MEMS pressure sensor and preparation method thereof

Abstract

The invention relates to an MEMS pressure sensor and a preparation method thereof, and belongs to the technical field of micromachining. The sensor comprises a substrate, a silicon wafer cup-shaped structure layer which is arranged on the surface of one side of the substrate and provided with a cavity, a first insulating layer and a buffer layer which is arranged on the surface of the side, away from the substrate, of the first insulating layer, and the buffer layer comprises a first buffer layer and a second buffer layer which are arranged in a stacked mode and are made of different materials. The first buffer layer is a magnesium oxide buffer layer, and the second buffer layer is an aluminum nitride buffer layer. The first buffer layer and the second buffer layer improve the electrical performance of the device by improving the thermal stability of the sensor, and the electrical performance, the stability and the reliability of the MEMS pressure sensor are integrally improved.

Description

Technical Field

[0001] This application relates to the field of microfabrication technology, and more particularly to a MEMS pressure sensor and a method for manufacturing the same. Background Art

[0002] Micro-Electro-Mechanical System (MEMS) is developed on the basis of semiconductor manufacturing technology, and is a high-tech electromechanical device fabricated by integrating technologies such as lithography, etching, thin film, silicon micromachining, non-silicon micromachining, and precision machining.

[0003] Sensors play an important role in life as an effective means of collecting information.

[0004] MEMS pressure sensors are widely used in fields such as automotive, medical, and aerospace. However, existing MEMS pressure sensors still need to be improved. Summary of the Invention

[0005] This application aims to solve at least one of the technical problems existing in the prior art. For this purpose, this application provides a MEMS pressure sensor and a method for manufacturing the same. The MEMS pressure sensor has good thermal stability and excellent electrical properties, which is beneficial to ensuring the high-sensitivity operation of the sensor.

[0006] The first aspect of this application is to provide a MEMS pressure sensor, which includes:

[0007] A substrate;

[0008] A silicon wafer cup-shaped structure layer: disposed on one side surface of the above-mentioned substrate; a cavity is formed on the side of the silicon wafer cup-shaped structure layer facing the above-mentioned substrate; an ion implantation block doping layer is formed on the surface layer of the silicon wafer cup-shaped structure layer facing away from the above-mentioned substrate;

[0009] A first insulating layer: covering the above-mentioned ion implantation block doping layer, and the first insulating layer is provided with a first through hole for exposing a part of the upper surface of the above-mentioned ion implantation block doping layer;

[0010] A buffer layer: disposed on the side surface of the first insulating layer facing away from the substrate, and the buffer layer includes a first buffer layer and a second buffer layer which are stacked and have different materials, and a second through hole communicating with the first through hole is provided on the buffer layer;

[0011] A first protective layer: disposed on the side surface of the buffer layer facing away from the substrate, and the first protective layer is provided with a third through hole communicating with the second through hole;

[0012] A metal layer: filling the first through hole, the second through hole, and the third through hole;

[0013] Second insulating layer: disposed on the surface of the first protective layer facing away from the substrate, and exposing a part of the upper surface of the metal layer;

[0014] Second protective layer: disposed on the surface of the second insulating layer facing away from the substrate.

[0015] In some embodiments, the second buffer layer includes any one or more of an aluminum nitride buffer layer, a scandium-doped aluminum nitride buffer layer, a lead zirconate titanate buffer layer, a sodium potassium niobate buffer layer, and a lead magnesium niobate buffer layer;

[0016] The first buffer layer includes a magnesium oxide buffer layer;

[0017] The first buffer layer is disposed in contact with the first insulating layer, and the second buffer layer is disposed in contact with the first protective layer.

[0018] In some embodiments, the ratio of the thickness of the first buffer layer to the thickness of the second buffer layer is (0.5 - 1):1.

[0019] In some embodiments, the thickness of the buffer layer is 1000 angstroms to 3000 angstroms.

[0020] In some embodiments, the orthographic projection of the cavity on the silicon wafer cup-shaped structure layer completely overlaps with a part of the ion implantation block doping layer.

[0021] In some embodiments, the cavity includes an open end facing the substrate and a bottom end opposite to the open end. The distance between the open end and the bottom end is h1, and h1 is 350 μm to 390 μm; the thickness of the silicon wafer cup-shaped structure layer is H, and H is 360 μm to 400 μm.

[0022] The second aspect of the present application is to provide a method for manufacturing the MEMS pressure sensor described in the first aspect. The manufacturing method includes the following manufacturing processes:

[0023] Provide a silicon wafer;

[0024] Form an ion implantation block doping layer on one side surface layer of the silicon wafer;

[0025] Grow a first insulating layer, a first buffer layer, a second buffer layer, and a first protective layer in sequence on one side of the ion implantation block doping layer;

[0026] Etch the first insulating layer, the buffer layer, and the first protective layer to obtain a connected first through hole, second through hole, and third through hole;

[0027] Grow a metal layer on the first protective layer and fill the third through hole, the second through hole, and the first through hole;

[0028] Partially etching the metal layer, growing a second insulating layer and a second protective layer on the etched metal layer, and etching the second insulating layer and the second protective layer to expose a portion of the upper surface of the metal layer;

[0029] Etching a groove in the central area of the silicon wafer away from the doping layer of the ion implantation block;

[0030] The silicon wafer with the groove is combined with the substrate through a bonding process to form a cavity.

[0031] In some embodiments, the growth of the first buffer layer is performed by atomic layer deposition, and the deposition step includes:

[0032] The surface on which the first buffer layer is to be deposited is heated to 150° C. to 350° C.;

[0033] Introducing a magnesium precursor onto the surface of the first buffer layer to be deposited, and controlling the pulse time to be 0.1s to 2.0s;

[0034] Introducing an oxidant to the surface of the first buffer layer to be deposited, and controlling the pulse time to be 0.1s to 2.0s;

[0035] The above deposition process is regarded as one cycle, and the cycle is repeated multiple times.

