Pressure sensor and preparation method thereof

Abstract

The invention discloses a pressure sensor and a preparation method thereof, and belongs to the technical field of semiconductors. The pressure sensor comprises at least one sensor unit, each sensor unit comprises a substrate and four inductive resistors, two input ends are electrically connected with the four inductive resistors to form an equivalent circuit, and under the action of pressure, the four inductive resistors can generate resistance changes, so that the resistance changes are changed. The pressure can be detected by measuring the voltage change condition of two output ends in the equivalent circuit. According to the embodiment of the invention, the four induction resistors are electrically connected to form a circuit structure for pressure calculation, so that the influence of other environmental factors on a calculation result can be avoided, and the accuracy of the calculation result is improved. Moreover, each of the four inductive resistors comprises a nanowire structure, the size is smaller, the piezoresistive coefficient is larger, the sensitivity is higher, and the pressure sensor has higher reliability in both low-temperature and high-temperature environments, so that the sensitivity and reliability of the pressure sensor can be improved.

Description

Technical Field

[0001] The present application belongs to the field of semiconductor technology, and in particular relates to a pressure sensor and a method for preparing the same. Background Art

[0002] Traditional pressure sensors are mostly based on the principles of piezoresistive effect, piezoelectric effect or capacitive effect, and are made of silicon materials. Boron doping is generally used as the piezoresistive material. The piezoresistive coefficient is small and the sensitivity is low. In low or high temperature environments, the temperature drift is too large and the sensor will fail.

[0003] How to improve the sensitivity of pressure sensors and improve the reliability of pressure sensors in high and low temperature environments has become an urgent problem to be solved in this field. Summary of the invention

[0004] The present application provides a pressure sensor and a preparation method thereof, aiming to improve the sensitivity and reliability of the pressure sensor.

[0005] In a first aspect, the present application provides a pressure sensor, comprising at least one sensor unit. The sensor unit comprises a substrate and a plurality of sensing resistors. The substrate comprises a first surface and a second surface opposite to each other, and a cavity penetrating the first surface and the second surface. The plurality of sensing resistors are arranged on the first surface, and the sensing resistors comprise a nanowire structure. The orthographic projections of the plurality of sensing resistors on the first surface are located within the range of the orthographic projections of the cavity on the first surface.

[0006] The plurality of sensing resistors include a first sensing resistor, a second sensing resistor, a third sensing resistor, and a fourth sensing resistor, and the pressure sensor further includes a first input terminal and a second input terminal, and a first output terminal and a second output terminal. The source of the first sensing resistor is electrically connected to the first input terminal, the drain of the first sensing resistor is electrically connected to the first output terminal and the source of the second sensing resistor, the drain of the second sensing resistor is electrically connected to the second input terminal and the drain of the third sensing resistor, the source of the third sensing resistor is electrically connected to the second output terminal and the drain of the fourth sensing resistor, and the source of the fourth sensing resistor is electrically connected to the first input terminal.

[0007] In some embodiments, the shape of the orthographic projection of the cavity on the first surface is a circle. The length extension direction of the first sensing resistor, the length extension direction of the second sensing resistor, the length extension direction of the third sensing resistor, and the length extension direction of the fourth sensing resistor are all the same as a diameter direction of the circle.

[0008] In some embodiments, the width of the sensing resistor ranges from 2 nm to 2000 nm.

[0009] In some embodiments, the sensing resistor further includes a gate, and the gate is disposed between the source and the drain of the sensing resistor.

[0010] In some embodiments, the nanowire structure further comprises a semiconductor layer and a barrier layer which are stacked. The material of the semiconductor layer comprises at least one of gallium nitride, gallium arsenide or indium gallium arsenide, and the material of the barrier layer comprises at least one of indium gallium nitride, aluminum gallium nitride, indium phosphide, aluminum gallium arsenide or indium aluminum arsenide.

[0011] In some embodiments, the source electrodes and drain electrodes of the plurality of sensing resistors are located in the barrier layer, and the plurality of sensing resistors are electrically connected through the barrier layer.

[0012] In some embodiments, the pressure sensor further includes a substrate disposed on the second surface.

