CN103196613B - A kind of high-temperature CMUT pressure sensor and preparation method thereof - Google Patents

Abstract

The invention discloses a high-temperature CMUT pressure sensor and a preparation method thereof, the overall structure of which is as follows from top to bottom: a first silicon carbide layer, a first silicon nitride layer, a second silicon carbide layer, and a second silicon nitride layer , and the third silicon carbide layer; the first silicon nitride layer, the second silicon carbide layer and the second silicon nitride layer peripheral and middle parts are separated in the lateral direction by the cavity; the through hole penetrates the third silicon carbide layer; the middle part of the second silicon nitride layer covers the upper side of the third silicon carbide layer and the inner surface of the through hole; the inner surface of the silicon nitride layer in the through hole is covered with an electrical connection metal layer and the lower electrode is formed Electrical connection; effectively reduce the impact of charging phenomenon on sensor performance; effectively reduce parasitic capacitance in high temperature environment and its impact on sensor detection sensitivity; adopt symmetrical structure design with alternating silicon carbide layers and silicon nitride layers. Effectively reduce the influence of temperature stress on sensor measurement accuracy in high temperature environment.

Description

A kind of high temperature CMUT pressure sensor and preparation method thereof

technical field

The invention belongs to the technical field of MEMS, and relates to a pressure detection device, in particular to a high-temperature CMUT pressure sensor and a preparation method thereof.

Background technique

Low-pressure detection has a wide range of application requirements in the fields of industrial control, space exploration, medical and health care, and semiconductor processing, and is an extreme challenge for pressure detection technology. At present, there are many researches on silicon micro pressure sensors based on MEMS technology, which can be mainly divided into piezoresistive, capacitive and resonant micro pressure sensors. Compared with capacitive and piezoresistive micro pressure sensors, the resonant type has more advantages; for example, the measurement accuracy, stability and resolution are better than the other two; in addition, the output of the resonant type sensor is a digital signal, which has strong anti-interference ability and is convenient for transmission. The resonant silicon micro pressure sensor can be divided into the common cantilever beam type and the micro pressure sensor based on the CMUT structure that has appeared in recent years. In addition to the common advantages of resonant pressure sensors, CMUT micro pressure sensors have a stronger and more reliable structure than cantilever beam micro pressure sensors, and are more suitable for pressure detection in harsh environments. Since the high temperature and harsh environment is one of the difficulties in the research of silicon micro pressure sensors, common micro pressure sensors mostly realize low pressure detection in conventional temperature environments (such as less than 120°C).

Since CMUT uses silicon and silicon-based compounds as the basic material, electrostatic drive as the basic driving method, and pressure-induced frequency changes to realize micro-pressure detection sensors, its application in high-temperature environments must take into account the influence of the following factors : First, the electrical and mechanical properties of common single crystal silicon and polycrystalline silicon materials deteriorate above 250°C and 600°C respectively; second, as the temperature increases, the mobility of impurity ions in the insulating layer and cavity pillars changes Larger, the parasitic capacitance of CMUT becomes larger, which will reduce the detection sensitivity; third, as the temperature rises, the charging phenomenon of the electrical insulating layer will increase, the breakdown voltage will become smaller, and the possibility of breakdown of the electrical insulating layer will increase; fourth, Due to the different thermal expansion coefficients of the structural components of the CMUT, it will cause a large temperature stress, which will lead to an increase in the error of pressure detection. Therefore, reasonable material selection and structural design are required to minimize the impact of temperature stress on sensor measurement performance. .

Contents of the invention

The purpose of the present invention is to propose a high-temperature CMUT pressure sensor and a preparation method thereof, which can effectively reduce the temperature stress in a high-temperature environment, the influence of parasitic capacitance and the charging phenomenon of an electrical insulating layer on the performance of the sensor, and realize low pressure (<10kPa) pressure in a high-temperature environment. ) detection.

