CN116448290A - High-frequency dynamic MEMS piezoresistive pressure sensor and preparation method thereof - Google Patents

Abstract

The invention relates to the technical field of pressure sensors, and specifically discloses a high-frequency dynamic MEMS piezoresistive pressure sensor and a preparation method thereof. The high-frequency dynamic MEMS piezoresistive pressure sensor includes a substrate, a first substrate and a pressure-sensitive film, and a pressure The sensitive thin film is arranged on the first substrate, and the first substrate is arranged on the base; the pressure sensitive thin film includes a piezoresistor, an ohmic contact area, a first passivation layer, a second passivation layer, a pressure sensitive electrode layer, The third passivation layer, the first driving electrode layer, the first dielectric layer, the second driving electrode layer, the fourth passivation layer, the fifth passivation layer, the first strain electrode layer and the second dielectric layer. The high-frequency dynamic MEMS piezoresistive pressure sensor provided by the present invention can effectively improve the high-frequency dynamic characteristics of the MEMS piezoresistive pressure sensor, reduce or even eliminate the impact of the external environment on the sensor, and reduce the zero bias and pressure of the pressure sensor. Temperature drift, improve the accuracy of the pressure sensor.

Description

A high-frequency dynamic MEMS piezoresistive pressure sensor and its preparation method

technical field

The invention relates to the technical field of pressure sensors, in particular to a high-frequency dynamic MEMS piezoresistive pressure sensor and a preparation method thereof.

Background technique

Pressure is one of the important physical parameters that modern measurement and control technology needs to pay attention to. With the development of modern measurement and control technology, the requirements for dynamic measurement in high-frequency environments have also increased, and traditional pressure sensors are difficult to meet the requirements of high-frequency dynamic pressure measurement. Require. In the face of more specific situations, such as aerospace, medical electronics, weapon control, artificial intelligence and other fast and high-frequency environments, what needs to be tested is the extremely fast-changing transient pressure signal.

MEMS (Micro-Electro-Mechanical System, Micro-Electro-Mechanical System) piezoresistive pressure sensor uses the piezoresistive effect of semiconductor materials to form a Wheatstone bridge by interconnecting semiconductor materials to convert mechanical signals into electrical signals. Measurement. Compared with other traditional pressure sensors, MEMS piezoresistive pressure sensors already have better high-frequency dynamic characteristics, but with the high-speed post-processing circuit, the dynamic measurement capability of the current MEMS piezoresistive pressure sensors has gradually become a system The short board in the middle cannot meet the growing business needs, and there are still problems of long setup time and response time. Therefore, high-frequency dynamic characteristics need to be taken into consideration in the design.

In addition, different fields of use also have a corresponding impact on the measurement accuracy of the pressure sensor. Such as temperature changes or shocks. Changes in temperature in the environment will cause changes in stress due to thermal expansion. With significant temperature changes, the nonlinearity of measurement will become extremely serious, which restricts the measurement accuracy and application range of the pressure sensor. Existing solutions generally add additional temperature sensing devices and use empirical formulas to compensate the results, but correspondingly, these designs pose some challenges to the size of the sensor. At the same time, this kind of discrete measurement can only infer thermal stress through temperature values. The nonlinearity of the function relationship will change with the change of the external pressure. When the thermal stress and the external pressure coexist, there will be a certain error in the measurement, which will have a certain impact on the measurement accuracy of the sensor.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the prior art, and provide a high-frequency dynamic MEMS piezoresistive pressure sensor and a preparation method for a high-frequency dynamic MEMS piezoresistive pressure sensor, which can effectively improve the performance of the MEMS piezoresistive pressure sensor. High-frequency dynamic characteristics, and can reduce or even eliminate the impact of the external environment on the sensor, reduce the zero bias and temperature drift of the pressure sensor, and improve the accuracy of the pressure sensor.

As one aspect of the present invention, a high-frequency dynamic MEMS piezoresistive pressure sensor is provided, including a base, a first substrate, and a pressure-sensitive film, the pressure-sensitive film is arranged on the first substrate, and the first a substrate is disposed on the base;

Wherein, the pressure-sensitive thin film includes a piezoresistor, an ohmic contact area, a first passivation layer, a second passivation layer, a pressure-sensitive electrode layer, a third passivation layer, a first driving electrode layer, a first dielectric layer , the second driving electrode layer, the fourth passivation layer, the fifth passivation layer, the first strain electrode layer and the second dielectric layer, four piezoresistors and eight ohmic contacts are arranged on the first substrate regions, the eight ohmic contact regions are respectively located at both ends of the short sides of the four varistors, the first substrate and the upper surface of the varistors are formed with the first passivation layer, so The second passivation layer is formed on the upper surface of the first passivation layer, and a hole is opened on the first passivation layer and the second passivation layer corresponding to the ohmic contact region to expose the ohmic contact area, the pressure-sensitive electrode layer is formed on the upper surface of the ohmic contact area and the second passivation layer by photolithography and magnetron sputtering a layer of copper, so as to connect the four pressure-sensitive resistors into a benefit Stone bridge, the third passivation layer is formed on the upper surface of the second passivation layer and the pressure-sensitive electrode layer, and the first driving electrode layer is formed on the upper surface of the third passivation layer, so The first dielectric layer is formed on the upper surface of the third passivation layer and the first driving electrode layer, the second driving electrode layer is formed on the upper surface of the first dielectric layer, and the first dielectric layer is formed on the upper surface of the first dielectric layer. The fourth passivation layer is formed on the upper surface of the electrical layer and the second driving electrode layer, and the first groove and the second groove are sequentially opened on the back surface of the first substrate, and the lower surface of the first groove is The fifth passivation layer, the first strain electrode layer and the second dielectric layer are sequentially formed on the surface;

Wherein, the base includes a second substrate, a sixth passivation layer, a second strained electrode layer and a third dielectric layer, and the sixth passivation layer is formed on the upper surface of the central part of the second substrate, The second strained electrode layer is formed on the upper surface of the sixth passivation layer, the third dielectric layer is formed on the upper surfaces of the sixth passivation layer and the second strained electrode layer, and the first The substrate and the second substrate are connected by anodic bonding, and the central part of the second substrate, the sixth passivation layer, the second strain electrode layer and the third dielectric layer are all located in the second groove middle.

