MEMS accelerometer based on piezoresistance-avalanche effect
By setting an effect junction in the beam stress change area of the MEMS accelerometer, combining the reverse bias power supply and the measurement module, high sensitivity and high accuracy acceleration measurement are achieved, and the problems of complex structure, large volume and high cost in the prior art are solved.
Patent Information
- Application Number
- CN202422435505.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-09
- Publication Date
- 2025-08-08
- Estimated Expiration
- 2034-10-09
AI Technical Summary
Existing MEMS accelerometers have shortcomings in measurement sensitivity, structural complexity, manufacturing cost and volume, and it is difficult to meet the needs of high sensitivity, simple structure, low cost and small volume at the same time.
Using a MEMS accelerometer based on piezoresistive-avalanche effect, the effect junction is set in the stress change area of the beam body, and the reverse bias power supply and measurement module are connected, and the high-precision measurement of acceleration is used to measure the breakdown electrical parameters of the effect junction, and the precise calculation of acceleration is performed in combination with the control module.
It improves the measurement sensitivity and accuracy of the accelerometer, has a simple structure, small size, low manufacturing difficulty and low cost.
Smart Images
Figure CN223205495U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of micro-electromechanical sensors, in particular to a MEMS accelerometer based on piezoresistive-avalanche effect. Background Art
[0002] MEMS (Micro-Electro-Mechanical System) accelerometers are widely used for acceleration measurement, primarily including capacitive, piezoresistive, and piezoelectric accelerometers. Capacitive accelerometers have high manufacturing process requirements and poor measurement sensitivity; piezoresistive accelerometers have low measurement sensitivity, complex structures, and large size; and piezoelectric accelerometers are difficult and expensive to manufacture. Therefore, there is an urgent need for an accelerometer that simultaneously meets the requirements of high measurement sensitivity, simple structure, low manufacturing cost, and compact size. Utility Model Content
[0003] The purpose of the utility model is to provide a MEMS accelerometer based on piezoresistive-avalanche effect, so as to meet the requirements of high measurement sensitivity, simple structure, low manufacturing cost and compact size.
[0004] To achieve the above effects, the present invention provides a MEMS accelerometer based on the piezoresistive-avalanche effect, comprising a base and a beam disposed on the base, wherein the beam has a stress change region and the stress change region is provided with an effect junction having the piezoresistive-avalanche effect:
[0005] The accelerometer also includes a reverse bias power supply and a measurement module, both of which are connected to both ends of the effect junction, wherein the reverse bias power supply is used to apply a reverse voltage to the effect junction to cause it to enter a breakdown state, and the measurement module is used to measure the breakdown electrical parameters of the effect junction, and the reverse bias power supply and the measurement module are both communicatively connected to the control module.
[0006] Optionally, the reverse bias power supply is a reverse bias voltage source with a constant voltage, the measuring module is used to measure the breakdown current of the effector junction, and the control module determines the acceleration according to the following formula:
[0007]
[0008] in,
[0009] V Th =k B T / q;
[0010] Where a in is the acceleration of the accelerometer, m / s 2; △I is the breakdown current change of the effect junction when the accelerometer is subjected to acceleration, A; α is the material parameter of the beam body related to the energy band gap, eV / Pa; E is the Young's modulus, GPa; q is the electron charge constant, 1.602×10 -19 C; V Th is the thermal voltage, V; V BR0 is the reverse constant voltage applied by the reverse bias voltage source to the effect junction, V; I0 is the initial breakdown current of the effect junction when the accelerometer is not subjected to acceleration, A; n is the error coefficient; h is the thickness of the beam, m; L is the length of the beam, m; M eff is the equivalent movable mass of the accelerometer, kg; K eff is the equivalent stiffness of the accelerometer, N / m; k B is the Boltzmann constant; T is the absolute temperature of the environment in which the beam is located, K.
[0011] Optionally, the reverse bias power supply is a reverse bias current source with a constant current, the measuring module is used to measure the breakdown voltage of the effector junction, and the control module determines the acceleration according to the following formula:
[0012]
[0013] Where a in is the acceleration of the accelerometer, m / s 2 ; △V BR is the breakdown voltage change of the effect junction when the accelerometer is subjected to acceleration, V; α is the material parameter of the beam body related to the energy band gap, eV / Pa; E is the Young's modulus, GPa; V BR0 is the initial breakdown voltage of the effect junction when the accelerometer is not subjected to acceleration, V; E g0 The initial band gap of the material used for the beam, eV; k B is the Boltzmann constant; T is the absolute temperature of the environment where the beam is located, K; h is the thickness of the beam, m; L is the length of the beam, m; M eff is the equivalent movable mass of the accelerometer, kg; K eff is the equivalent stiffness of the accelerometer, N / m.
