Resonant pressure sensor with adjustable measuring range and sensitivity

Abstract

The invention provides a resonant pressure sensor with adjustable measuring range and sensitivity, and relates to the technical field of sensors, and the resonant pressure sensor comprises a pressure sensitive film which is used for detecting external pressure; the resonator layer comprises a double-end clamped resonant beam, the double-end clamped resonant beam is arranged above the pressure sensitive film, a movable part of the double-end clamped resonant beam is suspended, one side of the double-end clamped resonant beam is provided with two driving electrodes for applying an alternating current driving signal and a parameter pumping alternating current signal respectively, and the other side of the double-end clamped resonant beam is provided with two detection electrodes; the silicon sealing cover layer is provided with a resonant cavity, and the resonant cavity is located above the pressure sensitive film and the double-end clamped resonant beam and used for providing a deformation space for the pressure sensitive film and providing a vibration space for the double-end clamped resonant beam; in the first working mode, the first-order mode of the resonant beam is split into two amplitude peak values by applying a parameter pumping alternating current signal, and the sensitivity of the output amplitude ratio is adjusted by adjusting the amplitude of the parameter pumping alternating current signal; the measurement range is adjusted by adjusting the frequency of the parameter pumping alternating current signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, and more particularly, to a resonant pressure sensor with adjustable range sensitivity. BACKGROUND

[0002] Resonant MEMS pressure sensors are widely used in aerospace, industrial control, meteorological monitoring and other fields due to their small size, digital output, good stability and high comprehensive precision. However, due to the limitations of process and design principles, the actual devices often have low sensitivity and poor resolution, which limits their further development and application. In order to realize high-performance resonant pressure sensors and ensure their high stability and resolution, the sensitivity of the sensor needs to be improved.

[0003] Currently, the main methods to improve the sensitivity of resonant MEMS pressure sensors include optimizing sensor size parameters, using high-order mode sensing, and using weakly coupled resonator amplitude ratio output. In terms of optimizing sensor size parameters, the sensitivity of the pressure sensor is effectively improved by reducing the size of the resonator, increasing the area of the pressure sensitive membrane, and reducing the thickness of the membrane, but at the same time, the effective range of the sensor is reduced and the process difficulty is increased. Using high-order mode sensing is limited by the low signal-to-noise ratio, which affects the noise level and comprehensive performance of the sensor. Using weakly coupled resonators and utilizing amplitude ratio output greatly improves the sensitivity and resolution of the sensor, but it completely discards the precision advantage of the resonant frequency output, resulting in low comprehensive precision. Therefore, it is necessary to explore new methods to improve sensitivity without affecting the original detection performance of the sensor, to further improve the sensitivity of resonant pressure sensors and achieve higher performance resonant MEMS pressure sensors.

[0004] In recent years, parameter pumping of MEMS resonators has been widely studied, which can be used to manipulate the vibration mode of the resonator and modulate the characteristics of the resonator. By applying an additional excitation signal with a fixed amplitude and frequency to the MEMS resonator, the fixed excitation signal is called parameter pumping. Parameter pumping provides a controllable and easy-to-implement approach to achieve intermodal parametric coupling, which can greatly improve the sensitivity of the sensor and thus improve the resolution of the sensor. The sensitivity improvement method based on parameter pumping does not require or affect the structure size of the sensitive beam of the sensor, and is expected to improve the sensitivity of the resonant pressure sensor without affecting the original detection performance of the sensor, to achieve higher performance indicators. SUMMARY

[0005] Therefore, the present application provides a resonant pressure sensor with adjustable range sensitivity, which solves the problems of low sensitivity and insufficient resolution of traditional resonant pressure sensors.

[0006] One aspect of the present application provides a resonant pressure sensor with adjustable range sensitivity, comprising: a pressure sensitive membrane layer, comprising a pressure sensitive membrane for detecting external pressure; a resonator layer, comprising a resonator beam, the resonator beam is arranged above the pressure sensitive membrane and its movable part is suspended, one side is provided with two driving electrodes for applying AC driving signal and parameter pumping AC signal respectively, and the other side is provided with two detection electrodes; a packaging layer, comprising a silicon cover layer, the silicon cover layer has a resonant cavity above the pressure sensitive membrane and the resonator beam, for providing deformation space for the pressure sensitive membrane and vibration space for the resonator beam; wherein, in a first working mode, the first order mode of the resonator beam is split into two amplitude peaks by applying the parameter pumping AC signal, the amplitude ratio sensitivity is adjusted by adjusting the amplitude of the parameter pumping AC signal; the measurement range is adjusted by adjusting the frequency of the parameter pumping AC signal.

