as a control device to control the operation of the MEMS sensor device 1, 60. In some embodiments, a device that performs at least some of the functions described above is included in such an apparatus, for example. The apparatus may comprise circuitry such as a chip, chipset, microcontroller or a combination of circuitry for or in any of the above devices. The circuitry may refer to the use of a purely hardware circuitry implementation or a combination of hardware circuitry and a software implementation. The apparatus may include a processor and a memory at least partially accessible by the processor. The memory may include computer instructions configured to be executable by the processor. The memory, processor, and computer program code may thus be configured to cause the apparatus to perform at least some of the features of the present disclosure. It will be appreciated that the apparatus may comprise various other elements, such as a transmitter for transmitting the measurement results, a receiver and a user interface.

Referring to fig. 10, according to an aspect, a method for operating a MEMS pressure sensor device according to at least some of the above illustrated embodiments is provided. The method may measure the pressure with the sensor device 1 or 60 by means of an apparatus comprising or controlling the MEMS sensor device 1, 60. The method comprises the following steps:

100 directing the opening of the first output 22 of the sensor means and closing the second output 23 of the sensor means to equalize the pressure in the first chamber 12 with the pressure at the first side 40 of the sensor means,

-110, after opening the first output and closing the second output 23, receiving a first signal indicative of a change in capacitance or resistance associated with the deformable membrane 11, 71 of the sensor device,

-120, performing a sensor calibration on the basis of the received first signal,

130 instructing to close the first output 22 and to open the second output 23 after calibration of the sensor to equalize the pressure in the first chamber 12 with the pressure at the second side (50) of the sensor device,

-140, after closing the first output 22 and opening the second output 23, receiving a second signal indicative of a change in capacitance or resistance associated with the deformable membrane 11, 71; and

-150, determining a pressure difference between the first side 40 and the second side 50 of the sensor device based on the received second signal.

The MEMS pressure sensor 1, 60 with integrated valve device may be manufactured, for example, by applying at least some of the features of the manufacturing process shown below. The fabrication process is based on micromechanical polysilicon deposition and sacrificial etching of a supporting oxide layer. Sacrificial etching refers to the partial removal of the silicon oxide layer between and below the polycrystalline films during processing to release the films and form free-standing structures. The main benefits of using polysilicon include uniformity of the deposition process, adaptable tensile stress, electrical conductivity, and chemical selectivity to silicon dioxide during sacrificial etching.

In the case of the capacitive sensor device 1, the pressure sensitive element may be constituted by two separate, overlapping air gap capacitors fabricated on a thin DSP silicon wafer. The capacitor is formed by a curved diaphragm 11 which is open to the external air pressure and has two stationary perforated electrodes 13, 15 below and above the diaphragm. The pressure differential causes the diaphragm to flex, causing the capacitance to change in proportion to the pressure differential.

The diaphragm and electrodes may be deposited from thin micromachined polysilicon. Three dielectric silicon oxide layers support the polysilicon film and act as electrical insulators between the diaphragm and the electrodes. The support area of the static electrode is minimized to keep the parasitic capacitance low. The back side of the silicon substrate is subjected to DRIE (deep reactive ion etching) etching to release the bottom electrode.

Hydrogen fluoride vapor may be applied on both sides simultaneously to remove portions of the supported silicon oxide layer. The geometry of the capacitor cavity is defined by lithographically defined openings in the electrostatic electrodes during the sacrificial etch. An electrical connection is formed over the subsequently opened contact opening using aluminum metallization. The top surface is passivated with a silicon oxide and nitride layer.

The two-way and three-way electrostatically actuated MEMS valve part 20 can be manufactured by the same manufacturing process as the pressure sensor. The structure of the valve is very similar to the pressure sensor portion 10, which pressure sensor portion 10 comprises two static electrodes and an electrostatically driven membrane between them.

It is to be understood that the disclosed embodiments of the invention are not limited to the specific structures, process steps, or materials disclosed herein, but extend to equivalents thereof as will be recognized by those skilled in the relevant art. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

Reference in the specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Where a numerical value is referred to using a term such as about or substantially, the exact numerical value is also disclosed.

As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a public list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no single member of such list should be construed as an equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and examples of the present invention may be referred to herein along with alternatives for the various components thereof. It should be understood that such embodiments, examples, and alternatives are not to be construed as actual equivalents to each other, but are to be considered as independent and autonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the previous description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention may be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

While the foregoing examples illustrate the principles of the invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and implementation details are possible. Without the exercise of inventive faculty and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

The verbs "comprise" and "comprise" are used herein as open-ended limitations that neither exclude nor require the presence of unrecited features. The features recited in the dependent claims may be freely combined with each other, unless explicitly stated otherwise. Furthermore, it should be understood that the use of "a" or "an" (i.e., singular forms) throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

At least some embodiments of the invention find industrial application in pressure sensors.

Abbreviation list

ASIC specific integrated circuit

DRIE deep reactive ion etching

FPGA field programmable gate array

HVAC heating, ventilating and air conditioning system

MEMS micro-electro-mechanical system