[0036] In some embodiments, the magnesium precursor is a cyclopentadienyl compound of magnesium;

[0037] The above oxidant is ozone.

[0038] In some embodiments, the second buffer layer is grown by plasma enhanced chemical vapor deposition, and the deposition step includes:

[0039] Introducing a nitrogen precursor and an aluminum precursor to the surface of the second buffer layer to be deposited, the flow rate of the nitrogen precursor is 30 sccm to 70 sccm, the flow rate of the aluminum precursor is 3 sccm to 10 sccm, and the pressure is 80 Pa to 150 Pa;

[0040] The RF power is controlled to be 250W-350W, the deposition temperature is 240°C-360°C, and the deposition time is 2min-3min.

[0041] In some embodiments, the nitrogen precursor is hydrogen nitride, and the aluminum precursor is trimethylaluminum.

[0042] Beneficial technical effects of this application:

[0043] The MEMS pressure sensor provided in the present application has the characteristics of good thermal stability and excellent electrical performance, which is conducive to improving the electrical performance and reliability of the entire sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Upon reading the following detailed description of the preferred embodiments, various other advantages and benefits will become apparent to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present application. Moreover, throughout the drawings, the same reference numerals are used to denote the same components. In the drawings:

[0045] Figure 1 is a process flow diagram of the preparation of a MEMS pressure sensor schematically shown in some embodiments of the present application;

[0046] Figure 2 is a schematic structural diagram of a MEMS pressure sensor schematically shown in some embodiments of the present application;

[0047] Figures 3A to 3I is Figure 2 a schematic structural diagram of the preparation process of the MEMS pressure sensor schematically shown.

[0048] The component numbers in the above drawings are as follows:

[0049] 1000, MEMS pressure sensor;

[0050] 1001, substrate;

[0051] 1002, silicon wafer cup-like structure layer; 1002a, cavity; 1002b, first ion implantation block doping layer; 1002c, second ion implantation block doping layer; 1002d, third ion implantation block doping layer; 1002’, silicon wafer;

[0052] 1003, first insulating layer;

[0053] 1004, buffer layer; 1004a, first buffer layer; 1004b, second buffer layer;

[0054] 1005, first protective layer;

[0055] 1006, metal layer;

[0056] 1007, phosphorus-doped polysilicon layer;

[0057] 1008, second insulating layer;

[0058] 1009, second protective layer. Detailed Embodiments

[0059] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application will be further described below with reference to the accompanying drawings and specific embodiments. The implementation modes in the present application can be implemented in multiple different forms. It is easy for those of ordinary skill in the art to understand the fact that the implementation modes and contents can be transformed into various forms without departing from the gist and scope of the present application. Therefore, the present application should not be construed as being limited only to the contents described in the following implementation modes. Without conflict, the embodiments and features in the embodiments of the present application can be arbitrarily combined with each other.

[0060] Structural diagrams according to embodiments of the present application are shown in the accompanying drawings. The drawing ratios can be used as a reference in actual processes, but are not limited thereto. For example, the width-to-length ratio of the channel, the thickness and spacing of each film layer, and the width and spacing of each signal line can be adjusted according to actual needs. The number of pixels in the display substrate and the number of sub-pixels in each pixel are not limited to the numbers shown in the figures. The accompanying drawings described in the present application are only structural diagrams, and one implementation mode of the present application is not limited to the shapes, values, etc. shown in the accompanying drawings.

[0061] In the context of the present application, when a layer / component is referred to as being "on" another layer / component, the layer / component can be directly on the other layer / component, or there can be an intermediate layer / component therebetween. Additionally, if a layer / component is "on" another layer / component in one orientation, then when the orientation is reversed, the layer / component can be "under" the other layer / component.

[0062] In the description of the present application, ordinal numbers such as "first" and "second" are set to avoid confusion of components and are not intended to limit the quantity.

[0063] In this specification, for convenience, terms indicating orientation or positional relationships such as "middle", "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are used to describe the positional relationships of the components with reference to the accompanying drawings, which are only for facilitating the description of this specification and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application. The positional relationships of the components are appropriately changed according to the directions for describing each component. Therefore, it is not limited to the terms described in the specification and can be appropriately replaced according to the circumstances.

[0064] In this specification, unless otherwise clearly defined or limited, the terms "arranged" and "connected" shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, indirectly connected through an intermediate member, or the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0065] "A and / or B" includes the following two combinations: only A, only B, and the combination of A and B.

[0066] "At least one of A, B, and C" has the same meaning as "at least one of A, B, or C", and both include the following combinations of A, B, and C: only A, only B, only C, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B, and C.

[0067] Exemplary embodiments are described herein with reference to cross-sectional views and / or plan views that are idealized exemplary drawings. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Thus, variations in the shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Accordingly, exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include shape deviations resulting from, for example, manufacturing. For example, an etched region shown as rectangular will typically have curved features. Thus, the regions shown in the drawings are schematic in nature, and their shapes are not intended to depict the actual shape of the regions of the device, and are not intended to limit the scope of the exemplary embodiments.

[0068] Micro-Electro-Mechanical System (MEMS) is a high-tech electro-mechanical device developed on the basis of semiconductor manufacturing technology, integrating technologies such as lithography, etching, thin film, silicon microfabrication, non-silicon microfabrication, and precision machining.