To achieve the above object, the technical scheme adopted in the present invention is as follows:

A high-temperature CMUT pressure sensor whose overall structure from top to bottom is: a first silicon carbide layer, a first silicon nitride layer, a second silicon carbide layer, a second silicon nitride layer, and a third silicon carbide layer; The first silicon nitride layer, the second silicon carbide layer and the second silicon nitride layer are equally divided into a middle part and a surrounding part, and the surrounding part and the middle part are separated in the lateral direction by a cavity; the first silicon nitride layer, the second silicon carbide layer, and the surrounding parts of the second silicon nitride layer form the sidewall of the cavity, the first silicon carbide layer and the third silicon carbide layer are the top and bottom of the cavity respectively, and the cavity sidewall and the cavity The bottom and top of the cavity are sealed together; the first silicon carbide layer is ion-doped to form an upper electrode, and the middle part of the second silicon carbide layer is ion-doped to form a lower electrode; the middle part of the first silicon nitride layer is The lateral size is smaller than the lateral size of the middle part of the second silicon carbide layer, a through hole is arranged in the middle of the third silicon carbide layer, the through hole penetrates the third silicon carbide layer, and the lateral size of the through hole is smaller than the lateral size of the lower electrode; the second nitrogen The middle part of the silicon carbide layer covers the upper side of the third silicon carbide layer and the inner surface of the through hole; the inner surface of the silicon nitride layer in the through hole is covered with an electrically connected metal layer, which is electrically connected to the top of the metal layer and the lower electrode to form an electrical connection. Connection; the material of the first silicon carbide layer, the second silicon carbide layer and the third silicon carbide layer can be changed to diamond, and the material of the first silicon nitride layer and the second silicon nitride layer can be changed to silicon dioxide.

The thickness of the middle part of the first silicon nitride layer is smaller than the thickness of the surrounding part of the first silicon nitride layer.

The central point of the middle part of the first silicon nitride layer corresponds to the central point of the first silicon carbide layer.

The lateral dimension of the surrounding part of the second silicon nitride layer is the same as that of the surrounding part of the first silicon nitride layer, and is symmetrically distributed on both sides of the second silicon carbide layer.

The middle part of the second silicon nitride layer is ring-shaped, and its outer lateral dimension is smaller than that of the lower electrode.

The middle part of the first silicon nitride layer, the middle part of the second silicon carbide layer, the middle part of the second silicon nitride layer, the through hole and the metal electrical connection layer are symmetrical about the same central axis.

The first and second silicon carbide layers can be replaced with corresponding diamond layers or other similar materials, and the silicon nitride layer can be replaced with corresponding silicon dioxide layers or other similar materials.

A preparation method for a high-temperature CMUT pressure sensor, comprising the following steps:

(1) Take a P or N-type silicon carbide wafer, and use deep reactive ion etching technology to etch a through hole in the middle of the silicon carbide, the through hole runs through the silicon carbide wafer, and at this time, a third silicon carbide layer is formed;

(2) Deposit a silicon nitride layer on the upper surface of the third silicon carbide layer and the inner surface of the through hole in the middle; at the same time, take a single crystal silicon or polycrystalline silicon wafer as the first substrate silicon, and deposit a silicon carbide layer on its upper surface;

(3) Photolithography and etching the silicon nitride layer on the upper surface of the third silicon carbide layer to form a second silicon nitride layer, which is divided into a surrounding part and a middle part, and the middle part is to cover the upper surface of the third silicon nitride layer The middle part and the entire inner surface of the through hole; the middle area of the silicon carbide layer on the upper surface of the first substrate silicon is metallized by local doping technology; the second silicon nitride layer and the silicon carbide layer on the first substrate silicon are polished by chemical mechanical polishing technology The upper surface of the silicon carbide layer;

(4) Bond the second silicon nitride layer on the upper surface of the third silicon carbide layer with the silicon carbide layer on the first substrate silicon, wherein the silicon carbide layer on the first substrate silicon is on top, and the second silicon nitride layer is The silicon layer is underneath;

(5) Etching away the first substrate silicon, releasing the silicon carbide layer on the first substrate silicon, and polishing its surface by chemical mechanical polishing technology;

(6) depositing a silicon nitride layer on the silicon carbide layer derived from the first substrate silicon;

(7) Second photolithography and etching of the silicon nitride layer on the silicon carbide layer derived from the first substrate silicon to form the first silicon nitride layer, the middle part of which is a smaller area, and the thickness is smaller than that of the surrounding The thickness of part of the silicon nitride layer, the lateral dimension of the surrounding part of the silicon nitride layer is the same as the lateral dimension of the surrounding part of the second silicon nitride; at the same time, another single crystal silicon or polycrystalline silicon wafer is taken as the second substrate silicon, on which A silicon carbide layer is deposited on the surface;