[0013] In some embodiments, the pressure sensor further includes a packaging shell, the packaging shell includes a cavity, and the sensor unit is disposed in the cavity.

[0014] In a second aspect, the present application further provides a method for preparing a pressure sensor, comprising the following steps S10 to S20: Step S10: forming a plurality of sensing resistors on a substrate, wherein the sensing resistors include a nanowire structure.

[0015] Step S20: etching the substrate to form a cavity penetrating the substrate. The orthographic projections of the plurality of sensing resistors on the substrate are located within the region where the cavity is located.

[0016] The plurality of sensing resistors include a first sensing resistor, a second sensing resistor, a third sensing resistor and a fourth sensing resistor, and the pressure sensor further includes a first input terminal and a second input terminal, and a first output terminal and a second output terminal.

[0017] A source of the first sensing resistor is electrically connected to the first input terminal, a drain of the first sensing resistor is electrically connected to the first output terminal and the source of the second sensing resistor, a drain of the second sensing resistor is electrically connected to the second input terminal and the drain of the third sensing resistor, a source of the third sensing resistor is electrically connected to the second output terminal and the drain of the fourth sensing resistor, and a source of the fourth sensing resistor is electrically connected to the first input terminal.

[0018] In some embodiments, the step of forming a plurality of sensing resistors on a substrate includes the following steps S11 to S13: Step S11: forming a semiconductor layer on a substrate.

[0019] Step S12: forming a barrier layer on a side of the semiconductor layer away from the substrate.

[0020] Step S13: etching the barrier layer to form a plurality of source electrodes and drain electrodes of the sensing resistors and a plurality of connecting lines.

[0021] Wherein, the multiple sensing resistors are electrically connected through multiple connecting lines.

[0022] In an embodiment provided in the present application, the pressure sensor includes at least one sensor unit, and each sensor unit includes a substrate and four sensing resistors located on the substrate.

[0023] Since the substrate includes a first surface and a second surface relative to each other, and a cavity penetrating the first surface and the second surface, a plurality of sensing resistors are arranged on the first surface, and the orthographic projections of the plurality of sensing resistors on the first surface are located within the range of the orthographic projections of the cavity on the first surface, it can be understood that the four sensing resistors are in a suspended film state.

[0024] The pressure sensor also includes a first input terminal and a second input terminal, and a first output terminal and a second output terminal. Among the four sensing resistors, the source of the first sensing resistor is electrically connected to the first input terminal, the drain of the first sensing resistor is electrically connected to the first output terminal and the source of the second sensing resistor, the drain of the second sensing resistor is electrically connected to the second input terminal and the drain of the third sensing resistor, the source of the third sensing resistor is electrically connected to the second output terminal and the drain of the fourth sensing resistor, and the source of the fourth sensing resistor is electrically connected to the first input terminal. That is, the four sensing resistors are electrically connected to form a circuit structure.

[0025] When the pressure sensor is subjected to pressure, the inductive resistors in the suspended film state will each undergo a slight deformation. After the four inductive resistors are subjected to stress due to the deformation, the resistance will change under the piezoresistive effect. The magnitude of the pressure can be calculated through the differential output of the circuit. Moreover, compared with the method of measuring pressure with a single inductive resistor, the four inductive resistors are electrically connected to form a circuit structure for calculating the pressure in the embodiment of the present application, which can avoid the influence of other environmental factors on the calculation results, and is conducive to improving the accuracy of the calculation results.

[0026] In addition, all four sensing resistors include nanowire structures, which are smaller in size, more obviously deformed when subjected to stress, and have higher sensitivity. Nanowire structures usually have a larger piezoresistance coefficient, and they have a quantum confinement effect at the nanoscale, which can amplify the change in the piezoresistance effect after strain. For example, the piezoresistance coefficient of silicon nanowires is two orders of magnitude higher than that of conventional silicon, and the resistance value changes more significantly under the same force, which can make the pressure sensor have a higher sensitivity. And based on the nanowire structure, the sensing resistor works well in high and low temperature environments, which can improve the reliability of the pressure sensor.