Further, the material of the first substrate is single crystal silicon with a thickness of 50-300 μm; the material of the varistor is lightly doped B silicon; the material of the eight ohmic contact regions is heavily doped Silicon of B; the material of the first passivation layer is silicon dioxide, with a thickness of 100nm-1μm; the material of the second passivation layer is silicon nitride, with a thickness of 100nm-1um; the pressure-sensitive electrode layer The material of the passivation layer is copper with a thickness of 100nm-300nm; the material of the third passivation layer is silicon dioxide with a thickness of 1-5um; the material of the first driving electrode layer is metal with a thickness of 50nm-200nm; The material of the first dielectric layer is a material with a high dielectric constant, with a thickness of 50-150nm; the material of the second driving electrode layer is metal, with a thickness of 50nm-200nm; the material of the fourth passivation layer silicon dioxide with a thickness of 1-5um; the material of the fifth passivation layer is silicon dioxide with a thickness of 1-6um; the material of the first strain electrode layer is metal with a thickness of 50-200nm; The material of the second dielectric layer is a material with a high dielectric constant, and the thickness is 50-200nm.

Further, the first driving electrode layer, the first dielectric layer and the second driving electrode layer constitute a driving capacitor for providing electrostatic force.

Further, the depth of the first groove is 45um-270um, and the depth of the second groove is 43um-258um.

Further, the material of the second substrate is glass with a thickness of 50-300 μm; the material of the sixth passivation layer is silicon nitride with a thickness of 1 um-6 um; the material of the second strain electrode layer is The metal has a thickness of 50-200nm; the material of the third dielectric layer is a material with a high dielectric constant and the thickness is 50-200nm.

Further, the second strain electrode layer includes a plurality of metal blocks not connected to each other, so as to measure strains in different regions.

Further, the first strained electrode layer, the second dielectric layer, the third dielectric layer and the second strained electrode layer form a strain detection capacitance, wherein the position of the second strained electrode layer remains unchanged, and the first strained electrode layer The position of the strain electrode layer changes due to the pressure, which causes the capacitance value to change and realizes the measurement of strain.

As another aspect of the present invention, a method for preparing a high-frequency dynamic MEMS piezoresistive pressure sensor is provided, wherein the method for preparing the high-frequency dynamic MEMS piezoresistive pressure sensor includes:

providing a first substrate and a base;

preparing a pressure-sensitive thin film on the first substrate;

The upper surface of the base and the lower surface of the first substrate are bonded by anodic bonding.

Further, it also includes:

Also includes:

Step a: select a 300mm thick N-type (100) silicon wafer as the first substrate, and form a lightly doped B varistor on the first substrate through photolithography and ion implantation;

Step b: forming heavily B-doped ohmic contact regions on both sides of the varistor on the first substrate by photolithography and ion implantation;

Step c: respectively growing 100 nm of silicon oxide and 100 nm of silicon nitride on the upper surface of the first substrate by low pressure chemical vapor deposition method LPCVD as the first passivation layer and the second passivation layer;

Step d: Etching the first passivation layer and the second passivation layer by photolithography and reactive ion etching RIE to expose the ohmic contact region, and by photolithography and magnetron sputtering a layer thickness of 100nm- 300nm copper, forming a pressure-sensitive electrode layer on the upper surface of the ohmic contact region and the second passivation layer, so as to connect four piezoresistors into a Wheatstone bridge;

Step e: growing a layer of silicon oxide with a thickness of 2um on the upper surface of the second passivation layer and the pressure-sensitive electrode layer by photolithography and low-pressure chemical vapor deposition method LPCVD as a third passivation layer;

Step f: sputtering a layer of copper with a thickness of 100 nm on the upper surface of the third passivation layer by photolithography and magnetron sputtering, as the first driving electrode layer;

Step g: growing a layer of hafnium-zirconium composite oxide with a thickness of 50-150 nm on the upper surface of the third passivation layer and the first driving electrode layer by atomic layer deposition ALD as the first dielectric layer;

Step h: sputtering a layer of copper with a thickness of 100 nm on the upper surface of the first dielectric layer by photolithography and magnetron sputtering, as the second driving electrode layer;

Step i: growing a layer of silicon oxide with a thickness of 2um on the upper surfaces of the first dielectric layer and the second driving electrode layer by LPCVD as a fourth passivation layer;

Step j: etching the ICP by photolithography and inductively coupled plasma, and etching a first groove with a depth of 270um on the back surface of the first substrate;

Step k: growing a layer of silicon oxide with a thickness of 1 μm on the lower surface of the first groove by photolithography and low-pressure chemical vapor deposition method LPCVD as the fifth passivation layer;