(8) Photolithography and etching of the silicon carbide layer derived from the first substrate silicon to form a second silicon carbide layer, in which the central region is an electrode, and the surrounding part is undoped silicon carbide; ion doping technology is used to dope Doping the silicon carbide layer on the second substrate silicon to form the first silicon carbide layer;

(9) Using chemical mechanical polishing technology to polish the upper surfaces of the first silicon carbide layer and the first silicon nitride layer, and vacuum bonding the two, wherein the first silicon carbide layer is on the top and the first silicon nitride layer is on the bottom. When the first silicon nitride layer, the second silicon carbide layer and the surrounding part of the second silicon nitride layer form the side wall of the cavity, the first silicon carbide layer and the third silicon carbide layer are respectively the top and bottom of the cavity, and the side wall Seal the cavity together with the top and bottom;

(10) Etch away the second substrate silicon used to deposit the first silicon carbide layer, release the first silicon carbide layer, and at the same time sputter a high-temperature resistant metal layer on the inner surface of the silicon nitride layer in the through hole, the top of the metal layer An electrical connection is formed with the middle region of the second silicon carbide layer, and the side wall of the metal layer covers the inner wall of the silicon nitride layer in the through hole.

The high temperature resistant metal layer sputtered in the through hole in step (10) is a nickel layer or a manganese layer.

The high-temperature CMUT pressure sensor of the present invention and its preparation method have at least the following advantages:

(1) In the conventional CMUT structure, because the electrical insulating layer covers the entire upper surface of the lower electrode, when the upper and the electrodes form a strong electric field, a charge layer appears on the surface of the electrical insulating layer or its interface with the lower electrode or inside the electrical insulating layer. That is, the charging phenomenon of the electrical insulating layer, which will affect the DC bias voltage operating point and working performance of the CMUT; and the lateral dimension of the electrical insulating layer in the present invention is much smaller than the lateral dimension of the lower electrode, effectively reducing the impact of the charging phenomenon on the working performance of the sensor .

(2) In the conventional CMUT structure, since the entire single crystal silicon substrate is used as the lower electrode or the metal electrode layer covers the entire substrate as the lower electrode, the side wall of the cavity between the lower electrode and the upper electrode forms a parasitic capacitance, and at high temperature Due to the enhanced conductivity of single crystal silicon or polycrystalline silicon material, the parasitic capacitance becomes larger. In the present invention, however, the lower electrode is located inside the cavity, and is completely electrically isolated from the sidewall and the third silicon carbide layer, effectively reducing the parasitic capacitance in a high-temperature environment and its influence on the detection sensitivity of the sensor.

(3) The present invention adopts a symmetrical structure design in which silicon carbide layers and silicon nitride layers alternate, which can effectively reduce the influence of temperature stress on sensor measurement accuracy in a high temperature environment.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a flow chart of the preparation method of the present invention;

The symbols in the figure are specifically indicated as follows:

detailed description

The present invention is described in detail below in conjunction with accompanying drawing:

As shown in Figure 1, the overall structure of the present invention is as follows from top to bottom: the first silicon carbide layer 1, the first silicon nitride layer 4, the second silicon carbide layer 2, the second silicon nitride layer 5, the third Silicon carbide layer 3. The first silicon nitride layer 4 , the second silicon carbide layer 2 , and the second silicon nitride layer 5 are equally divided into a peripheral portion and a middle portion, and the peripheral portion and the middle portion are separated by a cavity 14 in the lateral direction. The surrounding parts of the first silicon nitride layer 4, the second silicon carbide layer 2, and the second silicon nitride layer 5 form the side walls of the cavity 14, and the first silicon carbide layer 1 and the third silicon carbide layer 3 are respectively cavities. The top and bottom of the cavity 14 seal the cavity together with the first silicon carbide layer 1 and the third silicon carbide layer 3 . The material of the first, second, and third silicon carbide layers 1, 2, and 3 can be replaced by diamond or other similar materials, and the first and second silicon nitride layers 4, 5 can be replaced by silicon dioxide or other similar materials. Material.