[0027] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 A top view of a pressure sensor provided in an embodiment of the present application; Figure 2 for Figure 1 Equivalent circuit diagram of the medium-pressure sensor; Figure 3 for Figure 1 A cross-sectional view of the pressure sensor along the section line AA'; Figure 4 A top view of another pressure sensor provided in an embodiment of the present application; Figure 5 for Figure 4 A cross-sectional view of the pressure sensor along section line BB'; Figure 6 A cross-sectional view of another pressure sensor provided in an embodiment of the present application; Figure 7 A flow chart of a method for preparing a pressure sensor provided in an embodiment of the present application; Figure 8~Figure 23 A diagram of the steps for preparing a pressure sensor provided in an embodiment of the present application. DETAILED DESCRIPTION

[0029] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in some embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments provided by the present application, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present application.

[0030] Unless the context requires otherwise, throughout the specification and claims, the term "comprising" is to be construed in an open, inclusive sense, ie, meaning "including, but not limited to."

[0031] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present application, unless otherwise specified, "plurality" means two or more.

[0032] When describing some embodiments, the term "connection" and its derivative expressions may be used. The term "connection" should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For example, when describing some embodiments, the term "connection" may be used to indicate that two or more components are in direct physical or electrical contact with each other.

[0033] Additionally, the use of “based on” is meant to be open and inclusive, as a process, step, calculation, or other action “based on” one or more stated conditions or values ​​may, in practice, be based on additional conditions or values ​​beyond those stated.

[0034] It will be understood that when a layer or an element is referred to as being on another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may be present between the layer or element and the other layer or substrate.

[0035] Exemplary embodiments are described herein with reference to cross-sectional views that are idealized exemplary drawings. In the drawings, the thickness of layers and the area of ​​regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are conceivable. Therefore, the exemplary embodiments should not be interpreted as being limited to the shapes of the regions shown herein, but include deviations in shape due to, for example, manufacturing. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of the device, and are not intended to limit the scope of the exemplary embodiments.

[0036] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0037] At present, traditional pressure sensors are mostly based on the principles of piezoresistive effect, piezoelectric effect or capacitive effect, and are manufactured using silicon materials, and generally use boron doping as piezoresistive material. Due to the physical properties of the material, traditional pressure sensors have problems such as small piezoresistive coefficient and low sensitivity. In low or high temperature environments, the temperature drift is too large and the sensor will fail.

[0038] To solve the above problems, the present application provides a pressure sensor, which includes at least one sensor unit, such as Figure 1~Figure 3 As shown, Figure 1 A top view of a pressure sensor provided in an embodiment of the present application, Figure 2 for Figure 1 Equivalent circuit diagram of the pressure sensor. Figure 3 for Figure 1 A cross-sectional view of the pressure sensor along section line AA'.

[0039] Taking the pressure sensor 10 including a sensor unit as an example, the sensor unit includes a substrate 21 and a plurality of sensing resistors. The substrate 21 includes a first surface P1 and a second surface P2 opposite to each other, and a cavity K0 penetrating the first surface P1 and the second surface P2. The plurality of sensing resistors are arranged on the first surface P1, and the sensing resistors include a nanowire structure. The orthographic projections of the plurality of sensing resistors on the first surface P1 are located within the range of the orthographic projections of the cavity K0 on the first surface P1.

[0040] The plurality of sensing resistors include a first sensing resistor 201, a second sensing resistor 202, a third sensing resistor 203 and a fourth sensing resistor 204. The pressure sensor 10 further includes a first input terminal Vin and a second input terminal GND, and a first output terminal Vout. + and the second output terminal Vout - The source of the first sensing resistor 201 is electrically connected to the first input terminal Vin, and the drain of the first sensing resistor 201 is electrically connected to the first output terminal Vout. + The source of the second sensing resistor 202 is electrically connected, the drain of the second sensing resistor 202 is electrically connected to the second input terminal GND and the drain of the third sensing resistor 203, and the source of the third sensing resistor 203 is electrically connected to the second output terminal Vout. - The first sensing terminal 204 is electrically connected to the drain of the fourth sensing resistor 204 , and the source of the fourth sensing resistor 204 is electrically connected to the first input terminal Vin.