[0014] Optionally, the effective junction is a PN junction.
[0015] Optionally, the beam body is connected to the base through an anchor area, and a connection area between the beam body and the anchor area serves as the stress change area.
[0016] Optionally, the anchor area is provided with a first electrode and a second electrode, the first electrode is connected to the first end of the effect junction, and the second electrode is connected to the second end of the effect junction; the two power supply ends of the reverse bias power supply are connected to the first electrode and the second electrode one by one, and the two connection ends of the measurement module are connected to the first electrode and the second electrode one by one.
[0017] Optionally, the beam body is a cantilever beam, and a mass block is provided at the suspended end of the beam body.
[0018] Optionally, the measurement module includes an amplifier.
[0019] Optionally, the circuit formed by the effector junction and the reverse bias power supply is provided with an amplifier circuit.
[0020] The MEMS accelerometer provided by the present invention can, based on the piezoresistive-avalanche effect of the effect junction, amplify and display the stress change in the stress change zone through the initial breakdown electrical parameter and the breakdown electrical parameter change value with a large change amplitude, so as to improve the sensing sensitivity of the accelerometer to the acceleration. At the same time, the acceleration, structural related parameters, the stress in the stress change zone, the initial breakdown electrical parameter and the breakdown electrical parameter change value are comprehensively considered to more accurately obtain the acceleration, thereby greatly improving the measurement sensitivity of the accelerometer. At the same time, the MEMS accelerometer only needs to set a simple effect junction in the stress change zone of its beam body and connect it to a reverse bias power supply, and then cooperate with the measurement module and the control module to perform high-precision acceleration measurement. The structure is simple, the size is compact, the manufacturing difficulty is low, and the cost is low. BRIEF DESCRIPTION OF THE DRAWINGS
[0021] In order to more clearly illustrate the specific implementation methods of the utility model or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.
[0022] Figure 1 A top view of a MEMS accelerometer based on piezoresistive-avalanche effect provided by an embodiment of the present invention in a first form;
[0023] Figure 2 A front cross-sectional view of a MEMS accelerometer based on piezoresistive-avalanche effect provided by an embodiment of the present invention in a first form;
[0024] Figure 3 A top view of the MEMS accelerometer based on the piezoresistive-avalanche effect provided by an embodiment of the present invention in the second form;
[0025] Figure 4 A schematic flow chart of a measurement method for a MEMS accelerometer based on piezoresistive-avalanche effect provided in an embodiment of the present invention.
[0026] Description of reference numerals:
[0027] 100 - beam body; 200 - effector junction; 300 - anchor region; 410 - first electrode; 420 - second electrode; 500 - mass block. DETAILED DESCRIPTION
[0028] The following is a clear and complete description of the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.
[0029] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended solely to facilitate the description of this utility model and simplify the description. They do not indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0030] In the description of this utility model, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections, electrical connections; direct connections, indirect connections through an intermediate medium, and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.
[0031] This embodiment provides a MEMS accelerometer based on piezoresistive-avalanche effect, such as Figure 1 and Figure 2As shown, it includes a base and a beam body 100 arranged on the base, the beam body has a stress change zone and the stress change zone is provided with an effect junction 200 with a piezoresistive-avalanche effect: the accelerometer also includes a reverse bias power supply and a measurement module both connected to both ends of the effect junction 200, wherein the reverse bias power supply is used to apply a reverse voltage to the effect junction 200 to make it enter a breakdown state, and the measurement module is used to measure the breakdown electrical parameters of the effect junction 200, and the reverse bias power supply and the measurement module are both communicatively connected to the control module.
[0032] When using the above-mentioned MEMS accelerometer for measurement, if Figure 4 As shown, the measurement method may specifically include:
[0033] S402 adjusts the reverse bias power supply to apply a reverse voltage to the effect junction to put the effect junction into a breakdown state.