Step 1: sputtering a layer of copper with a thickness of 100 nm on the lower surface of the fifth passivation layer by photolithography and magnetron sputtering, as the first strained electrode layer;

Step m: growing a layer of hafnium-zirconium composite oxide with a thickness of 50 nm on the lower surface of the first strained electrode layer by photolithography and atomic layer deposition ALD as the second dielectric layer;

Step n: etching the ICP by photolithography and inductively coupled plasma, etching a second groove with a depth of 258um on the back surface of the first substrate, the cross-sectional area of the second groove is larger than that of the first substrate a groove;

Step o: Take another piece of glass sheet with a thickness of 300um, etch the ICP by photolithography and inductively coupled plasma to obtain a ladder structure as the second substrate, wherein the size of the middle part of the second substrate is smaller than that of the first substrate. The size of the groove, the middle part of the second substrate is 258um higher than the height of the edge part;

Step p: growing a layer of silicon nitride with a thickness of 1 μm on the upper surface of the middle thicker part of the second substrate by photolithography and low-pressure chemical vapor deposition method LPCVD, as the sixth passivation layer;

Step q: Sputtering a layer of copper with a thickness of 100 nm on the upper surface of the sixth passivation layer by photolithography and magnetron sputtering as the second strained electrode layer;

Step r: growing a layer of hafnium-zirconium composite oxide with a thickness of 50nm-100nm on the upper surface of the sixth passivation layer and the second strained electrode layer by photolithography and atomic layer deposition ALD, as the third dielectric layer;

Step s: Bonding the first substrate and the second substrate by anodic bonding to complete the preparation of the high-frequency dynamic MEMS piezoresistive pressure sensor.

The present invention has the following beneficial effects:

1. The present invention uses the drive electrode to provide electrostatic force for the pressure-sensitive film, and can apply an auxiliary force of corresponding direction and size when the deformation is generated, restored, and oscillated, shortening the time of its movement, and further improving the high-frequency dynamics of the pressure sensor. characteristic;

2. The present invention constructs a measurement-control feedback system through the driving electrodes and strain detection electrodes, which can realize the detection and control of the movement and deformation of the sensitive film, thereby reducing the undesired film deformation, such as zero bias, temperature drift or The bias brought by the impact acceleration improves the bias performance of the device;

3. The present invention can timely obtain and compensate for the additional stress and strain caused by temperature through the measurement feedback system. On the one hand, compared with traditional pressure-sensitive devices, adding a temperature sensor reduces the size of the device. On the other hand, the temperature sensor only It can be measured and corrected in the later data, and the present invention can realize control through electrostatic force;

4. Through the measurement feedback system, the present invention can know the deformation of the pressure-sensitive film in time and give feedback, avoiding damage to the device due to excessive input, and improving the anti-overload capability of the device;

5. By supplementing a strain gauge detection electrode, the present invention can obtain the resistance change of the piezoresistor due to geometry through the thin film strain data, thereby improving the precision of the pressure sensor;

6. The present invention is prepared by MEMS technology, and the sensor has the advantages of small size, high precision, good consistency, easy mass production and low cost.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the description, together with the following specific embodiments, are used to explain the present invention, but do not constitute a limitation to the present invention.

FIG. 1 is a top view of a piezoresistor of a high-frequency dynamic MEMS piezoresistive pressure sensor in an embodiment of the present invention.

FIG. 2 is a schematic diagram of Wheatstone bridge connection of piezoresistors of a high-frequency dynamic MEMS piezoresistive pressure sensor in an embodiment of the present invention.

Fig. 3 is a cross-sectional view of a high-frequency dynamic MEMS piezoresistive pressure sensor along the section line AA' shown in Fig. 1 in an embodiment of the present invention.

Fig. 4 is a schematic structural diagram corresponding to the preparation step a in the embodiment of the present invention.

Fig. 5 is a schematic structural diagram corresponding to the preparation step b in the embodiment of the present invention.

Fig. 6 is a schematic structural diagram corresponding to preparation step c in the embodiment of the present invention.

Fig. 7 is a schematic structural diagram corresponding to the preparation step d in the embodiment of the present invention.

Fig. 8 is a schematic structural diagram corresponding to the preparation step e in the embodiment of the present invention.

Fig. 9 is a schematic structural diagram corresponding to the preparation step f in the embodiment of the present invention.

Fig. 10 is a schematic structural diagram corresponding to the preparation step g in the embodiment of the present invention.

Fig. 11 is a schematic structural diagram corresponding to the preparation step h in the embodiment of the present invention.

Fig. 12 is a schematic structural diagram corresponding to the preparation step i in the embodiment of the present invention.

Fig. 13 is a schematic structural diagram corresponding to preparation step j in the embodiment of the present invention.

Fig. 14 is a schematic structural diagram corresponding to the preparation step k in the embodiment of the present invention.

Fig. 15 is a schematic structural diagram corresponding to the preparation step 1 in the embodiment of the present invention.

Fig. 16 is a schematic structural diagram corresponding to the preparation step m in the embodiment of the present invention.

Fig. 17 is a schematic structural diagram corresponding to preparation step n in the embodiment of the present invention.

Fig. 18 is a schematic structural diagram corresponding to the preparation step o in the embodiment of the present invention.

Fig. 19 is a schematic structural diagram corresponding to the preparation step p in the embodiment of the present invention.

Fig. 20 is a schematic structural diagram corresponding to the preparation step q in the embodiment of the present invention.

Fig. 21 is a schematic structural diagram corresponding to the preparation step r in the embodiment of the present invention.