[0041] For example, Figure 2 As shown, the resistance of the first sensing resistor 201 is R1, the resistance of the second sensing resistor 202 is R2, the resistance of the third sensing resistor 203 is R3, and the resistance of the fourth sensing resistor 204 is R4. In a uniform or stationary state, that is, when no pressure is provided, the first output terminal Vout + and the second output terminal Vout - The potential difference is .

[0042] Due to the setting of the cavity K0, the four sensing resistors are in a suspended film state. Under the action of pressure, the sensing resistors will undergo slight deformation. After the four sensing resistors are subjected to stress due to the deformation, the resistance will change under the piezoresistive effect. Since the distribution of stress on the first surface P1 is not equal everywhere, the resistance change of the sensing resistors at different positions is also different.

[0043] For example, under a certain stress distribution, the resistance change of the first sensing resistor 201 is , the resistance change of the second sensing resistor 202 is , the resistance change of the third sensing resistor 203 is , the resistance change of the fourth sensing resistor 204 is , under this pressure, the first output terminal Vout + and the second output terminal Vout - The potential difference is .

[0044] Based on this, by calibrating the first output terminal Vout + and the second output terminal Vout - The change in the potential difference can be used to detect the pressure.

[0045] Compared with the method of measuring pressure using a single sensing resistor, in the embodiment of the present application, four sensing resistors are electrically connected to form a Figure 2 The circuit structure shown in the figure calculates the pressure, which can avoid the influence of other environmental factors on the resistance change of the induction resistor, and further avoid the influence of other environmental factors on the pressure calculation result, which is beneficial to improve the accuracy of the calculation result.

[0046] In addition, the four sensing resistors all include nanowire structures, which are smaller in size, more obviously deformed when subjected to stress, and have higher sensitivity. Nanowire structures usually have a larger piezoresistance coefficient, and have a quantum confinement effect at the nanoscale, which can amplify the change in the piezoresistance effect after strain. For example, the piezoresistance coefficient of silicon nanowires is two orders of magnitude higher than that of conventional silicon piezoresistance coefficients, and the resistance value changes more significantly under the same force, so that the pressure sensor 10 can have a higher sensitivity. And based on the nanowire structure, the sensing resistor works well in high and low temperature environments, thereby improving the reliability of the pressure sensor 10.

[0047] In some embodiments, Figure 1 As shown, the shape of the orthographic projection of the cavity K0 on the first surface P1 is a circle. The length extension direction of the first sensing resistor 201, the length extension direction of the second sensing resistor 202, the length extension direction of the third sensing resistor 203 and the length extension direction of the fourth sensing resistor 204 are all the same as a certain diameter direction X of the circle.

[0048] In the embodiment of the present application, the shape of the positive projection of the cavity K0 on the first surface P1 is a circle. Under the action of pressure, the distribution of stress on the first surface P1 has a certain central symmetry, that is, the stress distribution is symmetrical along the center of the circle. In this circular area, the stresses at positions with equal distances from the center of the circle are equal in magnitude and different in direction. The stress at each position can be decomposed along the direction pointing to the center of the circle. In the embodiment of the present application, the length extension direction of the four induction resistors is the same, such as Figure 1As shown, the length extension direction of the second sensing resistor 202 and the length extension direction of the fourth sensing resistor 204 pass through the center of the circle, that is, the same as the diameter direction X of the circle. When the positions of the second sensing resistor 202 and the fourth sensing resistor 204 are symmetrical about the center of the circle, the forces on the two are equal and the directions are symmetrical along the center of the circle. Similarly, when the positions of the first sensing resistor 201 and the third sensing resistor 203 are symmetrical about the center of the circle, the forces on the two are equal and the directions are symmetrical along the center of the circle. When the distances from the centers of the four sensing resistors to the center of the circle are equal, the force on the first sensing resistor 201 is not equal to the force on the second sensing resistor 202 due to the size of the sensing resistors themselves.

[0049] By optimizing the positions of the four inductive resistors, the deformation of each inductive resistor can be made most obvious under the same pressure. Based on this, the equivalent circuit can have a certain degree of symmetry, which is convenient for simplifying calculations, and the difference in the resistance change in the equivalent circuit can be increased, thereby improving the calculation accuracy and sensitivity.

[0050] In some embodiments, the width of the sensing resistor ranges from 2 nm to 2000 nm.