[0034] During use, the reverse voltage applied to the effect junction by adjusting the reverse bias power supply causes the effect junction to enter a breakdown state. In the breakdown state, the effect junction has a piezoresistive-avalanche effect. Specifically, when the vibration source applies acceleration to the accelerometer, according to the Euler-Bernoulli beam theory, the stress change zone generates corresponding stress, which can cause the electron mobility and energy band gap at the effect junction to change, thereby causing the breakdown electrical parameters of the effect junction, such as the breakdown voltage / breakdown current, to change significantly, and the mechanical stress of the stress change zone is approximately linearly amplified, and accordingly the breakdown electrical parameters of the effect junction have a high sensitivity to the mechanical stress of the stress change zone.
[0035] The S404 measurement module detects the breakdown electrical parameters of the effector junction and feeds back the parameters to the control module.
[0036] S406 The control module determines the acceleration according to a preset formula, wherein the parameters of the preset formula include the initial breakdown electrical parameters of the effect junction before the accelerometer is subjected to acceleration, the breakdown electrical parameter change value of the effect junction when the accelerometer is subjected to acceleration, and the structural related parameters of the accelerometer.
[0037] The control module stores structural parameters related to the accelerometer's own mechanical structure, connection circuit structure, environment, etc., as well as a preset formula for calculating acceleration. The structural parameters can correlate the acceleration experienced by the accelerometer and the magnitude of the stress experienced by the stress change zone. The measurement module detects the breakdown electrical parameters of the effect junction in real time and feeds them back to the control module. The control module uses the breakdown electrical parameter fed back by the measurement module when the accelerometer is not experienced with acceleration as the initial breakdown electrical parameter, and uses the breakdown electrical parameter fed back by the measurement module when the accelerometer is experienced with acceleration and the change value of the initial breakdown electrical parameter as the breakdown electrical parameter change value. The initial breakdown electrical parameter and the breakdown electrical parameter change value with a larger change amplitude can amplify and characterize the stress magnitude of the stress change zone. Subsequently, the control module substitutes the structural parameters, the initial breakdown electrical parameter and the breakdown electrical parameter change value into the preset formula to calculate the acceleration.
[0038] The MEMS accelerometer of this embodiment can amplify and display the stress change in the stress change zone through the initial breakdown electrical parameters and the breakdown electrical parameter change value with a large change amplitude based on the piezoresistive-avalanche effect of the effect junction, so as to improve the sensing sensitivity of the accelerometer to the acceleration. At the same time, the acceleration, structural related parameters, the stress in the stress change zone, the initial breakdown electrical parameters and the breakdown electrical parameter change value are comprehensively considered to more accurately obtain the acceleration, thereby greatly improving the measurement sensitivity of the accelerometer. At the same time, the MEMS accelerometer only needs to set a simple effect junction in the stress change zone of its beam body and connect it to a reverse bias power supply, and then cooperate with the measurement module and the control module to perform high-precision acceleration measurement. It has a simple structure, a compact size, low manufacturing difficulty and low cost.
[0039] Specifically, the measurement module may include an amplifier to ensure its sensitivity and accuracy in measuring the breakdown electrical parameters of the effector junction, and accordingly ensure the sensitivity and accuracy of the accelerometer in measuring acceleration. Specifically, the amplifier may be a lock-in amplifier.
[0040] Specifically, the reverse bias power supply may be a reverse bias voltage source with a constant voltage, the measuring module is used to measure the breakdown current of the effector junction, and the control module determines the acceleration according to the following formula:
[0041]
[0042] in,
[0043] V Th =k B T / q;
[0044] Where a in is the acceleration of the accelerometer, m / s 2; △I is the change in breakdown current of the accelerometer junction when it is subjected to acceleration, A; α is the material parameter related to the beam body and the energy band gap, eV / Pa; E is the Young's modulus, GPa; q is the electron charge constant, 1.602×10 -19 C; V Th is the thermal voltage, V; V BR0 is the reverse constant voltage applied by the reverse bias voltage source to the effect junction, V; I0 is the initial breakdown current of the effect junction when the accelerometer is not subjected to acceleration, A; n is the error coefficient; h is the thickness of the beam, m; L is the length of the beam, m; M eff is the equivalent movable mass of the accelerometer, kg; K eff is the equivalent stiffness of the accelerometer, N / m; k B is the Boltzmann constant; T is the absolute temperature of the environment in which the beam is located, K.