The first silicon carbide layer 1 is a pressure sensitive element, which is used as an upper electrode after ion doping or partial ion doping. The lateral dimension of the upper electrode should be based on the principle of reducing the collapse voltage and increasing the electromechanical coupling efficiency. The size of the first silicon carbide layer 1 should comprehensively consider factors such as electrode conductivity, CMUT operating frequency, and pressure detection sensitivity.

The second silicon carbide layer 2 can be divided into a middle part 7 and a surrounding part 6, the middle part 7 is used as a lower electrode after ion doping, the surrounding part 6 is an undoped silicon carbide layer, the middle part 7 and the surrounding Parts 6 are separated by cavities 14 in the lateral direction, realizing electrical isolation between middle part 7 and surrounding parts 6, avoiding parasitic capacitance caused by surrounding parts 6 in high temperature environment. The size of the middle part 7 of the second silicon carbide layer 2 should be designed based on good electrical conductivity and greater electromechanical coupling performance. The thickness of the second silicon carbide layer 2 should be designed on the principle of maintaining good stress matching and structural shape stability.

The first silicon nitride layer 4 is divided into a middle part 11 and a surrounding part 10, the middle part 11 and the surrounding part 10 are separated by a cavity 14, the thickness of the middle part 11 is smaller than the thickness of the surrounding part 10, and the surrounding part 10 The thickness of the first silicon carbide layer 1 determines the effective electrode distance between the upper electrode and the lower electrode 7, and the thickness of the middle part 11 determines the maximum displacement of the center point of the first silicon carbide layer 1. The center point of the middle part 11 of the first silicon nitride layer corresponds to the center point of the first silicon carbide layer 1, which is used to prevent the electrical contact between the upper electrode and the lower electrode 7 in the first silicon carbide layer 1; the first The lateral size of the middle part 11 of the silicon nitride layer 4 is much smaller than the lateral size of the middle part 7 of the second silicon carbide layer, ideally an insulating point, so as to minimize the influence of the charging phenomenon of the middle part 11 on the working performance of the sensor.

The third silicon carbide layer 3 is divided into two parts, the middle through hole 9 and the silicon carbide bottom plate 8, wherein the through hole 9 runs through the third silicon carbide layer 3 in the thickness direction in order to realize the electrical connection of the lower electrode 7, and the through hole 9 The lateral dimension should be smaller than that of the lower electrode 7, and the thickness of the silicon carbide base plate 8 should ensure the stability of the structure in temperature changes.

The second silicon nitride layer 5 is divided into a middle part 12 and a surrounding part 13. The middle part 12 covers the middle part of the silicon carbide bottom plate 8 and the inner surface of the through hole 9, and is used to realize the bottom plate 8 and the lower electrode 7 and the electric circuit. Electrical insulation between the metal layers 15 is connected. The lateral dimension of the surrounding portion 13 of the second silicon nitride layer is the same as that of the surrounding portion 10 of the first silicon nitride layer, and is symmetrically distributed on both sides of the second silicon nitride layer 6, so as to realize the symmetry of thermal stress, Minimize the structural deformation of the CMUT in the temperature environment. The thickness dimension of the second silicon nitride layer 5 should ensure good insulation performance and be as small as possible. The middle part 12 of the second silicon nitride layer located on the upper side of the bottom plate 8 is ring-shaped, and its internal lateral dimension is the size of the through hole 9 minus the thickness of the silicon nitride layer on the inner surface of the through hole 9, and the external lateral dimension should be as small as possible. The lateral dimension of the electrode 7 is to reduce the influence of the thermal stress mismatch between the lower electrode 7 and the middle part 12 of the second silicon nitride layer on the shape of the lower electrode 7, and at the same time ensure a good connection between the lower electrode 7 and the silicon carbide base plate 8 strength.

The electrical connection metal layer 15 covers the inner surface of the silicon nitride layer on the through hole 9, and its top forms an electrical connection with the lower electrode 7. The thickness of the metal layer 15 comprehensively considers three factors of electrical connection performance, resistance and thermal stress.

The surrounding parts 10, 6, 13 of the first silicon nitride layer 4, the second silicon carbide layer 2 and the second silicon nitride layer 5 together form the sidewall of the cavity 14, the first silicon carbide layer 1 and the third silicon carbide layer 1 The silicon carbide layer 3 serves as the top and bottom of the cavity, and the side walls together with the top and bottom seal the cavity 14 .