[0051] That is, the width range of the nanowire structure is 2nm~2000nm, for example 2nm, 5nm, 10nm, 20nm...2000nm, etc. In different embodiments, the specific size can be optimized according to the size of the mass block to ensure the accuracy and sensitivity of the pressure sensor 10.

[0052] In some embodiments, Figure 3 As shown, the sensing resistor further includes a gate G, which is arranged between a source S and a drain D of the sensing resistor.

[0053] In the embodiment of the present application, the four sensing resistors all include a nanowire structure 22, and the nanowire structure 22 here can be regarded as a part of a transistor, so that the four sensing resistors have transistor-related characteristics. Exemplarily, by setting a gate G and applying a voltage equal to the transistor threshold voltage on the gate G, compensation of the sensing resistor in the equivalent circuit can be achieved, so that Figure 2 The equivalent circuit shown is closer to the ideal equivalent effect, further improving the sensitivity of the pressure sensor 10.

[0054] In some embodiments, Figure 3 As shown, the nanowire structure 22 further includes a stacked semiconductor layer 221 and a barrier layer 222. The material of the semiconductor layer 221 includes at least one of gallium nitride, gallium arsenide or indium gallium arsenide, and the material of the barrier layer 222 includes at least one of indium gallium nitride, aluminum gallium nitride, indium phosphide, aluminum gallium arsenide or indium aluminum arsenide.

[0055] The nanowire structure 22 formed by the above materials has a good quantum confinement effect. When the sensing resistor is deformed under stress, the nanowire structure is conducive to amplifying the piezoresistance change, so that the sensing resistor has a higher sensitivity. In addition, the above materials show good performance in both low and high temperature environments, which is conducive to improving the reliability of the sensing resistor. Based on this, the above materials can improve the sensitivity and reliability of the pressure sensor 10.

[0056] In some embodiments, Figure 4~Figure 5 As shown, Figure 4 A top view of another pressure sensor provided in an embodiment of the present application, Figure 5 for Figure 4 The source electrodes S and drain electrodes D of the plurality of sensing resistors are all located in the barrier layer 222, and the plurality of sensing resistors are electrically connected through the barrier layer 222, thus forming a Figure 2 The equivalent circuit shown is the same as the equivalent circuit.

[0057] In this embodiment, no additional metal wiring is required between the multiple sensing resistors. Instead, the conductivity of the barrier layer 222 is used to realize the electrical connection between the sensing resistors. By avoiding the design of metal wiring and reducing the use of metal materials, the reliability of the pressure sensor 10 in harsh environments can be improved. For example, in a high temperature, high humidity or highly corrosive environment, the metal wiring is prone to rust or temperature drift, which in turn affects the reliability of the pressure sensor 10. In this embodiment, by avoiding the use of metal materials, the reliability of the pressure sensor 10 can be improved, so that the pressure sensor 10 can be widely used in petrochemical, marine exploration, automobiles, aerospace and other application scenarios that are sensitive to corrosive media.

[0058] In some embodiments, Figure 3 or Figure 5 As shown, the pressure sensor 10 further includes a substrate 23 , and the substrate 23 is disposed on the second surface P2 .

[0059] The substrate 23 provides a flat surface for the pressure sensor 10, which is conducive to optimizing the conduction of stress on the substrate 21, and then optimizing the distribution of stress on the first surface P1. In addition, the substrate 23 can work together with the substrate 21 and multiple sensing resistors to form the cavity K0 on the substrate 21 into a closed cavity, so that a certain atmospheric pressure can be maintained in the cavity K0. When the external pressure conditions change, the sensing resistor in a suspended film state can undergo a slight deformation, thereby causing a change in resistance value.

[0060] In some embodiments, Figure 6 As shown, Figure 6This is a cross-sectional view of another pressure sensor provided in an embodiment of the present application. The pressure sensor 10 further includes a packaging shell 31 . The packaging shell 31 includes a chamber 32 . The sensor unit is disposed in the chamber 32 .