[0045] Among them, a in is the acceleration measured by the accelerometer; △I is the breakdown current change value, i.e., the breakdown electrical parameter change value; I0 is the initial breakdown current, i.e., the initial breakdown electrical parameter; α, E, q, V Th 、V BR0 , n, k B ,T,h,L,M eff , K eff is the structural parameter related to the micromechanical structure itself, the connection circuit structure, the environment, etc. According to the above formula, the known quantitative parameters and the measured variable parameters, the acceleration a can be accurately measured. in .
[0046] In addition to the reverse bias voltage source described above, in this embodiment, the reverse bias power supply may also be a reverse bias current source with a constant current. The measurement module is used to measure the breakdown voltage of the effector junction, and the control module determines the acceleration according to the following formula:
[0047]
[0048] Where a in is the acceleration of the accelerometer, m / s 2 ; △V BR is the breakdown voltage change of the accelerometer when it is subjected to acceleration, V; α is the material parameter related to the beam body and the energy band gap, eV / Pa; E is the Young's modulus, GPa; V BR0 is the initial breakdown voltage of the accelerometer when it is not subjected to acceleration, V; E g0 is the initial energy band gap of the material used for the beam, eV; k B is the Boltzmann constant; T is the absolute temperature of the environment where the beam is located, K; h is the thickness of the beam, m; L is the length of the beam, m; M effis the equivalent movable mass of the accelerometer, kg; K eff is the equivalent stiffness of the accelerometer, N / m.
[0049] Among them, a in Acceleration measured by the accelerometer; △V BR is the breakdown voltage change value, i.e. the breakdown electrical parameter change value; V BR0 is the initial breakdown voltage, i.e. the initial breakdown electrical parameter; α, E g0 、k B ,T,E,h,L,M eff , K eff are structural parameters related to the accelerometer's own structure, connection circuit structure, and environment. Based on the above formula, known quantitative parameters, and measured variable parameters, the acceleration a can be accurately measured. in .
[0050] Specifically, in this embodiment, the effect junction 200 may be a PN junction. During manufacturing, a lightly doped PN junction may be obtained at the beam body through a doping process.
[0051] Optionally, in this embodiment, if Figure 1-Figure 3 As shown, the beam is connected to the base via an anchor region 300, with the connection between the beam 100 and the anchor region 300 serving as a stress variation zone. When the accelerometer is subjected to the same acceleration, the stress induced in the connection between the beam 100 and the anchor region 300 varies significantly, triggering a greater degree of piezoresistance-avalanche effect in the effector junction. Consequently, the magnitude of the change in the breakdown electrical parameters of the effector junction 200 increases, further enhancing the stress and acceleration amplification in the stress variation zone, thereby further improving the accelerometer's measurement sensitivity.
[0052] Of course, in some other embodiments, the effect junction may also be set in any other area of the beam body 100 that can sense stress changes.
[0053] Specifically, in this embodiment, Figure 3 As shown, a first electrode 410 and a second electrode 420 can be disposed in the anchor region 300. The first electrode 410 is connected to the first end of the effect junction, and the second electrode 420 is connected to the second end of the effect junction. The two power supply terminals of the reverse bias power supply are connected to the first electrode 410 and the second electrode 420 in a one-to-one correspondence, and the two connection terminals of the measurement module are connected to the first electrode 410 and the second electrode 420 in a one-to-one correspondence. The effect junction is relatively small. The first and second electrodes, which are relatively large and fixed in position, are disposed in the anchor region. When connected, the reverse bias power supply and the measurement module can achieve connection with the effect junction through connection with the first and second electrodes, thereby improving connection convenience and connection stability, and correspondingly improving the manufacturing convenience and operational stability of the accelerometer.
[0054] Specifically, in this embodiment, Figure 1 As shown, beam 100 is a cantilever beam, with a mass 500 attached to the suspended end of beam 100. When the accelerometer is subjected to acceleration, the beam, with one end suspended and connected to mass 500, experiences stronger elastic vibration and greater induced stress changes. This enhances the triggering of the piezoresistance-avalanche effect of the effector junction, further improving the effect of the effector junction's breakdown electrical parameters on the stress in the stress change region and the amplification of acceleration, thereby further improving the accelerometer's measurement sensitivity.
[0055] Of course, in some other embodiments, the beam body can also be a fixed beam with both ends fixed or a membrane beam with a smaller thickness. At the same time, the beam body can be in the form of a single beam, a double beam or multiple beams.