The cavity 14 not only includes the space between the first silicon carbide layer 1 and the lower electrode 7, but also includes between the lower electrode 7 and the surrounding part 6 of the second silicon carbide layer, the third silicon carbide layer 13 and the second nitrogen The space portion between the middle portion 12 of the SiO layer.

The middle part 11 of the first silicon nitride layer, the middle part 7 of the second silicon carbide layer, the middle part 12 of the second silicon nitride layer, the through hole 9 and the metal electrical connection layer 15 are symmetrical about the same central axis.

As shown in Figure 2, the preparation method of the present invention is described:

(1) Take a P or N-type silicon carbide wafer, and use deep reactive ion etching technology to etch a through hole 9 in the middle of the silicon carbide, and the through hole 9 runs through the silicon carbide wafer in the thickness direction. At this time, a third silicon carbide wafer is formed. Silicon carbide layer 3;

(2) Deposit a silicon nitride layer 16 on the upper surface of the third silicon carbide layer 3 and the inner surface of the through hole 9 in the middle; at the same time, take a single crystal silicon or polycrystalline silicon wafer as the first substrate silicon 17, and deposit carbonized silicon on its upper surface. Silicon layer 18;

(3) photolithography, etching silicon nitride layer 16 forms the second silicon nitride layer 5, and it is divided into peripheral part 13 and middle part 12, and middle part is to cover the middle part of the upper surface of the third silicon nitride layer 3 and the whole The inner surface part of the through hole 9; the middle area of the silicon carbide layer 18 on the upper surface of the first substrate silicon 17 is metallized by local doping technology, and this area will be used as the middle part 7 of the second silicon carbide layer in the future, that is, the lower electrode; Polishing the upper surface of the second silicon nitride layer 5 and the upper surface of the silicon carbide layer 19 on the first substrate silicon 17 by chemical mechanical polishing technology;

(4) bonding the second silicon nitride layer 5 to the silicon carbide layer 19, wherein the silicon carbide layer 19 is on top and the second silicon nitride layer 5 is on the bottom;

(5) Etching away the first substrate silicon 17, releasing the silicon carbide layer 19 on the first substrate silicon, and polishing its surface by chemical mechanical polishing technology;

(6) depositing a silicon nitride layer 20 on the silicon carbide layer 19;

(7) Second photolithography, etching silicon nitride layer 20 to form the first silicon nitride layer 4, the middle part 11 is a small area, and the thickness is smaller than the silicon nitride layer 10 of the surrounding part, and the surrounding part is nitrided The lateral dimension of the silicon layer 10 is the same as the lateral dimension of the second silicon nitride peripheral part 13; at the same time, another single crystal silicon or polycrystalline silicon wafer is taken as the second substrate silicon 21, and a silicon carbide layer 22 is deposited on its upper surface;

(8) Photolithography and etching the silicon carbide layer 19 to form the second silicon carbide layer 2, the middle region 7 is an electrode, and the surrounding part 6 is undoped silicon carbide; the second lining is doped by ion doping technology A silicon carbide layer 22 on the bottom 21 to form a first silicon carbide layer 1;

(9) The upper surfaces of the first silicon carbide layer 1 and the first silicon nitride layer 4 are polished by chemical mechanical polishing technology, and the two are vacuum bonded, wherein the first silicon carbide layer 1 is on top, and the first silicon nitride layer 4 on the bottom, at this time the first silicon nitride layer 4, the second silicon carbide layer 2 and the surrounding parts 10, 6, 13 of the second silicon nitride layer 5 form the side walls of the cavity, the first silicon carbide layer 1 and the third silicon carbide layer The silicon carbide layer 3 is the top and the bottom of the cavity 14 respectively, and the side walls together with the top and the bottom seal the cavity 14;

(10) Etch away the second substrate silicon 21 to release the first silicon carbide layer 1; sputter nickel or manganese-resistant layer 15 on the inner surface of the silicon nitride layer in the through hole 9, and the top of the metal layer and the second silicon carbide layer The middle region 7 of the layer 2 forms an electrical connection, and the sidewall of the metal layer covers the inner wall of the silicon nitride layer in the through hole 9 .