[0069] Sensors play an important role in life as an effective means of collecting information. Pressure sensors are widely used in the fields of automobiles, medical treatment, aerospace, etc. Their basic principle is to convert the pressure change or deformation change value into an electrical signal. MEMS pressure sensors include piezoresistive and capacitive types. Piezoresistive pressure sensors are based on piezoresistors to effectively convert pressure signals into electrical signals, achieving accurate pressure measurement and improving measurement accuracy to a certain extent. Piezoresistive pressure sensors include silicon piezoresistive pressure sensors. Silicon piezoresistive pressure sensors are made using the piezoresistive effect of single crystal silicon. They use a circular stress cup silicon film inner wall fixed around the periphery, and directly engrave four high-precision semiconductor strain gauges at the maximum stress point on its surface to form a Wheatstone measurement bridge, which serves as a force-to-electricity conversion measurement circuit to directly convert pressure into electrical quantity and achieve pressure measurement.

[0070] However, the electrical performance of existing silicon piezoresistive pressure sensors needs to be improved. For example, the temperature stability of the sensor itself is poor, so that the sensitivity of the sensor is affected by changes in ambient temperature during use, which ultimately affects the electrical performance of the silicon piezoresistive pressure sensor.

[0071] In order to solve the above technical problems, the present application discloses a MEMS pressure sensor, which includes a substrate, a silicon wafer cup-shaped structure layer, a first insulating layer, a buffer layer, a first protective layer, a metal layer, a second insulating layer and a second protective layer; wherein the silicon wafer cup-shaped structure layer is arranged on one side surface of the substrate; a cavity is formed on the side of the silicon wafer cup-shaped structure layer facing the substrate; an ion implantation block doping layer is formed on the surface of the silicon wafer cup-shaped structure layer facing away from the substrate;

[0072] The first insulating layer covers the ion implantation block doping layer, and the first insulating layer is provided with a first through hole exposing a portion of the upper surface of the ion implantation block doping layer;

[0073] The buffer layer is disposed on a surface of the first insulating layer facing away from the substrate, and the buffer layer includes a first buffer layer and a second buffer layer which are stacked and made of different materials, and a second through hole communicating with the first through hole is disposed on the buffer layer;

[0074] The first protective layer is disposed on a surface of the buffer layer facing away from the substrate, and the first protective layer is provided with a third through hole communicating with the second through hole;

[0075] The metal layer fills the first through hole, the second through hole and the third through hole;

[0076] The second insulating layer is disposed on a surface of the first protective layer facing away from the substrate, and exposes a portion of the upper surface of the metal layer;

[0077] The second protective layer is disposed on the surface of the second insulating layer facing away from the substrate.

[0078] The silicon wafer cup-shaped structure layer of the present application includes a conventional shape in the art. For example, a cavity is formed on the side of the silicon wafer cup-shaped structure layer facing the substrate, and the cavity is used to form a stress cavity to withstand and sense pressure changes. And an ion implantation block doping layer is formed on the surface layer of the silicon wafer cup-shaped structure layer on the side facing away from the substrate. Among them, ion implantation is a doping method for the doping layer. By implanting the ions to be doped into the surface layer of the silicon wafer cup-shaped structure layer on the side facing away from the substrate, a predetermined conductivity and function are achieved, that is, it is used to make the silicon material have a controllable conductivity.

[0079] In some embodiments, the ion implantation block doping layer includes a high-concentration N-type doping region (abbreviated as N+), a high-concentration P-type doping region (abbreviated as P+), and a low-concentration P-type doping region (abbreviated as P-). Among them, N+ means implanting an N-type impurity (such as phosphorus or arsenic) into the surface layer of the silicon wafer cup-shaped structure layer on the side facing away from the substrate to form a high-concentration region. P+ means implanting a P-type impurity (such as boron) into the surface layer of the silicon wafer cup-shaped structure layer on the side facing away from the substrate to form a high-concentration region. P- means implanting a P-type impurity into the surface layer of the silicon wafer cup-shaped structure layer on the side facing away from the substrate to form a low-concentration region.

[0080] In some embodiments, the high-concentration N-type doping region (abbreviated as N+) means implanting phosphorus, and the implantation amount is a dose of 5e15 cm -2 .

[0081] In some embodiments, the high-concentration P-type doping region (abbreviated as P+) means implanting boron, and the implantation amount is a dose of 1e16 cm -2 .

[0082] In some embodiments, the low-concentration P-type doping region (abbreviated as P-) means implanting boron, and the implantation amount is a dose of 3e14 cm -2 .

[0083] The ion implantation block doping layer provided by the present application is generally used to form source and drain regions, and to create low-impedance contact points, so as to make the silicon material have a controllable conductivity.

[0084] The first insulating layer of the present application is used to reduce electrical interference inside the sensor. The second insulating layer of the present application is used to reduce the influence of the external environment on the sensor.

[0085] In the present application, the materials of the first insulating layer and the second insulating layer include silicon oxides, such as silicon dioxide.

[0086] The first protective layer and the second protective layer of the present application not only protect the sensor from external environmental interference and damage, but also ensure that the external pressure to be measured is effectively transmitted to the sensor to achieve accurate pressure detection.

[0087] The materials of the first protective layer and the second protective layer in the present application include silicon nitride, such as silicon nitride.

[0088] A buffer layer is provided between the first insulating layer and the second insulating layer in the present application. This buffer layer serves as a mechanical transition layer. Specifically, this buffer layer includes a first buffer layer and a second buffer layer with different materials, which is beneficial to improving the electrical performance of the sensor. For example, it can improve the thermal stability of the sensor, reduce the performance degradation of the sensor in a high-temperature environment, make the rate of change of the output electrical signal of the sensor with pressure become faster, and have higher sensitivity, and ultimately improve the electrical performance of the sensor.

[0089] In some embodiments, the above-mentioned second buffer layer includes any one or more of an aluminum nitride buffer layer, a scandium-doped aluminum nitride buffer layer, a lead zirconate titanate buffer layer, a sodium potassium niobate buffer layer, and a lead magnesium niobate buffer layer;

[0090] The above-mentioned first buffer layer includes a magnesium oxide buffer layer;

[0091] The above-mentioned first buffer layer is disposed in contact with the above-mentioned first insulating layer, and the above-mentioned second buffer layer is disposed in contact with the above-mentioned first protective layer.