Fig. 22 is a schematic structural diagram corresponding to the preparation step s in the embodiment of the present invention.

In the accompanying drawings, the list of components represented by each label is as follows: 1-first substrate; 2-varistor; 3-ohmic contact area; 4-first passivation layer; 5-second passivation layer; 6- Pressure-sensitive electrode layer; 7-third passivation layer; 8-first driving electrode layer; 9-first dielectric layer; 10-second driving electrode layer; 11-fourth passivation layer; 12-first concave Groove; 13-fifth passivation layer; 14-first strain electrode layer; 15-second dielectric layer; 16-second groove; 17-second substrate; 18-sixth passivation layer; 19- The second strain electrode layer; 20 - the third dielectric layer.

Detailed ways

It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and examples.

In order to enable those skilled in the art to better understand the solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only Embodiments of some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

It should be noted that the terms "first" and "second" in the description and claims of the present invention and the above drawings are used to distinguish similar objects, but not necessarily used to describe a specific sequence or sequence. It should be understood that the data so used may be interchanged under appropriate circumstances for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having", as well as any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or device comprising a series of steps or elements that is not necessarily limited to the explicitly listed instead, may include other steps or elements not explicitly listed or inherent to the process, method, product or apparatus.

In the embodiment of the present invention, a high-frequency dynamic MEMS piezoresistive pressure sensor is provided. As shown in Fig. 1-3, the high-frequency dynamic MEMS piezoresistive pressure sensor includes a substrate, a first substrate 1 and a pressure sensitive a thin film, the pressure-sensitive thin film is disposed on the first substrate 1, and the first substrate 1 is disposed on the base;

Wherein, the pressure-sensitive thin film includes a piezoresistor 2, an ohmic contact area 3, a first passivation layer 4, a second passivation layer 5, a pressure-sensitive electrode layer 6, a third passivation layer 7, a first driving electrode layer 8. The first dielectric layer 9, the second driving electrode layer 10, the fourth passivation layer 11, the fifth passivation layer 13, the first strain electrode layer 14 and the second dielectric layer 15, the first substrate 1 is provided with four varistors 2 and eight ohmic contact areas 3, and the eight ohmic contact areas 3 are respectively located at both ends of the short sides of the four varistors 2, and the first substrate 1 and The upper surface of the varistor 2 is formed with the first passivation layer 4, the upper surface of the first passivation layer 4 is formed with the second passivation layer 5, and the first passivation layer 4 On the second passivation layer 5 corresponding to the position of the ohmic contact area 3, a hole is opened to expose the ohmic contact area 3, and a layer of copper is formed between the ohmic contact area 3 and the ohmic contact area 3 by photolithography and magnetron sputtering. The upper surface of the second passivation layer 5 forms the pressure-sensitive electrode layer 6, so as to connect the four piezoresistors 2 into a Wheatstone bridge, the second passivation layer 5 and the pressure-sensitive electrode layer 6 The upper surface is formed with the third passivation layer 7, the upper surface of the third passivation layer 7 is formed with the first driving electrode layer 8, the third passivation layer 7 and the first driving electrode layer 8 The first dielectric layer 9 is formed on the upper surface of the first dielectric layer 9, the second driving electrode layer 10 is formed on the upper surface of the first dielectric layer 9, the first dielectric layer 9 and the second driving electrode layer The fourth passivation layer 11 is formed on the upper surface of the first substrate 1, the first groove 12 and the second groove 16 are sequentially opened on the back surface of the first substrate 1, and the lower surface of the first groove 12 is sequentially formed. The fifth passivation layer 13 , the first strain electrode layer 14 and the second dielectric layer 15 are formed.

Preferably, the base includes a second substrate 17, a sixth passivation layer 18, a second strain electrode layer 19 and a third dielectric layer 20, and the upper surface of the central part of the second substrate 17 is formed with the The sixth passivation layer 18, the second strain electrode layer 19 is formed on the upper surface of the sixth passivation layer 18, and the upper surface of the sixth passivation layer 18 and the second strain electrode layer 19 is formed with a The third dielectric layer 20, the first substrate 1 and the second substrate 17 are connected by anodic bonding, the central part of the second substrate 17, the sixth passivation layer 18, the second strain Both the electrode layer 19 and the third dielectric layer 20 are located in the second groove 16 .

Preferably, the material of the first substrate 1 is single crystal silicon with a thickness of 50-300 μm; Silicon, B refers to boron, the purpose is to achieve higher sensitivity; the material of the eight ohmic contact regions 3 is silicon heavily doped with B, the purpose is to realize the electrode extraction of the piezoresistor 2; the first passivation The material of the layer 4 is silicon dioxide with a thickness of 100nm-1μm; the material of the second passivation layer 5 is silicon nitride with a thickness of 100nm-1um; the material of the pressure-sensitive electrode layer 6 is copper with a thickness of For 100nm-300nm, the purpose is to form a Wheatstone bridge connection of the piezoresistor.

Preferably, the material of the third passivation layer 7 is silicon dioxide with a thickness of 1-5um; the material of the first driving electrode layer 8 is metal, preferably Cu, Ti, Ni, Cr, Au, W At least one of these, the thickness is 50nm-200nm.

Preferably, the material of the first dielectric layer 9 is a material with a high dielectric constant, such as hafnium-zirconium composite oxide, hafnium-aluminum composite oxide, composite PVDF (nanofibers or nanosheets doped with barium titanate or titanium dioxide ), etc., or a multilayer composite structure composed of such materials, because it has a higher dielectric constant and better mechanical properties, and the total thickness is 50-150nm.