In combination with the above embodiments, the reference structural parameters of the high temperature CMUT pressure sensor of the present invention are:

The effective lateral size of the first silicon carbide layer (the part of the silicon carbide layer that can vibrate): 16-200 μm

Cavity height: 0.4～10μm

The maximum lateral size of the cavity: 16 ~ 200μm

Effective lateral dimension of the lower electrode: 16-200μm

The reference performance index of the high temperature CMUT pressure sensor of the present invention is:

Measurement sensitivity: magnitude (10Hz/Pa～100Hz/Pa).

Applicable temperature range: 200～400℃.

The present invention is not limited to the above-described embodiments. The shape and size of the film of the CMUT structure, the shape and size of the electrode, the size of the cavity, and the high-temperature materials used can be determined according to specific performance requirements to improve the reliability of the CMUT pressure sensor. , sensitivity, and at the same time reduce the influence of temperature stress, parasitic capacitance and the charging phenomenon of the electrical insulation layer between electrodes on the performance of the design and optimization.

Claims (9)

1. A high-temperature CMUT pressure sensor, characterized in that: its overall structure from top to bottom is: the first silicon carbide layer (1), the first silicon nitride layer (4), the second silicon carbide layer (2) , the second silicon nitride layer (5), and the third silicon carbide layer (3); the first silicon nitride layer (4), the second silicon carbide layer (2) and the second silicon nitride layer (5) are all Divided into a middle part and a surrounding part, and the surrounding part and the middle part are separated in the lateral direction by a cavity (14); the first silicon nitride layer (4), the second silicon carbide layer (2), the second nitrogen The surrounding part of the silicon carbide layer (5) forms the sidewall of the cavity (14), the first silicon carbide layer (1) and the third silicon carbide layer (3) are respectively the top and the bottom of the cavity, and the cavity sidewall and The bottom and top of the cavity seal the cavity (14); the first silicon carbide layer (1) is ion-doped to form an upper electrode, and the middle part (7) of the second silicon carbide layer is ion-doped to form a lower electrode; the first The lateral size of the middle part (11) of the silicon nitride layer is much smaller than the lateral size of the middle part (7) of the second silicon carbide layer, and a through hole (9) is arranged in the middle of the third silicon carbide layer (3), and the through hole (9) Through the third silicon carbide layer (3), the lateral dimension of the through hole (9) is smaller than the lateral dimension of the lower electrode; the middle part (12) of the second silicon nitride layer covers the upper side of the third silicon carbide layer (3) and the through hole The inner surface of (9); the inner surface of the silicon nitride layer in the through hole (9) is covered with a lower electrode electrically connected to the metal layer (15), and the lower electrode is electrically connected to the top of the metal layer (15) to form an electrical connection with the lower electrode . 2. The high-temperature CMUT pressure sensor according to claim 1, characterized in that: the materials of the first silicon carbide layer (1), the second silicon carbide layer (2) and the third silicon carbide layer (3) are replaced by For diamond, the materials of the first silicon nitride layer (4) and the second silicon nitride layer (5) are replaced by silicon dioxide. 3. The high temperature CMUT pressure sensor according to claim 1 or 2, characterized in that the thickness of the middle part (11) of the first silicon nitride layer is smaller than the thickness of the surrounding part (10) of the first silicon nitride layer. 4. The high-temperature CMUT pressure sensor according to claim 1 or 2, characterized in that: the center point of the middle part (11) of the first silicon nitride layer corresponds to the center point of the first silicon carbide layer (1). 5. The high-temperature CMUT pressure sensor according to claim 1 or 2, characterized in that: the lateral dimension of the surrounding portion (13) of the second silicon nitride layer is the same as the lateral dimension of the surrounding portion (10) of the first silicon nitride layer , and symmetrically distributed on both sides of the second silicon carbide layer (2). 6. The high-temperature CMUT pressure sensor according to claim 1 or 2, characterized in that: the middle part (12) of the second silicon nitride layer is ring-shaped, and its outer lateral dimension is smaller than that of the lower electrode. 