[0092] The second buffer layer of the present application mainly functions as a piezoelectric layer, which is beneficial to further converting the pressure signal into an electrical signal, enabling the second buffer layer to achieve high sensitivity and fast response capabilities in the MEMS pressure sensor.

[0093] In some embodiments of the present application, the aluminum nitride buffer layer of the present application has a certain piezoelectric coefficient, and the piezoelectric coefficient of the scandium-doped aluminum nitride buffer layer of the present application is higher than that of the aluminum nitride buffer layer.

[0094] The first buffer layer of the present application mainly functions as a heat conduction layer. On the one hand, the magnesium oxide buffer layer has high thermal stability itself. On the other hand, its heat conduction performance is also good, such as better than that of aluminum oxide. Therefore, it is beneficial to improve the temperature stability of the sensor as the second buffer layer, and further improve the electrical performance of the sensor.

[0095] In some embodiments of the present application, the first buffer layer and the second buffer layer have a certain thermal stability. For example, their thermal expansion coefficients are similar to those of the silicon oxide insulating layer and the silicon nitride protective layer, which can reduce thermal stress and thus improve the stability of the sensor under temperature changes.

[0096] In some embodiments, the ratio of the thickness of the above-mentioned first buffer layer to the thickness of the above-mentioned second buffer layer is (0.5 - 1):1.

[0097] The thickness of this application is consistent with the conventional definition in the art. This application mainly refers to the vertical depth or distance of each film layer, which can be measured by any conventional instrument in the art, such as an atomic force microscope.

[0098] In some embodiments of this application, the ratio of the thickness of the first buffer layer to the thickness of the second buffer layer is selected to be (0.5 - 1):1 to facilitate the second buffer layer and the first buffer layer to jointly achieve the technical purpose of improving the electrical performance of the sensor.

[0099] In some embodiments of this application, the ratio of the thickness of the first buffer layer to the thickness of the second buffer layer is any one of 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1 or any one within the range of any two of the above.

[0100] In some embodiments, the thickness of the above buffer layer is 1000 angstroms to 3000 angstroms.

[0101] The definition, measurement method, etc. of the thickness here in this application are the same as those above. The thickness of the buffer layer in this application includes the sum of the thickness of the second buffer layer and the thickness of the first buffer layer.

[0102] In some embodiments of this application, the thickness of the above buffer layer is any one of 1000 angstroms, 1100 angstroms, 1200 angstroms, 1300 angstroms, 1400 angstroms, 1500 angstroms, 1600 angstroms, 1700 angstroms, 1800 angstroms, 1900 angstroms, 2000 angstroms, 2100 angstroms, 2200 angstroms, 2300 angstroms, 2400 angstroms, 2500 angstroms, 2600 angstroms, 2700 angstroms, 2800 angstroms, 2900 angstroms, 3000 angstroms or any one within the range of any two of the above.

[0103] In some embodiments of this application, the thickness of the above first buffer layer is 1000 angstroms to 1500 angstroms.

[0104] In some embodiments of this application, the thickness of the above second buffer layer is 1000 angstroms to 2000 angstroms.

[0105] In some embodiments, the orthographic projection of the above cavity on the above silicon wafer cup-shaped structure layer completely overlaps with part of the above ion implantation block doping layer.

[0106] The orthographic projection of this application refers to a figure formed by a projection method in which the parallel projection lines of the projection figure are perpendicular to the above projection plane based on the projection plane (silicon wafer cup-shaped structure layer).

[0107] The ion implantation block doping layer of the present application itself has certain electrical properties. The present application selects to completely overlap the positive projection of the above cavity on the above silicon wafer cup-shaped structure layer with part of the above ion implantation block doping layer, which is beneficial to further and more effectively convert the pressure change into an electrical signal, and further improve the sensitivity and response characteristics of the sensor.

[0108] In some embodiments, the above cavity includes an open end facing the above substrate and a bottom end opposite to the open end. The distance between the open end and the bottom end is h1, and h1 is 350 μm to 390 μm; the thickness of the above silicon wafer cup-shaped structure layer is H, and H is 360 μm to 400 μm.

[0109] The present application selects h1 and H to satisfy the above numerical range, which is beneficial to better withstand and sense the pressure change.

[0110] In these embodiments of the present application, the distance h1 between the open end and the bottom end of the cavity is any one of 350 μm, 360 μm, 370 μm, 380 μm, 390 μm or any one that satisfies any two of the above range values.

[0111] In these embodiments of the present application, the thickness H of the silicon wafer cup-shaped structure layer is any one of 360 μm, 370 μm, 380 μm, 390 μm, 400 μm or any one that satisfies any two of the above range values.

[0112] In some embodiments, the stress cavity is any one or more of a cylindrical cavity, an elliptical cylindrical cavity, and a square cavity.

[0113] In some embodiments, the stress cavity is a cylindrical cavity, and the bottom diameter of the cylindrical cavity is 750 μm to 850 μm; the height of the cylindrical cavity is 360 μm to 400 μm.

[0114] In some embodiments, the size of the stress cavity is not particularly limited, and those skilled in the art can make a reasonable selection according to actual needs. As some specific examples, the size of the stress cavity can also be 750 μm × 360 μm, 750 μm × 400 μm, 800 μm × 360 μm, 800 μm × 400 μm, 850 μm × 360 μm, 850 μm × 400 μm, etc.

[0115] In some embodiments, the material of the metal layer includes but is not limited to aluminum.

[0116] In some embodiments, a phosphorus-doped polysilicon layer is provided between the first protective layer and the second insulating layer. The phosphorus-doped polysilicon layer covers part of the surface of the first protective layer and part of the surface of the phosphorus-doped polysilicon layer is exposed.