[0061] For example, the package shell 31 can be a corrosion-resistant tube shell, the sensor unit is arranged in the chamber 32 and fixed with corrosion-resistant glue, and the gold wire 33 is used to lead out the pad interface PAD of the sensor unit. The "pad interface PAD" here refers to the first input terminal Vin and the second input terminal GND, as well as the first output terminal Vout. + and the second output terminal Vout - In addition, the corrosion-resistant spin-coating liquid 34 also covers the gold wire 33, the sensor unit and the packaging shell 31 for corrosion protection. Exemplarily, the material of the corrosion-resistant spin-coating liquid 34 may include parylene or the like.

[0062] In a second aspect, the present application also provides a method for preparing a pressure sensor, such as Figure 7 As shown, Figure 7 A flow chart of a method for preparing a pressure sensor provided in an embodiment of the present application, Figure 8~Figure 23 A diagram of the steps for preparing a pressure sensor provided in an embodiment of the present application.

[0063] The preparation method comprises the following steps S10 to S20: Step S10: Figure 8~Figure 9 As shown, a plurality of sensing resistors are formed on a substrate 21 , and the sensing resistors include a nanowire structure 22 .

[0064] The plurality of sensing resistors include a first sensing resistor 201, a second sensing resistor 202, a third sensing resistor 203 and a fourth sensing resistor 204. The pressure sensor 10 further includes a first input terminal Vin and a second input terminal GND, and a first output terminal Vout. + and the second output terminal Vout - The source of the first sensing resistor 201 is electrically connected to the first input terminal Vin, and the drain of the first sensing resistor 201 is electrically connected to the first output terminal Vout. + The source of the second sensing resistor 202 is electrically connected, the drain of the second sensing resistor 202 is electrically connected to the second input terminal GND and the drain of the third sensing resistor 203, and the source of the third sensing resistor 203 is electrically connected to the second output terminal Vout. - The first sensing terminal 204 is electrically connected to the drain of the fourth sensing resistor 204 , and the source of the fourth sensing resistor 204 is electrically connected to the first input terminal Vin.

[0065] For example, Figure 8As shown, the substrate 21 includes a first surface P1 and a second surface P2 opposite to each other. To avoid lattice mismatch and dislocation, a buffer layer 24 is usually disposed on the first surface P1 of the substrate 21.

[0066] Then Fig. 9 As shown, a nanowire structure 22 is formed on a side of the buffer layer 24 away from the substrate 21 .

[0067] Exemplarily, along the direction Z gradually away from the substrate 21, the nanowire structure 22 includes a semiconductor layer 221 and a barrier layer 222 stacked in sequence. In some embodiments, the semiconductor layer 221 and the barrier layer 222 can be sequentially prepared by vapor deposition according to the required size and position of the nanowire structure 22. In other embodiments, the semiconductor layer 221 and the barrier layer 222 can also be sequentially prepared on the side of the buffer layer 24 away from the substrate 21, and then etched by an inductively coupled plasma etching process to form the desired nanowire structure 22.

[0068] The substrate 21 is usually a silicon substrate, or may also be a sapphire substrate. The width of the nanowire structure 22 ranges from 2 nm to 2000 nm.

[0069] In order to form a good electrical contact, Fig.10 As shown, an ohmic contact layer 25 is first formed on one side of both ends of the nanowire structure 22 away from the substrate 21. Exemplarily, the material of the ohmic contact layer 25 may include at least one of titanium, aluminum, nickel, gold, and the like.

[0070] Afterwards, if Fig.11 As shown, a first passivation layer 26 is formed, and the first passivation layer 26 exposes a portion of the ohmic contact layer 25 .

[0071] Then, if Fig.12 As shown, metal material is deposited to form a source S and a drain D.

[0072] In some embodiments, during the process of forming the source S and the drain D, a gate G is also formed. The gate G is disposed between the source S and the drain D of the sensing resistor, and finally forms a gate electrode as shown in FIG. Figure 3 The pressure sensor 10 shown is not illustrated here.

[0073] In the process of forming the source S and the drain D, a connection line is also formed synchronously, so that the source S and the drain D of the plurality of sensing resistors are respectively electrically connected to form a Figure 2 The equivalent circuit is shown.

[0074] The metal material used in the above steps of forming the source electrode S, the drain electrode D and the connecting wire is preferably a corrosion-resistant material such as titanium, nickel, or gold.