Preferably, the material of the second driving electrode layer 10 is metal, preferably at least one of Cu, Ti, Ni, Cr, Au, W, etc., and the thickness is 50nm-200nm.

Preferably, the material of the fourth passivation layer 11 is silicon dioxide with a thickness of 1-5um, the purpose is to serve as a protective layer; the material of the fifth passivation layer 13 is silicon dioxide with a thickness of 1-6um , the purpose is to form electrical isolation and passivation protection, to avoid substrate leakage current; the material of the first strain electrode layer 14 is a metal, preferably a metal with a high melting point, such as Cu, W, Cr, Ti, etc., with a thickness of 50 -200nm.

Preferably, the material of the second dielectric layer 15 is a material with a high dielectric constant, such as hafnium-zirconium composite oxide, hafnium-aluminum composite oxide, composite PVDF (nanofibers or nanosheets doped with barium titanate or titanium dioxide ), etc., or for their multilayer composite structure, because of its higher dielectric constant and better mechanical properties, with a total thickness of 50-200nm.

Specifically, the purpose of the third passivation layer 7 is to form electrical isolation between the pressure-sensitive electrode layer 6 and the first driving electrode layer 8 .

Preferably, the first driving electrode layer 8 , the first dielectric layer 9 and the second driving electrode layer 10 constitute a driving capacitor for providing electrostatic force. By controlling the frequency and phase of the applied voltage, the movement of the membrane can be influenced and controlled, thereby reducing the establishment time and recovery time of the pressure sensor and improving the dynamic measurement capability of the pressure sensor.

Specifically, the thickness of the first dielectric layer 9 is much smaller than the thickness of the third passivation layer 7, in order to ignore the electrostatic force between the pressure-sensitive electrode layer 6 and the first driving electrode layer 8 as much as possible. .

Specifically, the purpose of the first dielectric layer 9 is to form electrical isolation between the first driving electrode layer 8 and the second driving electrode layer 10 , and to serve as a dielectric for driving capacitance.

Preferably, the depth of the first groove 12 is 45um-270um, and the depth of the second groove 16 is 43um-258um.

Preferably, the material of the second substrate 17 is glass, with a thickness of 50-300 μm; the material of the sixth passivation layer 18 is silicon nitride, with a thickness of 1 um-6 um, the purpose is to serve as a protective layer; The material of the second strain electrode layer 19 is a metal, preferably a metal with a high melting point, such as Cu, W, Cr, Ti, etc., with a thickness of 50-200 nm; the material of the third dielectric layer 20 is a material with a high dielectric constant materials, such as hafnium-zirconium composite oxides, hafnium-aluminum composite oxides, composite PVDF (nanofibers or nanosheets doped with barium titanate or titanium dioxide), etc., or their multilayer composite structures because of their higher Dielectric constant and better mechanical properties, the total thickness is 50-200nm.

Preferably, the second strain electrode layer 19 includes a plurality of metal blocks that are not connected to each other, so as to measure strain in different regions and obtain higher measurement accuracy.

Further, the first strain electrode layer 14 , the second dielectric layer 15 , the third dielectric layer 20 and the second strain electrode layer 19 form a strain detection capacitor. According to the theoretical formula of capacitance, its capacitance value and the distance between the first strained electrode layer 14 and the second strained electrode layer 19 satisfy a certain mathematical relationship (the capacitance value is proportional to the reciprocal of the electrode spacing). Wherein the position of the second strained electrode layer 19 remains unchanged, the first strained electrode layer 14 is pressed down due to pressure, and the distance between the first strained electrode layer 14 and the second strained electrode layer 19 decreases , thus causing the capacitance value of the strain detection capacitor to change, the voltage change can be obtained by the relevant C-V (capacitance-to-voltage) conversion circuit, and the strain measurement can be realized through mathematical model analysis.

Further, the purpose of the second dielectric layer 15 and the third dielectric layer 20 is to serve as the protective layer of the first strain electrode layer 14 and the second strain electrode layer 19 and as the dielectric of the strain detection capacitance.

The working principle of the high-frequency dynamic MEMS piezoresistive pressure sensor in the embodiment of the present invention is as follows:

The pressure-sensitive film is deformed under the action of external pressure. Based on the piezoresistive effect, the resistance value of the piezoresistor 2 on the pressure-sensitive film changes accordingly, and the resistance value change of the piezoresistor 2 is converted through the Wheatstone bridge. It is a voltage output, so as to realize the conversion of pressure signal to electrical signal.

For the present invention, the electrostatic force is supplied by adding the first driving electrode layer 8 and the second driving electrode layer 10 of the driving electrode. When the pressure-sensitive film is deformed, a force in the same direction as the external pressure is applied through the electrostatic force to make it move. When the external pressure is removed and the pressure-sensitive film needs to be restored, the direction of the driving voltage is changed to increase the acceleration of the recovery, thus realizing the establishment time and recovery time. decrease. On the other hand, according to the principle of mechanical vibration, when the pressure-sensitive film moves to the equilibrium position, it will continue to weaken the oscillation at the equilibrium position because it still has speed, which also affects the accuracy of the sensor and the repeatability of the test to a certain extent. , and the method of controlling the electrostatic force through electrodes can well weaken this effect.