[0117] The phosphorus-doped polysilicon layer of the present application is beneficial to further improve the sensitivity and stability of the device in a high-temperature environment.

[0118] While the metal layer in the present application covers the first protective layer and fills the first through hole, the second through hole, and the third through hole, the metal layer is also in contact connection with the phosphorus-doped polysilicon layer.

[0119] In some embodiments, the substrate can be double-sided polished glass.

[0120] The second aspect of the present application is to provide a preparation method of the MEMS pressure sensor described in the first aspect. The preparation method is as Figure 1 shown, including the following preparation processes:

[0121] S100. Provide a silicon wafer;

[0122] S200. Form an ion implantation block doping layer on one side surface layer of the above silicon wafer;

[0123] S300. Grow a first insulating layer, a first buffer layer, a second buffer layer, and a first protective layer on one side of the above ion implantation block doping layer;

[0124] S400. Etch the above first insulating layer, buffer layer, and first protective layer to obtain a first through hole, a second through hole, and a third through hole that are connected;

[0125] S500. Grow a metal layer on the above first protective layer and fill the above third through hole, second through hole, and first through hole;

[0126] S600. Partially etch the above metal layer, grow a second insulating layer and a second protective layer on the etched metal layer, and etch the above second insulating layer and second protective layer to expose a part of the upper surface of the above metal layer;

[0127] S700. Etch a groove in the central area on the side of the above silicon wafer away from the above ion implantation block doping layer;

[0128] S800. Bond the silicon wafer with the groove and the substrate through a bonding process to form a cavity.

[0129] In some embodiments, the growth of the above first buffer layer is atomic layer deposition, and the deposition step includes:

[0130] Heat the surface to be deposited with the first buffer layer to 150°C to 350°C;

[0131] Introduce a magnesium precursor to the surface to be deposited with the first buffer layer, and control the pulse time to be 0.1 s to 2.0 s;

[0132] Introduce an oxidant to the surface to be deposited with the first buffer layer, and control the pulse time to be 0.1 s to 2.0 s;

[0133] The above deposition process is taken as one cycle and repeated multiple times in a loop.

[0134] In some embodiments, the surface of the first buffer layer to be deposited is heated to any one of 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C or any one within the range of any two of the above.

[0135] The pulse time in this application refers to the time when each precursor is introduced to the surface to be deposited during the ALD reaction process.

[0136] In some embodiments, a magnesium precursor is introduced to the surface of the first buffer layer to be deposited, and the pulse time is controlled to be any one of 0.1 s, 0.2 s, 0.3 s, 0.4 s, 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1 s, 1.1 s, 1.2 s, 1.3 s, 1.4 s, 1.5 s, 1.6 s, 1.7 s, 1.8 s, 1.9 s, 2.0 s or any one within the range of any two of the above.

[0137] In some embodiments, an oxidant is introduced to the surface of the first buffer layer to be deposited, and the pulse time is controlled to be any one of 0.1 s, 0.2 s, 0.3 s, 0.4 s, 0.5 s, 0.6 s, 0.7 s, 0.8 s, 0.9 s, 1 s, 1.1 s, 1.2 s, 1.3 s, 1.4 s, 1.5 s, 1.6 s, 1.7 s, 1.8 s, 1.9 s, 2.0 s or any one within the range of any two of the above.

[0138] In some embodiments, the above deposition process is cycled 2 to 20 times.

[0139] Atomic layer deposition (ALD) in this application is a high-precision thin film deposition technology based on chemical vapor deposition (CVD), which deposits material substances layer by layer on the substrate surface in the form of a single atomic layer. In this application, atomic layer deposition is used to form the first buffer layer. Among them, the thickness of MgO can be conveniently and precisely regulated through the number of ALD cycles to meet the miniaturization requirements of MEMS devices. At the same time, it can also avoid introducing additional parasitic capacitance. The ultra-thin and dense MgO buffer layer formed in this application achieves high conformal coverage, fully covers the three-dimensional structure in the MEMS sensor, ensures the uniformity of the buffer layer on complex morphologies, and improves the device yield.

[0140] In some embodiments, the above-mentioned magnesium precursor is a cyclopentadienyl compound of magnesium; the chemical formula of the cyclopentadienyl compound is C 10 H 10 Mg.

[0141] In some embodiments, the above-mentioned oxidant is ozone.

[0142] In some embodiments, the growth of the above-mentioned second buffer layer is plasma-enhanced chemical vapor deposition, and the deposition step includes:

[0143] Introduce a nitrogen precursor and an aluminum precursor to the surface of the second buffer layer to be deposited. The flow rate of the nitrogen precursor is 30 sccm to 70 sccm, the flow rate of the aluminum precursor is 3 sccm to 10 sccm, and the pressure is 80 Pa to 150 Pa;

[0144] Control the radio frequency power to be 250 W to 350 W, the deposition temperature to be 240 °C to 360 °C, and the deposition time to be 2 min to 3 min.

[0145] In this application, sccm is an abbreviation for Standard Cubic Centimeters per Minute, which means standard cubic centimeters per minute and is a unit used to describe gas flow rate.

[0146] The radio frequency power in this application refers to the measure of the energy transmitted per unit time in radio frequency (RF) signal transmission.

[0147] In some embodiments, introduce a nitrogen precursor to the surface of the second buffer layer to be deposited. The flow rate of the nitrogen precursor is any one of 30 sccm, 35 sccm, 40 sccm, 45 sccm, 50 sccm, 55 sccm, 60 sccm, 65 sccm, 70 sccm or any one that satisfies any two of the above range values.

[0148] In some embodiments, introduce an aluminum precursor to the surface of the second buffer layer to be deposited. The flow rate of the aluminum precursor is any one of 3 sccm, 3.5 sccm, 4 sccm, 4.5 sccm, 5 sccm, 5.5 sccm, 6 sccm, 6.5 sccm, 7 sccm, 7.5 sccm, 8 sccm, 8.5 sccm, 9 sccm, 9.5 sccm, 10 sccm or any one that satisfies any two of the above range values.