7. The high-temperature CMUT pressure sensor according to claim 1 or 2, characterized in that: the middle part (11) of the first silicon nitride layer, the middle part (7) of the second silicon carbide layer, the middle part of the second silicon nitride layer The part (12), the through hole (9), and the lower electrode metal electrical connection layer (15) are symmetrical about the same central axis. 8. A method for preparing a high-temperature CMUT pressure sensor, comprising the following steps: (1) Take a P-type or N-type silicon carbide wafer, use deep reactive ion etching technology to etch a through hole (9) in the middle of the silicon carbide, and the through hole (9) runs through the silicon carbide wafer, forming a third Silicon carbide layer (3); (2) Deposit a silicon nitride layer (16) on the upper surface of the third silicon carbide layer (3) and the inner surface of the through hole (9) in the middle; get a single crystal silicon or polycrystalline silicon wafer as the first substrate silicon (17) simultaneously ), depositing a silicon carbide layer (18) on its upper surface; (3) Photoetching, etching the silicon nitride layer on the upper surface of the third silicon carbide layer (3) forms the second silicon nitride layer (5), which is divided into the second silicon nitride layer surrounding part (13) and the second silicon nitride layer The middle part (12) of the silicon nitride layer, the middle part (12) of the second silicon nitride layer is to cover the middle part of the upper surface of the third silicon carbide layer (3) and the inner surface part of the whole through hole (9); Metallize the middle region of the silicon carbide layer (18) on the upper surface of the first substrate silicon (17) by miscellaneous technology; use chemical mechanical polishing technology to polish the second silicon nitride layer (5) and the silicon nitride layer on the first substrate silicon (17) The upper surface of the silicon carbide layer (19); (4) Bond the second silicon nitride layer (5) on the upper surface of the third silicon carbide layer (3) with the silicon carbide layer (19) on the first substrate silicon (17), wherein the first substrate silicon The upper silicon carbide layer (19) is on top, and the second silicon nitride layer (5) is on the bottom; (5) Etching away the first substrate silicon (17), releasing the silicon carbide layer (19) on the first substrate silicon, and polishing its surface by chemical mechanical polishing technology; (6) depositing a silicon nitride layer (20) on the silicon carbide layer (18) derived from the first substrate silicon; (7) secondary photolithography, etch the silicon nitride layer (20) on the silicon carbide layer derived from the first substrate silicon, so that it forms the first silicon nitride layer (4), the first silicon nitride layer The middle part (11) is a smaller area, and the thickness is smaller than the silicon nitride layer thickness of the first silicon nitride layer surrounding part (10), and the silicon nitride layer lateral dimension of the first silicon nitride layer surrounding part (10) is the same as The lateral dimensions of the surrounding part (13) of the second silicon nitride layer are the same; at the same time, another monocrystalline silicon or polycrystalline silicon wafer is taken as the second substrate silicon (21), and a silicon carbide layer (22) is deposited on its upper surface; (8) Photolithography and etching are derived from the silicon carbide layer (19) of the first substrate silicon to form a second silicon carbide layer (2), wherein the central region (7) is an electrode, and the surrounding area of the second silicon carbide layer is The part (6) is undoped silicon carbide; the silicon carbide layer (22) on the second substrate silicon (21) is doped by ion doping technology, so that it forms the first silicon carbide layer (1); (9) Using chemical mechanical polishing technology to polish the upper surfaces of the first silicon carbide layer (1) and the first silicon nitride layer (4), and vacuum bonding the two, wherein the first silicon carbide layer (1) is on top, The first silicon nitride layer (4) is below, and at this time the first silicon nitride layer (4), the second silicon carbide layer (2) and the surrounding parts of the second silicon nitride layer (5) form a cavity (14) The side walls, the first silicon carbide layer (1) and the third silicon carbide layer (3) are respectively the top and bottom of the cavity (14), and the side walls together with the top and the bottom seal the cavity (14); (10) etch away the second substrate silicon (21) used to deposit the first silicon carbide layer (1), release the first silicon carbide layer (1), and the silicon nitride layer in the through hole (9) The inner surface is sputtered with a high-temperature-resistant metal layer to form a lower electrode electrically connected to the metal layer (15), and the lower electrode is electrically connected to the top of the metal layer (15) to form an electrical connection with the middle region of the second silicon carbide layer (2), and the side wall of the metal layer covers On the inner wall of the silicon nitride layer in the through hole (9). 9. The method for preparing a high temperature CMUT pressure sensor according to claim 8, characterized in that: the high temperature resistant metal layer sputtered in the through hole (9) in the step (10) is a nickel layer or a manganese layer.