Furthermore, combining and utilizing the principle of the strain gauge pressure sensor, a strain detection capacitance is added to the back cavity of the pressure sensor. Its role mainly has two points. Firstly, the strain of the pressure-sensitive film is used to bring the strain of the first strain electrode layer 14, thereby changing the capacitance value of the strain detection capacitor. Through this value, the displacement data of the sensitive film can be obtained, and then the processing circuit can form a feedback circuit with the driving electrode to achieve more precise control and measurement. In addition, this displacement detection-control feedback circuit can reduce many undesirable film deformations, such as film deformation caused by zero drift, temperature drift and external impact, which further improves the overload resistance and zero bias performance of the device. Second, the strain detection electrode corresponding to the position of the piezoresistor 2 can be designed, and the resistance value change caused by the deformation of the piezoresistor 2 can be calculated through a corresponding algorithm, thereby further improving the measurement accuracy.

In an embodiment of the present invention, a method for preparing a high-frequency dynamic MEMS piezoresistive pressure sensor is also provided, comprising the following steps:

providing a first substrate 1 and a base;

preparing a pressure-sensitive thin film on the first substrate 1;

The upper surface of the base and the lower surface of the first substrate 1 are bonded by anodic bonding.

In order to further illustrate the production and realization of the high-frequency dynamic MEMS piezoresistive pressure sensor proposed by the present invention, Fig. 4 to Fig. 22 are schematic diagrams of the process formation process in the embodiment of the present invention, as shown in Fig. 4-22, the high-frequency dynamic The preparation method of the MEMS piezoresistive pressure sensor specifically includes:

Step a: As shown in Figure 4, select a 300 mm thick N-type (100) silicon wafer as the first substrate 1, and form a lightly doped B pressure layer on the first substrate 1 by photolithography and ion implantation. Sensitive resistor 2;

Step b: as shown in FIG. 5 , forming heavily B-doped ohmic contact regions 3 on both sides of the varistor 2 on the first substrate 1 through photolithography and ion implantation;

Step c: as shown in FIG. 6 , grow 100 nm of silicon oxide and 100 nm of silicon nitride on the upper surface of the first substrate 1 by LPCVD (Low Pressure Chemical Vapor Deposition) as the second a passivation layer 4 and a second passivation layer 5;

Step d: as shown in FIG. 7, etching the first passivation layer 4 and the second passivation layer 5 by photolithography and RIE (Reactive Ion Etching) to expose the ohmic contact region 3, and Through photolithography and magnetron sputtering a layer of copper with a thickness of 100nm-300nm, a pressure-sensitive electrode layer 6 is formed on the upper surface of the ohmic contact area 3 and the second passivation layer 5, so that the four pressure-sensitive Resistor 2 is connected to form a Wheatstone bridge;

Step e: as shown in FIG. 8 , grow a layer of silicon oxide with a thickness of 2 μm on the upper surface of the second passivation layer 5 and the pressure-sensitive electrode layer 6 by photolithography and low-pressure chemical vapor deposition method LPCVD to as the third passivation layer 7;

Step f: as shown in FIG. 9 , sputter a layer of copper with a thickness of 100 nm on the upper surface of the third passivation layer 7 by photolithography and magnetron sputtering, as the first driving electrode layer 8;

Step g: as shown in FIG. 10 , grow a layer of hafnium-zirconium with a thickness of 50-150 nm on the upper surface of the third passivation layer 7 and the first driving electrode layer 8 by ALD (Atomic Layer Deposition, atomic layer deposition) composite oxide (Hf-Zr-O), as the first dielectric layer 9;

Step h: As shown in FIG. 11 , a layer of copper with a thickness of 100 nm is sputtered on the upper surface of the first dielectric layer 9 by photolithography and magnetron sputtering as the second driving electrode layer 10;

Step i: as shown in FIG. 12 , grow a layer of silicon oxide with a thickness of 2um on the upper surfaces of the first dielectric layer 9 and the second driving electrode layer 10 by low pressure chemical vapor deposition method LPCVD as the fourth passivation layer. Layer 11;

Step j: as shown in FIG. 13 , by photolithography and ICP (Inductively Coupled Plasma, inductively coupled plasma etching), etch a first groove 12 with a depth of 270um on the back surface of the first substrate 1;

Step k: As shown in FIG. 14 , grow a layer of silicon oxide with a thickness of 1 μm on the lower surface of the first groove 12 by photolithography and low pressure chemical vapor deposition method LPCVD as the fifth passivation layer 13 ;

Step 1: As shown in FIG. 15, a layer of copper with a thickness of 100 nm is sputtered on the lower surface of the fifth passivation layer 13 by photolithography and magnetron sputtering as the first strained electrode layer 14;

Step m: As shown in FIG. 16 , grow a layer of hafnium-zirconium composite oxide with a thickness of 50 nm on the lower surface of the first strained electrode layer 14 as the second dielectric layer 15 by photolithography and atomic layer deposition ALD;

Step n: as shown in FIG. 17 , by photolithography and inductively coupled plasma etching ICP, etch a second groove 16 with a depth of 258um on the back surface of the first substrate 1, the second groove The cross-sectional area of 16 is larger than that of the first groove 12;

Step o: As shown in FIG. 18, take another piece of glass sheet with a thickness of 300um, and use photolithography and inductively coupled plasma etching ICP to obtain a ladder structure as the second substrate 17, wherein the second substrate 17 The size of the middle part is slightly smaller than the size of the first groove 12, and the height of the middle part of the second substrate 17 is 258um higher than that of the edge part;

Step p: as shown in FIG. 19 , grow a layer of silicon nitride with a thickness of 1 μm on the upper surface of the thicker middle part of the second substrate 17 by photolithography and low-pressure chemical vapor deposition method LPCVD, as the sixth passivation layer 18;

Step q: As shown in FIG. 20 , by photolithography and magnetron sputtering, a layer of copper with a thickness of 100 nm is sputtered on the upper surface of the sixth passivation layer 18 as the second strained electrode layer 19 ;

Step r: as shown in FIG. 21 , grow a layer of hafnium-zirconium composite oxide with a thickness of 50nm-100nm on the upper surface of the sixth passivation layer 18 and the second strained electrode layer 19 by photolithography and atomic layer deposition ALD , as the third dielectric layer 20;

Step s: As shown in FIG. 22 , the first substrate 1 and the second substrate 17 are bonded by anodic bonding to complete the preparation of the high-frequency dynamic MEMS piezoresistive pressure sensor.