[0149] In some embodiments, a nitrogen precursor and an aluminum precursor are introduced onto the surface of the second buffer layer to be deposited, and the pressure is controlled to be any one of 80 Pa, 85 Pa, 90 Pa, 95 Pa, 100 Pa, 110 Pa, 120 Pa, 130 Pa, 140 Pa, 150 Pa or any one within the range of any two of the above.

[0150] In some embodiments, a nitrogen precursor and an aluminum precursor are introduced onto the surface of the second buffer layer to be deposited, and the radio frequency power is controlled to be any one of 250 W, 260 W, 270 W, 280 W, 290 W, 300 W, 310 W, 320 W, 330 W, 340 W, 350 W or any one within the range of any two of the above.

[0151] In some embodiments, a nitrogen precursor and an aluminum precursor are introduced onto the surface of the second buffer layer to be deposited, and the deposition temperature is controlled to be any one of 240 °C, 250 °C, 260 °C, 270 °C, 280 °C, 290 °C, 300 °C, 310 °C, 320 °C, 330 °C, 340 °C, 350 °C, 360 °C or any one within the range of any two of the above.

[0152] In some embodiments, a nitrogen precursor and an aluminum precursor are introduced onto the surface of the second buffer layer to be deposited, and the deposition time is controlled to be any one of 2 min, 2.5 min, 3 min or any one within the range of any two of the above.

[0153] This application adopts plasma enhanced chemical vapor deposition. First, this method has low-temperature deposition compatibility, and it can deposit AlN at a relatively low temperature (200 - 400 °C), avoiding thermal damage to the piezoresistive doping region or metal interconnection already integrated in the MEMS structure. Moreover, it also has a high deposition rate and uniformity. For example, it has a higher deposition rate (~10 nm / min), which is suitable for mass production requirements.

[0154] In some embodiments, the above nitrogen precursor is hydrogen nitride, and the above aluminum precursor is trimethylaluminum.

[0155] In some embodiments, the above ion implantation block doping layer includes a high-concentration N-type doping region (abbreviated as N+), a high-concentration P-type doping region (abbreviated as P+), and a low-concentration P-type doping region (abbreviated as P-).

[0156] In some embodiments, the formation process of the high-concentration N-type doping region includes: implanting phosphorus into the surface layer of the silicon wafer, with a phosphorus dose of 5e15 cm -2 , an energy of 80 keV, an inclination angle of 7°, and an implantation junction depth of 30 μm - 50 μm.

[0157] In some embodiments, the process of forming a high-concentration P-type doped region includes: boron is ion-implanted into the surface layer of the silicon wafer, with a boron dose of 1e16 cm -2 , an energy of 60 keV, an inclination angle of 7°, and an implantation junction depth of 20 μm to 30 μm.

[0158] In some embodiments, the process of forming a low-concentration P-type doped region includes: boron is ion-implanted into the surface layer of the silicon wafer, with a boron dose of 3e14 cm -2 , an energy of 40 keV, an inclination angle of 7°, and an implantation junction depth of 10 μm to 20 μm.

[0159] To better explain the present application, the following will be described in detail with specific embodiments.

[0160] Embodiment 1

[0161] A Figure 2 schematic MEMS pressure sensor is provided. As Figure 2 schematically shown, in this embodiment, a MEMS pressure sensor 1000 is provided. The sensor includes a substrate 1001, a silicon wafer cup-shaped structure layer 1002, a first insulating layer 1003, a first buffer layer 1004a, a second buffer layer 1004b, a first protective layer 1005, a metal layer 1006, a second insulating layer 1008, and a second protective layer 1009.

[0162] Among them, the silicon wafer cup-shaped structure layer 1002 is disposed on one side surface of the substrate 1001; a cavity 1002a is formed on the side of the silicon wafer cup-shaped structure layer 1002 facing the substrate 1001; on the surface layer of the silicon wafer cup-shaped structure layer 1002 facing away from the substrate 1001, a first ion implantation block doped layer 1002b, a second ion implantation block doped layer 1002c, and a third ion implantation block doped layer 1002d are formed. Among them, the first ion implantation block doped layer 1002b is a high-concentration N-type doped region, the second ion implantation block doped layer 1002c is a high-concentration P-type doped region, and the third ion implantation block doped layer 1002d is a low-concentration P-type doped region. The first insulating layer 1003 covers the ion implantation block doped layer, and the first insulating layer 1003 is provided with a first through hole for exposing a part of the upper surface of the ion implantation block doped layer, such as exposing the upper surfaces of the first ion implantation block doped layer 1002b and the second ion implantation block doped layer 1002c.

[0163] The above-mentioned first buffer layer 1004a is disposed in contact with the above-mentioned first insulating layer 1003, and the above-mentioned second buffer layer 1004b is disposed in contact with the above-mentioned first protective layer 1005. And second through-holes communicating with the above-mentioned first through-hole are provided on the first buffer layer 1004a and the second buffer layer 1004b, and third through-holes communicating with the above-mentioned second through-hole are provided on the first protective layer 1005. The metal layer 1006 fills the first through-hole, the second through-hole, and the third through-hole. The second insulating layer 1008 is disposed on the surface of the first protective layer 1005 facing away from the substrate 1001, and a part of the upper surface of the metal layer 1006 is exposed. The second insulating layer 1008 is provided with a fourth through-hole for exposing a part of the upper surface of the metal layer 1006. The second protective layer 1009 is disposed on the surface of the second insulating layer 1008 facing away from the substrate 1001, and the second protective layer 1009 is provided with a fifth through-hole communicating with the fourth through-hole.