[0056] In this embodiment, an amplifier circuit may be provided in the circuit formed by the effect junction and the reverse bias power supply. When in use, the amplifier circuit can amplify the amplitude of the change in the breakdown electrical parameter of the effect junction, thereby further enhancing the amplification effect of the effect junction on the stress and acceleration in the stress change region, and correspondingly further improving the measurement sensitivity and accuracy of the accelerometer.
[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A MEMS accelerometer based on piezoresistive-avalanche effect, characterized in that: The invention comprises a base and a beam body (100) arranged on the base, wherein the beam body has a stress change region and the stress change region is provided with an effect junction (200) having a piezoresistive-avalanche effect: The accelerometer further comprises a reverse bias power supply and a measurement module both connected to both ends of the effect junction (200), wherein the reverse bias power supply is used to apply a reverse voltage to the effect junction (200) to cause it to enter a breakdown state, and the measurement module is used to measure the breakdown electrical parameters of the effect junction, and the reverse bias power supply and the measurement module are both communicatively connected to a control module.
2. The MEMS accelerometer according to claim 1, wherein: The reverse bias power supply is a reverse bias voltage source with a constant voltage. The measuring module is used to measure the breakdown current of the effect junction. The control module determines the acceleration according to the following formula: in, VTh=kBT / q Where a in is the acceleration of the accelerometer, m / s 2 ; △I is the breakdown current change of the effect junction when the accelerometer is subjected to acceleration, A; α is the material parameter of the beam body related to the energy band gap, eV / Pa; E is the Young's modulus, GPa; q is the electron charge constant, 1.602×10- 19 C; V Th is the thermal voltage, V; V BR0 is the reverse constant voltage applied by the reverse bias voltage source to the effect junction (200), V; I0 is the initial breakdown current of the effect junction (200) when the accelerometer is not subjected to acceleration, A; n is the error coefficient; h is the thickness of the beam, m; L is the length of the beam, m; Mef f is the equivalent movable mass of the accelerometer, kg; Kef f is the equivalent stiffness of the accelerometer, N / m; k B is the Boltzmann constant; T is the absolute temperature of the environment in which the beam (100) is located, in K.
3. The MEMS accelerometer according to claim 1, wherein: The reverse bias power supply is a reverse bias current source with a constant current, the measuring module is used to measure the breakdown voltage of the effect junction (200), and the control module determines the acceleration according to the following formula: Where a in is the acceleration of the accelerometer, m / s 2 ; △V BR is the breakdown voltage change of the effect junction when the accelerometer is subjected to acceleration, V; α is the material parameter of the beam body related to the energy band gap, eV / Pa; E is the Young's modulus, GPa; V BR0 is the initial breakdown voltage of the effect junction when the accelerometer is not subjected to acceleration, V; E g0 The initial band gap of the material used for the beam, eV; k B is the Boltzmann constant; T is the absolute temperature of the environment where the beam is located, K; h is the thickness of the beam, m; L is the length of the beam, m; M eff is the equivalent movable mass of the accelerometer, kg; K eff is the equivalent stiffness of the accelerometer, N / m.
4. The MEMS accelerometer according to any one of claims 1 to 3, characterized in that: The effective junction is a PN junction.
5. The MEMS accelerometer according to any one of claims 1 to 3, characterized in that: The beam body is connected to the base through an anchoring area (300), and the connection area between the beam body (100) and the anchoring area (300) serves as the stress change area.
6. The MEMS accelerometer according to claim 5, wherein: The anchor region is provided with a first electrode (410) and a second electrode (420), the first electrode (410) is connected to the first end of the effect junction (200), and the second electrode (420) is connected to the second end of the effect junction (200); the two power supply ends of the reverse bias power supply are connected to the first electrode (410) and the second electrode (420) in a one-to-one correspondence, and the two connection ends of the measurement module are connected to the first electrode (410) and the second electrode (420) in a one-to-one correspondence.
7. The MEMS accelerometer according to any one of claims 1 to 3, characterized in that: The beam body (100) is a cantilever beam, and a mass block (500) is provided at the suspended end of the beam body (100).
8. The MEMS accelerometer according to any one of claims 1 to 3, wherein: The measurement module includes an amplifier.
9. The MEMS accelerometer according to any one of claims 1 to 3, characterized in that: The circuit formed by the effect junction (200) and the reverse bias power supply is provided with an amplifier circuit.