It can be understood that, the above embodiments are only exemplary embodiments adopted for illustrating the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (9)

1. A high-frequency dynamic MEMS piezoresistive pressure sensor, characterized in that it includes a base, a first substrate (1) and a pressure-sensitive film, and the pressure-sensitive film is arranged on the first substrate (1) , the first substrate (1) is disposed on the base; Wherein, the pressure-sensitive thin film includes a piezoresistor (2), an ohmic contact area (3), a first passivation layer (4), a second passivation layer (5), a pressure-sensitive electrode layer (6), a third Passivation layer (7), first driving electrode layer (8), first dielectric layer (9), second driving electrode layer (10), fourth passivation layer (11), fifth passivation layer (13 ), a first strain electrode layer (14) and a second dielectric layer (15), the first substrate (1) is provided with four varistors (2) and eight ohmic contact regions (3), The eight ohmic contact areas (3) are respectively located at both ends of the short sides of the four varistors (2), and the first substrate (1) and the upper surface of the varistors (2) form There is the first passivation layer (4), the second passivation layer (5) is formed on the upper surface of the first passivation layer (4), and the first passivation layer (4) and the second A hole is opened on the second passivation layer (5) corresponding to the ohmic contact area (3) to expose the ohmic contact area (3), and a layer of copper is deposited on the ohmic contact area by photolithography and magnetron sputtering (3) and the upper surface of the second passivation layer (5) form the pressure-sensitive electrode layer (6), so as to connect the four piezoresistors (2) into a Wheatstone bridge, and the first The upper surface of the second passivation layer (5) and the pressure-sensitive electrode layer (6) is formed with the third passivation layer (7), and the upper surface of the third passivation layer (7) is formed with the first The driving electrode layer (8), the third passivation layer (7) and the upper surface of the first driving electrode layer (8) are formed with the first dielectric layer (9), and the first dielectric layer ( 9) is formed with the second driving electrode layer (10), and the upper surfaces of the first dielectric layer (9) and the second driving electrode layer (10) are formed with the fourth passivation layer ( 11), the back surface of the first substrate (1) is sequentially provided with a first groove (12) and a second groove (16), and the lower surface of the first groove (12) is sequentially formed with the a fifth passivation layer (13), said first strained electrode layer (14) and said second dielectric layer (15); Wherein, the base includes a second substrate (17), a sixth passivation layer (18), a second strained electrode layer (19) and a third dielectric layer (20), and the second substrate (17) The sixth passivation layer (18) is formed on the upper surface of the central part, the second strain electrode layer (19) is formed on the upper surface of the sixth passivation layer (18), and the sixth passivation layer (18) is formed on the upper surface of the sixth passivation layer (18). layer (18) and the upper surface of the second strained electrode layer (19) are formed with the third dielectric layer (20), the first substrate (1) and the second substrate (17) through the anode Bonding to form a connection, the central part of the second substrate (17), the sixth passivation layer (18), the second strained electrode layer (19) and the third dielectric layer (20) are all located in the second concave slot (16). 2. The high-frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, characterized in that the material of the first substrate (1) is monocrystalline silicon with a thickness of 50-300 μm; the piezoresistor The material of (2) is silicon lightly doped with B; the material of the eight ohmic contact regions (3) is silicon heavily doped with B; the material of the first passivation layer (4) is silicon dioxide, The thickness is 100nm-1μm; the material of the second passivation layer (5) is silicon nitride, with a thickness of 100nm-1um; the material of the pressure-sensitive electrode layer (6) is copper, with a thickness of 100nm-300nm; The material of the third passivation layer (7) is silicon dioxide with a thickness of 1-5um; the material of the first driving electrode layer (8) is metal with a thickness of 50nm-200nm; the first dielectric layer The material of (9) is a material with a high dielectric constant, with a thickness of 50-150nm; the material of the second driving electrode layer (10) is metal, with a thickness of 50nm-200nm; the fourth passivation layer (11 ) is silicon dioxide with a thickness of 1-5um; the material of the fifth passivation layer (13) is silicon dioxide with a thickness of 1-6um; the material of the first strain electrode layer (14) is The metal has a thickness of 50-200nm; the material of the second dielectric layer (15) is a material with a high dielectric constant and the thickness is 50-200nm. 3. The high-frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, characterized in that, the first driving electrode layer (8), the first dielectric layer (9) and the second driving electrode layer (10 ) constitutes the driving capacitor, which is used to provide the electrostatic force. 4. The high-frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, characterized in that, the depth of the first groove (12) is 45um-270um, and the depth of the second groove (16) is It is 43um-258um. 5. The high-frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, characterized in that, the material of the second substrate (17) is glass with a thickness of 50-300 μm; the sixth passivation layer (18) is made of silicon nitride with a thickness of 1um-6um; the material of the second strain electrode layer (19) is metal with a thickness of 50-200nm; the material of the third dielectric layer (20) is A material with a high dielectric constant, with a thickness of 50-200nm. 6 . The high-frequency dynamic MEMS piezoresistive pressure sensor according to claim 1 , characterized in that, the second strain electrode layer ( 19 ) includes a plurality of metal blocks not connected to each other, so as to measure the strain in different regions. 