[0164] And in combination Figure 2 It is also known that a phosphorus-doped polysilicon layer 1007 is provided between the first protective layer 1005 and the second insulating layer 1008. The phosphorus-doped polysilicon layer 1007 covers a part of the surface of the first protective layer 1005 and a part of the surface of the phosphorus-doped polysilicon layer 1007 is exposed in the fourth through-hole. While the metal layer 1006 covers the first protective layer 1005 and fills the first through-hole, the second through-hole, and the third through-hole, the metal layer 1006 is also in contact with the phosphorus-doped polysilicon layer 1007.

[0165] This embodiment Figure 2 The preparation method of the schematic MEMS pressure sensor is as Figures 3A to 3I schematic.

[0166] As Figure 3A schematic, the preparation method of the MEMS pressure sensor includes providing a silicon wafer 1002', forming a first ion implantation block doping layer 1002b, a second ion implantation block doping layer 1002c, and a third ion implantation block doping layer 1002d on one side surface layer of the silicon wafer 1002'. And the formation process of the first ion implantation block doping layer 1002b includes: implanting phosphorus into the surface layer of the corresponding position of the silicon wafer, the phosphorus dose is 5e15 cm -2 , the energy is 80 keV, the tilt angle is 7°, and the implantation junction depth is about 35 μm to form a high-concentration N-type doping region; the formation process of the second ion implantation block doping layer 1002c includes: implanting boron into the surface layer of the corresponding position of the silicon wafer, the boron dose is 1e16 cm -2 , the energy is 60 keV, the tilt angle is 7°, and the implantation junction depth is about 20 μm to form a high-concentration P-type doping region; the formation process of the third ion implantation block doping layer 1002d includes: implanting boron into the surface layer of the corresponding position of the silicon wafer, the boron dose is 3e14 cm -2, with an energy of 40 keV, an inclination angle of 7°, and an implantation junction depth of 11 μm to form a low-concentration P-type doping region.

[0167] As Figure 3B shown schematically, a first insulating layer 1003, a first buffer layer 1004a, a second buffer layer 1004b, and a first protective layer 1005 are sequentially grown on one side of the doped layer in the above ion implantation block;

[0168] Among them, the growth process of the first insulating layer 1003 (silicon oxide) includes: after the above ion implantation is completed, O2 is introduced, the temperature is adjusted to 1050 °C, and the growth thickness is 1200 angstroms.

[0169] The growth process of the first buffer layer 1004a (magnesium oxide) includes: adopting atomic layer deposition, heating the surface to be deposited with the first buffer layer to about 200 °C, introducing a magnesium precursor cyclopentadienyl compound to the surface to be deposited with the first buffer layer, and controlling the pulse time to 0.5 s; introducing an oxidant ozone to the surface to be deposited with the first buffer layer, and controlling the pulse time to 1.0 s; taking the above deposition process as one cycle, repeating the cycle 3 times, and the thickness of the formed first buffer layer 1004a (magnesium oxide) is 1000 angstroms.

[0170] The growth process of the second buffer layer 1004b (aluminum nitride) includes: adopting plasma-enhanced chemical vapor deposition, introducing a nitrogen precursor hydrogen nitride and an aluminum precursor trimethylaluminum to the surface to be deposited with the second buffer layer, the flow rate of hydrogen nitride is 65 sccm, the flow rate of trimethylaluminum is 8 sccm, and the pressure is controlled to 130 Pa; controlling the radio frequency power to 350 W, the deposition temperature to 360 °C, and the deposition time to 3.0 min, and the thickness of the formed second buffer layer 1004b is 2000 angstroms.

[0171] Among them, the thickness ratio of the first buffer layer 1004a (magnesium oxide) to the second buffer layer 1004b (aluminum nitride) is 0.5:1;

[0172] The growth process of the first protective layer 1005 (silicon nitride) includes: introducing SIH2Cl2 and NH3 to the surface to be deposited with the first protective layer, adjusting the temperature to about 650 °C, growing a silicon nitride protective layer with a thickness of 1200 angstroms as the first protective layer 1005, and the first protective layer 1005 is also a stress control layer, and the stress control layer is used to control the stress concentration degree between layers, thereby reducing the risk of film layer rupture or damage caused by stress concentration and ensuring long-term stable device operation.

[0173] As Figure 3CAs shown, a phosphorus-doped polysilicon layer 1007 is grown on the first protective layer 1005. After the growth of the phosphorus-doped polysilicon layer 1007 is completed, photolithographic patterning is performed on the phosphorus-doped polysilicon layer 1007. The minimum CD (feature size) after etching the phosphorus-doped polysilicon layer 1007 is 50 ± 5 μm.

[0174] As Figure 3D As shown, along the positive projections of the first ion implantation block doping layer 1002b and the second ion implantation block doping layer 1002c on the silicon wafer 1002', the first insulating layer 1003, the first buffer layer 1004a, the second buffer layer 1004b, and the first protective layer 1005 are etched along the thickness directions of the respective film layers, and the minimum CD after etching is 10 ± 2 μm. Correspondingly, a first through hole on the first insulating layer 1003, a second through hole on the first buffer layer 1004a and the second buffer layer 1004b, and a third through hole on the first protective layer are obtained, and the first through hole, the second through hole, and the third through hole are kept internally connected. These through holes facilitate the subsequent provision of metal electrical connection channels.

[0175] As Figure 3E As shown, a metal layer 1006 (aluminum) is regrown inside the above-mentioned first through hole, second through hole, and third through hole until it covers the first protective layer 1005. Specifically, a magnetron sputtering technology deposition method is used, the sputtering power is controlled at 300 W, and the deposition rate is The gas pressure is 3.5 mTorr, and the sputtering thickness is 13500 angstroms to fill the channels of each through hole. Then, Cl2 is used to etch the metal layer 1006 on the surface of the first protective layer 1005. The minimum CD after etching is 30 ± 2 μm, and the formed aluminum conductive layer pattern is as Figure 3F shown.