[0007] According to an embodiment of the present application, in the first working mode, the frequency of the parameter pumping AC signal is the frequency difference between the first order mode and the second order mode of the resonator beam.

[0008] According to an embodiment of the present application, in a second working mode, the parameter pumping AC signal is not input; when the external pressure changes, the resonant frequency of the resonator beam is detected based on the detection electrodes on the opposite side of the driving electrodes applying the AC driving signal, and the pressure value of the external pressure is calculated based on the change amount of the resonant frequency.

[0009] According to an embodiment of the present application, the pressure sensitive membrane layer further comprises: an insulating layer arranged at the edge area of the upper surface of the pressure sensitive membrane, for isolating the pressure sensitive membrane layer from the resonator layer.

[0010] According to an embodiment of the present application, the packaging layer further comprises: an oxidation layer arranged between the silicon cover layer and the resonator layer, for insulating the silicon cover layer from the resonator layer.

[0011] According to an embodiment of the present application, an electrical isolation layer is arranged around the electrodes of the resonator layer, the electrical isolation layer is used to isolate the electrodes, and the electrodes at least include the two driving electrodes and the two detection electrodes.

[0012] According to an embodiment of the present application, a plurality of through holes are vertically arranged at the bottom of the pressure sensitive membrane layer, the through holes pass through the insulating layer and communicate with the electrodes of the resonator layer, for providing a channel for external lead wires.

[0013] The packaging layer further comprises: a metal layer arranged between the oxidation layer and the oxidation layer, for bonding the resonator layer and the packaging layer.

[0014] According to the embodiment of the present application, the resonant cavity top is covered with a getter.

[0015] According to the embodiment of the present application, the resonant pressure sensor with adjustable range sensitivity applies an additional parameter pumping AC signal to the resonant beam, and when the external pressure changes slightly, the response to the external pressure is obtained by detecting the amplitude ratio of the two peaks obtained by splitting the first mode of the resonant beam. The relative sensitivity of the amplitude ratio to the external pressure is generally more than one thousand times the relative sensitivity of the resonant frequency to the pressure, which can effectively improve the sensitivity and resolution of the sensor. BRIEF DESCRIPTION OF DRAWINGS

[0016] The above and other objects, features and advantages of the present application will become more apparent from the following description of the embodiments of the present application taken with reference to the accompanying drawings, in which:

[0017] Figure 1 The structural diagram of the resonant pressure sensor with adjustable range sensitivity according to the embodiment of the present application is schematically shown;

[0018] Figure 2 The cross-sectional view of the resonant pressure sensor with adjustable range sensitivity according to the embodiment of the present application is schematically shown;

[0019] Figure 3 The diagram showing the resonant frequency of the resonant beam varying with pressure in the second working mode according to the embodiment of the present application is schematically shown;

[0020] Figure 4 The mode splitting diagram in the first working mode according to the embodiment of the present application is schematically shown;

[0021] Figure 5 The diagram showing the amplitude variation under pressure disturbance according to the embodiment of the present application is schematically shown;

[0022] Figure 6 The diagram showing the response of the amplitude ratio to pressure according to the embodiment of the present application is schematically shown.

[0023] REFERENCE SIGNS:

[0024] 1-resonator layer;

[0025] 2-pressure sensitive membrane layer;

[0026] 3-encapsulation layer;

[0027] 1-1-resonant beam;

[0028] 1-2-one driving electrode;

[0029] 1-3-the other driving electrode;

[0030] 1-4 - one detection electrode;

[0031] 1-5 - another detection electrode;

[0032] 1-6 - an electrically isolating layer;

[0033] 2-1 - a pressure sensitive membrane;

[0034] 2-2 - an insulating layer;

[0035] 2-3 - a through hole;

[0036] 3-1 - a silicon capping layer;