[0075] Afterwards, if Fig.13 As shown, a second passivation layer 27 is formed to insulate and protect the multiple sensing resistors and connecting wires. The second passivation layer 27 forms a suitable pad opening for connecting an external power source.

[0076] Step S20: Fig.14 As shown, the substrate 21 is etched to form a cavity K0 penetrating the substrate. The orthographic projections of the plurality of sensing resistors on the substrate 21 are located within the region where the cavity K0 is located.

[0077] Finally, if Fig.15 As shown, the substrate 23 can be bonded to the second surface P2 of the substrate 21 by silicon-silicon bonding. The material of the substrate 23 includes but is not limited to silicon, quartz, etc. Exemplarily, the size of the substrate 23 along the direction X is the same as the size of the substrate 21 along the direction X in step S10, and the size of the substrate 23 along the direction Y is the same as the size of the substrate 21 along the direction Y in step S10. That is, the orthographic projection of the substrate 23 can coincide with the orthographic projection of the substrate 21.

[0078] In some other embodiments, the electrical connection between the multiple sensing resistors is no longer designed with metal wiring, but is implemented by using the barrier layer 222 .

[0079] For example, Figure 16 to Figure 23 As shown, the step of forming a plurality of sensing resistors on the substrate 21 includes the following steps S11 to S13: Step S11: Fig.16 As shown, a semiconductor layer 221 is formed on a substrate 21 .

[0080] Step S12: Fig.17 As shown, a barrier layer 222 is formed on a side of the semiconductor layer 221 away from the substrate 21 .

[0081] Then as Fig.18 As shown, the barrier layer 222 is thinned to enhance the piezoresistive effect.

[0082] Step S13: Fig.19 As shown, the barrier layer 222 is etched to form a plurality of source electrodes S and drain electrodes D of the sensing resistors, and a plurality of connecting wires, wherein the plurality of sensing resistors are electrically connected through the plurality of connecting wires.

[0083] Here, it can be understood that by etching the barrier layer 222, a plurality of nanowire structures of sensing resistors are obtained, and the two ends of the nanowire structure correspond to the source S and the drain D of the sensing resistor respectively. Two adjacent nanowire structures are connected together through the unetched barrier layer 222. Here, the barrier layer 222 that serves as a connection between the two nanowire structures is the connecting wire mentioned above.

[0084] Afterwards, if Fig. 20 As shown, in order to form a good electrical contact, an ohmic contact layer 25 is first formed on the side of the barrier layer 222 away from the substrate 21. The material of the ohmic contact layer 25 may include at least one of titanium, aluminum, nickel, gold, etc.

[0085] Then, if Fig.21 As shown, a pad interface PAD is formed on the side of the ohmic contact layer 25 away from the substrate 21. The metal material used in this step is preferably a corrosion-resistant material such as titanium, nickel, or gold. The "pad interface PAD" here refers to the first input terminal Vin and the second input terminal GND, as well as the first output terminal Vout. + and the second output terminal Vout - .

[0086] Afterwards, if Fig. 22 As shown, the substrate 21 is etched to form a cavity K0 penetrating the substrate. The orthographic projections of the plurality of sensing resistors on the substrate 21 are located within the region where the cavity K0 is located.

[0087] Finally, if Fig.23 As shown, the base 23 may be bonded to the second surface P2 of the substrate 21 by silicon-silicon bonding.

[0088] In some other embodiments, corrosion-resistant packaging technology can be used to further improve corrosion resistance and increase service life. Figure 6 As shown, a corrosion-resistant packaging shell 31 is provided, and the bottom of the sensor unit is fixed in the packaging shell 31 by using corrosion-resistant glue. In addition, the pad interface PAD of the sensor unit is electrically connected to the packaging shell 31 by using a gold wire 33. Finally, a corrosion-resistant spin coating liquid 34 such as parylene is used to cover the surface of the gold wire 33, the sensor unit and the packaging shell 31 for corrosion protection.

[0089] In the above application embodiments, the preparation method is relatively simple. Compared with the traditional technology that the processing of silicon-based materials is relatively complicated and the piezoresistance coefficient is relatively small, the embodiment of the present application can increase the sensitivity and simplify the preparation method by preparing a nanowire structure, which is beneficial to saving costs and improving cost performance. The pressure sensor prepared according to the above method has higher sensitivity and reliability.