7. The high-frequency dynamic MEMS piezoresistive pressure sensor according to claim 1, characterized in that, the first strain electrode layer (14), the second dielectric layer (15), the third dielectric layer (20 ) and the second strain electrode layer (19) constitute the strain detection capacitance, wherein the position of the second strain electrode layer (19) remains unchanged, and the position of the first strain electrode layer (14) changes due to pressure, thereby causing capacitance The value changes to achieve the measurement of strain. 8. A preparation method of the high-frequency dynamic MEMS piezoresistive pressure sensor according to any one of claims 1-7, wherein the preparation method of the high-frequency dynamic MEMS piezoresistive pressure sensor comprises: providing a first substrate (1) and a base; preparing a pressure-sensitive thin film on the first substrate (1); The upper surface of the base and the lower surface of the first substrate (1) are bonded by anodic bonding. 9. The preparation method of high-frequency dynamic MEMS piezoresistive pressure sensor according to claim 8, is characterized in that, also comprises: Step a: Select a 300mm thick N-type (100) silicon wafer as the first substrate (1), and form a lightly doped B varistor on the first substrate (1) by photolithography and ion implantation (2); Step b: forming heavily B-doped ohmic contact regions (3) on both sides of the varistor (2) on the first substrate (1) by photolithography and ion implantation; Step c: grow 100nm silicon oxide and 100nm silicon nitride respectively on the upper surface of the first substrate (1) by low pressure chemical vapor deposition method LPCVD as the first passivation layer (4) and the second passivation layer layer(5); Step d: Etching the first passivation layer (4) and the second passivation layer (5) by photolithography and reactive ion etching (RIE) to expose the ohmic contact region (3), and performing photolithography and magnetic Controlled sputtering of a layer of copper with a thickness of 100nm-300nm to form a pressure-sensitive electrode layer (6) on the upper surface of the ohmic contact area (3) and the second passivation layer (5), so as to connect the four voltage The sensitive resistor (2) is connected into a Wheatstone bridge; Step e: growing a layer of silicon oxide with a thickness of 2um on the upper surface of the second passivation layer (5) and the pressure-sensitive electrode layer (6) by photolithography and low pressure chemical vapor deposition method LPCVD as the second Three passivation layers (7); Step f: sputtering a layer of copper with a thickness of 100 nm on the upper surface of the third passivation layer (7) by photolithography and magnetron sputtering, as the first driving electrode layer (8); Step g: growing a layer of hafnium-zirconium composite oxide with a thickness of 50-150 nm on the upper surface of the third passivation layer (7) and the first driving electrode layer (8) by atomic layer deposition ALD, as the first dielectric layer electrical layer (9); Step h: sputtering a layer of copper with a thickness of 100 nm on the upper surface of the first dielectric layer (9) by photolithography and magnetron sputtering, as the second driving electrode layer (10); Step i: growing a layer of silicon oxide with a thickness of 2um on the upper surfaces of the first dielectric layer (9) and the second driving electrode layer (10) by low-pressure chemical vapor deposition method LPCVD as the fourth passivation layer (11); Step j: Etching a first groove (12) with a depth of 270um on the back surface of the first substrate (1) by photolithography and ICP etching; Step k: growing a layer of silicon oxide with a thickness of 1um on the lower surface of the first groove (12) by photolithography and low pressure chemical vapor deposition method LPCVD, as the fifth passivation layer (13); Step 1: sputtering a layer of copper with a thickness of 100 nm on the lower surface of the fifth passivation layer (13) by photolithography and magnetron sputtering, as the first strained electrode layer (14); Step m: growing a layer of hafnium-zirconium composite oxide with a thickness of 50 nm on the lower surface of the first strained electrode layer (14) by photolithography and atomic layer deposition ALD as the second dielectric layer (15); Step n: etching the ICP by photolithography and inductively coupled plasma, etching a second groove (16) with a depth of 258um on the back surface of the first substrate (1), the second groove (16 ) has a cross-sectional area larger than the first groove (12); Step o: take another piece of glass sheet with a thickness of 300um, etch ICP by photolithography and inductively coupled plasma to obtain a ladder structure as the second substrate (17), wherein the middle part of the second substrate (17) The size is smaller than the size of the first groove (12), and the height of the middle part of the second substrate (17) is 258um higher than that of the edge part; Step p: growing a layer of silicon nitride with a thickness of 1 μm on the upper surface of the middle thicker part of the second substrate (17) by photolithography and low-pressure chemical vapor deposition method LPCVD as the sixth passivation layer ( 18); Step q: sputtering a layer of copper with a thickness of 100 nm on the upper surface of the sixth passivation layer (18) by photolithography and magnetron sputtering, as the second strained electrode layer (19); Step r: growing a layer of hafnium-zirconium composite oxide with a thickness of 50nm-100nm on the upper surface of the sixth passivation layer (18) and the second strained electrode layer (19) by photolithography and atomic layer deposition ALD, as a third dielectric layer (20); Step s: Bonding the first substrate (1) and the second substrate (17) through anodic bonding to complete the preparation of the high-frequency dynamic MEMS piezoresistive pressure sensor.