[0037] 3-2 - a resonant cavity;

[0038] 3-3 - a getter;

[0039] 3-4 - an oxide layer;

[0040] 3-5 - a metal layer. DETAILED DESCRIPTION

[0041] Hereinafter, embodiments of the present application will be described with reference to the accompanying drawings. It is to be understood, however, that the description is merely illustrative of the present application and in no way limits the scope of the present application. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the present application. However, it will be apparent to one skilled in the art that one or more embodiments of the present application can be practiced without these specific details. In other instances, well-known structures and

[0042] The terms used herein are merely used to describe specific embodiments and are not intended to limit the present application. The terms "include" and "have" and the like used herein indicate the presence of the described features, steps, operations, and / or components but do not preclude the presence or addition of one or more other features, steps, operations, or components.

[0043] All terms used herein, including technical and scientific terms, have the same meanings as those generally understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having meanings consistent with the context of the present description, and should not be interpreted in an idealized or overly formal way.

[0044] In the case where expressions such as "at least one of A, B, and C, etc." are used, it is generally construed that the meaning of the expression is understood by one of ordinary skill in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, a system having B alone, a system having C alone, a system having both A and B, a system having both A and C, a system having both B and C, and / or a system having A, B, and C, etc.).

[0045] As Figure 1 and Figure 2 shown, the application provides a resonant pressure sensor with adjustable range sensitivity, including a pressure sensitive membrane layer 2, a resonator layer 1 and a packaging layer 3.

[0046] In the embodiment of the application, the pressure sensitive membrane layer 2 includes a pressure sensitive membrane 2-1, and the square film area of the pressure sensitive membrane 2-1 is used for deformation under pressure to detect external pressure. The resonator layer 1 includes a double-end fixed resonant beam 1-1, which is arranged above the pressure sensitive membrane 2-1 and has a movable part suspended in the air. One side is provided with two driving electrodes (1-2 and 1-3) respectively for applying an alternating driving signal v ac and a parametric pump alternating signal v p , and the other side is provided with two detection electrodes (1-4 and 1-5). The two driving electrodes 1-2, 1-3 are respectively used for applying a normal alternating driving signal v ac and a parametric pump alternating signal v p , and the two electrodes 1-4, 1-5 are used for detecting the signal of the resonant beam 1-1. The packaging layer 3 includes a silicon cover layer 3-1, which has a resonant cavity 3-2 located above the pressure sensitive membrane 2-1 and the resonant beam 1-1, used for providing a deformation space for the pressure sensitive membrane 2-1 and a vibration space for the resonant beam 1-1. The top of the resonant cavity 3-2 is covered with a getter 3-3.

[0047] The pressure sensitive membrane layer 2 further includes an insulating layer 2-2 arranged at the edge area of the upper surface of the pressure sensitive membrane 2-1, used for isolating the pressure sensitive membrane layer 2 from the resonator layer 1 and making the movable part of the resonant beam 1-1 suspended in the air.

[0048] The packaging layer 3 further includes an oxidation layer 3-4 arranged between the silicon cover layer 3-1 and the resonator layer 1, used for insulating the silicon cover layer 3-1 from the resonator layer 1.

[0049] The packaging layer 3 further includes a metal layer 3-5 arranged between the resonator layer 1 and the oxidation layer 3-4, used as an intermediate layer for bonding the oxidation layer 3-4 and the resonator layer 1. The metal layer 3-5 can not exist, depending on the bonding method, which is not limited to eutectic bonding, silicon-silicon direct bonding, etc.

[0050] An electrical isolation layer 1-6 is arranged around the electrodes of the resonator layer 1, which is used to isolate the electrodes, and the electrodes at least include two driving electrodes 1-2, 1-3 and two detection electrodes 1-4, 1-5.

[0051] According to the embodiment of the application, a plurality of through holes 2-3 are vertically arranged at the bottom of the pressure sensitive membrane layer, which pass through the insulating layer 2-2 and communicate with the electrodes of the resonator layer 1, used for providing a channel for external leads.

[0052] In the embodiments of the present application, the measurement range and sensitivity of pressure detection by the two detection electrodes are adjusted by adjusting the amplitude and frequency of the parameter pump alternating current signal v p .