[0090] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that a person skilled in the art can think of within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A pressure sensor, characterized in that: comprising at least one sensor unit; The sensor unit comprises: A substrate including a first surface and a second surface opposite to each other, and a cavity extending through the first surface and the second surface; A plurality of sensing resistors are disposed on the first surface, wherein the sensing resistors include nanowire structures; orthographic projections of the plurality of sensing resistors on the first surface are located within the range of orthographic projections of the cavity on the first surface; Wherein, the plurality of sensing resistors include a first sensing resistor, a second sensing resistor, a third sensing resistor and a fourth sensing resistor, and the pressure sensor further includes a first input terminal and a second input terminal, and a first output terminal and a second output terminal; A source of the first sensing resistor is electrically connected to the first input terminal, a drain of the first sensing resistor is electrically connected to the first output terminal and a source of the second sensing resistor, a drain of the second sensing resistor is electrically connected to the second input terminal and a drain of the third sensing resistor, a source of the third sensing resistor is electrically connected to the second output terminal and a drain of the fourth sensing resistor, and a source of the fourth sensing resistor is electrically connected to the first input terminal.

2. The pressure sensor according to claim 1, characterized in that: The shape of the orthographic projection of the cavity on the first surface is a circle; The length extension direction of the first sensing resistor, the length extension direction of the second sensing resistor, the length extension direction of the third sensing resistor, and the length extension direction of the fourth sensing resistor are all the same as a certain diameter direction of the circle.

3. The pressure sensor according to claim 1, characterized in that: The width of the inductive resistor ranges from 2nm to 2000nm.

4. The pressure sensor according to claim 1, characterized in that: The sensing resistor further includes a gate, and the gate is arranged between a source and a drain of the sensing resistor.

5. The pressure sensor according to claim 1, characterized in that: The nanowire structure further includes a semiconductor layer and a barrier layer which are stacked; The material of the semiconductor layer includes at least one of gallium nitride, gallium arsenide or indium gallium arsenide, and the material of the barrier layer includes at least one of indium gallium nitride, aluminum gallium nitride, indium phosphide, aluminum gallium arsenide or indium aluminum arsenide.

6. The pressure sensor according to claim 5, characterized in that: Sources and drains of the plurality of sensing resistors are located in the barrier layer, and the plurality of sensing resistors are electrically connected through the barrier layer.

7. The pressure sensor according to claim 1, characterized in that: The pressure sensor further includes a substrate disposed on the second surface.

8. The pressure sensor according to claim 1, characterized in that: The pressure sensor further includes a packaging shell, the packaging shell includes a cavity, and the sensor unit is disposed in the cavity.

9. A method for preparing a pressure sensor, characterized in that: include: forming a plurality of sensing resistors on a substrate, wherein the sensing resistors include nanowire structures; Etching the substrate to form a cavity penetrating the substrate; The orthographic projections of the plurality of sensing resistors on the substrate are located within the region where the cavity is located; Wherein, the plurality of sensing resistors include a first sensing resistor, a second sensing resistor, a third sensing resistor and a fourth sensing resistor, and the pressure sensor further includes a first input terminal and a second input terminal, and a first output terminal and a second output terminal; A source of the first sensing resistor is electrically connected to the first input terminal, a drain of the first sensing resistor is electrically connected to the first output terminal and a source of the second sensing resistor, a drain of the second sensing resistor is electrically connected to the second input terminal and a drain of the third sensing resistor, a source of the third sensing resistor is electrically connected to the second output terminal and a drain of the fourth sensing resistor, and a source of the fourth sensing resistor is electrically connected to the first input terminal.

10. The preparation method according to claim 9, characterized in that: A plurality of sensing resistors are formed on the substrate, including: forming a semiconductor layer on the substrate; forming a barrier layer on a side of the semiconductor layer away from the substrate; Etching the barrier layer to form source electrodes and drain electrodes of the plurality of sensing resistors, and a plurality of connecting lines; Wherein, the multiple sensing resistors are electrically connected through the multiple connecting lines.

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