[0053] Specifically, the range and sensitivity adjustable resonant pressure sensor has two working modes. The first working mode of the range and sensitivity adjustable resonant pressure sensor is a high sensitivity mode, and the second working mode is a normal mode.

[0054] In the second working mode, i.e. the normal mode, no parameter pump alternating current signal v p is input to the range and sensitivity adjustable resonant pressure sensor, and as the external pressure changes by ΔP, the first-order modal resonance frequency of the resonant beam 1-1 changes by Δf. The resonant beam 1-1 is driven by the driving electrode 1-2 on one side of the resonant beam 1-1, and the detection electrode 1-4 on the other side detects the resonance frequency of the resonant beam 1-1. The mapping of the resonance frequency of the resonant beam 1-1 with the change of the external pressure can be obtained, and thus the pressure value is calculated, such as Figure 3 . In this case, the sensitivity and resolution of the sensor are limited.

[0055] In the first working mode, i.e. the high sensitivity mode, a parameter pump alternating current signal v p is needed to be applied to the resonant beam 1-1 by the driving electrode 1-3, and the frequency fp is the difference between the first-order modal and second-order modal frequencies of the resonant beam 1-1, i.e. f2-f1, so that the first-order modal of the resonant beam 1-1 is split, such as Figure 4 . When the external pressure changes slightly, the two peaks I-1 and I-2 obtained by splitting the first-order modal of the resonant beam 1-1 exhibit a similar modal localization phenomenon, and the amplitude values of the two peaks change greatly, such as Figure 5 . By measuring the amplitude ratio AR of the two peaks by the detection electrodes 1-4 / 1-5, the pressure value of the external pressure can be calculated based on the amplitude ratio of the two amplitude peaks, such as Figure 6 . The relative sensitivity of the amplitude ratio of the two peaks I-1 and I-2 to the external pressure is generally more than one thousand times the relative sensitivity of the resonance frequency of the resonant beam 1-1 to the pressure, which can effectively improve the sensitivity and resolution of the sensor.

[0056] According to the above embodiments, the sensitivity of the output amplitude ratio is adjusted by adjusting the amplitude of the parameter pump alternating current signal v p , and the measurement range is adjusted by adjusting the frequency of the parameter pump alternating current signal v p .

[0057] Specifically, the amplitude ratio of the two peaks I-1 and I-2 is adjustable to the pressure. By increasing / decreasing the amplitude V p of the parametric pumping AC signal v p applied to the driving electrode 1-3, the modal coupling and modal splitting are enhanced / attenuated, and thus the amplitude ratio sensitivity is reduced / increased.

[0058] When the amplitude of the parametric pumping AC signal v p applied to the driving electrode 1-3 is fixed, the measurement range of the high-sensitivity mode is limited. By changing the frequency f p of the parametric pumping AC signal v p , the measurement range of the high-sensitivity mode can be adjusted, so that high-sensitivity and high-resolution pressure measurement can be achieved in the full-range of the resonant pressure sensor.

[0059] Briefly, in the full range, the amplitude ratio output formula of the high-sensitivity mode can be summarized as:

[0060]

[0061] wherein, P is the external pressure, is the measurement range of the high-sensitivity mode after the amplitude of the parametric pumping AC signal v p is determined, is the sensitivity coefficient related to the amplitude V p of the parametric pumping AC signal and the modal coupling strength, is the high-sensitivity mode pressure reference point related to the frequency f p of the parametric pumping AC signal. By changing the amplitude V p of the parametric pumping AC signal, the sensitivity of the high-sensitivity mode amplitude ratio output can be adjusted; by changing the frequency f p of the parametric pumping AC signal, the high-sensitivity mode pressure reference point can be adjusted, and thus the measurement range of the high-sensitivity mode is adjusted, so that the resonant pressure sensor achieves full-range adjustable sensitivity measurement.

[0062] The resonant pressure sensor with adjustable range sensitivity provided by the embodiments has two measurement modes. By additionally applying a parametric pumping AC signal v p to the resonant beam 1-1, when a small change occurs in the external pressure, the amplitude ratio of the two peaks I-1 and I-2 obtained by detecting the first-order modal splitting of the resonant beam 1-1 is used to obtain the response to the external pressure. The relative sensitivity of the amplitude ratio to the external pressure is generally more than one thousand times the relative sensitivity of the resonant frequency to the pressure, which can effectively improve the sensitivity and resolution of the sensor.

[0063] By adjusting the parametric pumping AC signal v pthe amplitude of the pump AC signal v p the frequency of the pump AC signal v

[0064] The above-described embodiments of the present application are merely descriptive and are not intended to limit the scope of the present application. Although the respective embodiments are described above, this does not mean that the measures in the respective embodiments cannot be advantageously used in combination. Various alternatives and modifications to the embodiments described herein will be apparent to those skilled in the art in view of the foregoing description. Such alternatives and modifications are intended to fall within the scope of the application.

Claims

1. A resonant pressure sensor with adjustable range sensitivity, characterized in that: include: A pressure-sensitive membrane layer (2), comprising a pressure-sensitive membrane (2-1), wherein the pressure-sensitive membrane (2-1) is used to detect external pressure; The resonator layer (1) comprises a resonant beam (1-1), wherein the resonant beam (1-1) is arranged above the pressure sensitive film (2-1) and its movable portion is suspended in the air, and one side is provided with two driving electrodes for applying an AC driving signal and a parameter pumping AC signal respectively, and the other side is provided with two detection electrodes for detecting the vibration of the resonant beam (1-1); The packaging layer (3) comprises a silicon capping layer (3-1), wherein the silicon capping layer (3-1) has a resonant cavity (3-2), and the resonant cavity (3-2) is located above the pressure sensitive film (2-1) and the resonant beam (1-1), and is used to provide a deformation space for the pressure sensitive film (2-1) and a vibration space for the resonant beam (1-1); In the first working mode, the first-order mode of the resonant beam (1-1) is split into two amplitude peaks by applying the parameter pumping AC signal, and the sensitivity of the output amplitude ratio is adjusted by adjusting the amplitude of the parameter pumping AC signal; and the measurement range is adjusted by adjusting the frequency of the parameter pumping AC signal.

2. The resonant pressure sensor with adjustable range sensitivity according to claim 1, characterized in that: In the first working mode, the frequency of the parametric pumping AC signal is the frequency difference between the first-order mode and the second-order mode of the resonant beam (1-1).

3. The resonant pressure sensor with adjustable range sensitivity according to claim 1, characterized in that: In the second working mode, the parameter pumping AC signal is not input; When the external pressure changes, the resonance frequency of the resonance beam (1-1) is detected based on the detection electrode on the opposite side of the driving electrode applying the AC driving signal, and the pressure value of the external pressure is calculated based on the change in the resonance frequency.

4. The resonant pressure sensor with adjustable range sensitivity according to claim 1, characterized in that: The pressure sensitive film layer (2) further comprises: An insulating layer (2-2) is provided in an edge region of the upper surface of the pressure sensitive membrane and is used to isolate the pressure sensitive membrane layer (2) from the resonator layer (1).

5. The resonant pressure sensor with adjustable range sensitivity according to claim 1, characterized in that: The encapsulation layer (3) further comprises: An oxide layer (3-4) is provided between the silicon capping layer (3-1) and the resonator layer (1) and is used to insulate the silicon capping layer (3-1) from the resonator layer (1).

6. The resonant pressure sensor with adjustable range sensitivity according to claim 1, characterized in that: An electrical isolation layer (1-6) is provided around the electrodes of the resonator layer (1), and the electrical isolation layer (1-6) is used to isolate the electrodes, and the electrodes at least include the two driving electrodes and the two detection electrodes.

7. The resonant pressure sensor with adjustable range sensitivity according to claim 6, characterized in that: A plurality of through holes (2-3) are vertically provided at the bottom of the pressure-sensitive membrane layer (2); the through holes (2-3) are connected to the electrodes of the resonator layer (1) and are used to provide channels for external leads.

8. The resonant pressure sensor with adjustable range sensitivity according to claim 1, characterized in that: The top of the resonant cavity (3-2) is covered with a getter (3-3).

9. The resonant pressure sensor with adjustable range sensitivity according to claim 5, characterized in that: Also includes: A metal layer (3-5) is used to bond the oxide layer (3-4) to the resonator layer (1).

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