[0176] As Figure 3G As shown, on Figure 3F As shown, a second insulating layer 1008 and a second protective layer 1009 are grown on the metal layer 1006. Specifically, the growth process of the second insulating layer 1008 includes adjusting the furnace tube temperature to 300 °C, introducing O2, growing a 1300-angstrom-thick silicon oxide as the second insulating layer, then growing a silicon nitride layer with a thickness of 1500 angstroms as the second protective layer 1009, and then using Cl2 and CF4 to perform dry etching on the second protective layer 1009 and the second insulating layer 1008 respectively. After etching, the metal layer 1006 is opened to expose the upper surface of part of the metal layer 1006, and the minimum CD is 80 ± 5 μm.

[0177] As Figure 3HAs shown, a groove is etched on the side of the silicon wafer 1002' away from the doped layer of the above-mentioned ion implantation block. The groove is used to form a cavity 1002a. The process of etching the groove includes wet etching with KOH. Among them, the cavity 1002a includes an open end facing the above-mentioned substrate 1001 and a bottom end opposite to the open end. The distance between the open end and the bottom end is h1 (360 μm), and the thickness of the cup-shaped structure layer of the silicon wafer is H (380 μm).

[0178] As Figure 3I shown, the Figure 3H silicon wafer 1002' with a groove as shown is anodically bonded to the glass substrate 1001 to obtain Figure 2 the MEMS pressure sensor 1000 as shown.

[0179] Example 2

[0180] A method for preparing a Figure 2 MEMS pressure sensor as shown is provided. The difference between this preparation method and Example 1 is that:

[0181] The growth process of the first buffer layer 1004a (magnesium oxide) includes: adopting atomic layer deposition, heating the surface of the first buffer layer to be deposited to about 200 °C, introducing a magnesium precursor, cyclopentadienyl compound, to the surface of the first buffer layer to be deposited, and controlling the pulse time to be 0.5 s; introducing an oxidant, ozone, to the surface of the first buffer layer to be deposited, and controlling the pulse time to be 1.0 s; taking the above deposition process as one cycle, repeating it 3 times in a cycle, and the thickness of the formed first buffer layer 1004a (magnesium oxide) is 1000 angstroms.

[0182] The growth process of the second buffer layer 1004b (aluminum nitride) includes: adopting plasma-enhanced chemical vapor deposition, introducing a nitrogen precursor, hydrogen nitride, and an aluminum precursor, trimethylaluminum, to the surface of the second buffer layer to be deposited. The flow rate of hydrogen nitride is 50 sccm, the flow rate of trimethylaluminum is 5 sccm, and the pressure is controlled to be 100 Pa; controlling the radio frequency power to be 300 W, the deposition temperature to be 300 °C, and the deposition time to be 2.5 min, and the thickness of the formed second buffer layer 1004b is 1400 angstroms.

[0183] Among them, the ratio of the thickness of the first buffer layer 1004a (magnesium oxide) to the thickness of the second buffer layer 1004b (aluminum nitride) is 0.7:1.

[0184] Other aspects are the same as those in Example 1.

[0185] Example 3

[0186] A Figure 2Preparation method of a schematic MEMS pressure sensor, the difference between this preparation method and Example 1 lies in:

[0187] The growth process of the first buffer layer 1004a (magnesium oxide) includes: adopting atomic layer deposition, heating the surface to be deposited with the first buffer layer to about 200 °C, introducing a magnesium precursor cyclopentadienyl compound onto the surface to be deposited with the first buffer layer, and controlling the pulse time to be 0.5 s; introducing an oxidant ozone onto the surface to be deposited with the first buffer layer, and controlling the pulse time to be 1.0 s; taking the above deposition process as 1 cycle, repeating it 3 times cyclically, and the thickness of the formed first buffer layer 1004a (magnesium oxide) is 1000 angstroms.

[0188] The growth process of the second buffer layer 1004b (aluminum nitride) includes: adopting plasma-enhanced chemical vapor deposition, introducing a nitrogen precursor hydrogen nitride and an aluminum precursor trimethylaluminum onto the surface to be deposited with the second buffer layer, the flow rate of hydrogen nitride is 30 sccm, the flow rate of trimethylaluminum is 3 sccm, and controlling the pressure to be 80 Pa; controlling the radio frequency power to be 250 W, the deposition temperature to be 240 °C, and the deposition time to be 2.0 min, and the thickness of the formed second buffer layer 1004b is 1000 angstroms.

[0189] Among them, the thickness ratio of the first buffer layer 1004a (magnesium oxide) to the second buffer layer 1004b (aluminum nitride) is 1:1.

[0190] Other aspects are the same as those in Example 1.

[0191] Comparative Example 1

[0192] A preparation method of a MEMS pressure sensor is provided, the difference between this preparation method and Example 1 lies in:

[0193] Replace the first buffer layer 1004a (magnesium oxide) and the second buffer layer 1004b (aluminum nitride) with a single alumina layer, and the formation process of this alumina layer includes: adopting a magnetron sputtering process, introducing O2, the sputtering power of the Al target is 300 W, the gas pressure range is 5 mTorr, the deposition temperature is 150 °C, sputtering to form an alumina layer, and the thickness of this alumina layer is 2000 angstroms, and other aspects are the same as those in Example 1.

[0194] Test Example

[0195] I. Conduct a cyclic experiment at -40 °C → 150 °C to explore the thermal stability of the sensors in the above-mentioned examples and comparative examples.

[0196] (1) Experimental conditions:

[0197] Temperature range: -40 °C → 150 °C.

[0198] Number of cycles: 1000 times (according to MIL-STD-883 or JEDEC standards).

[0199] Cycling rate: Heating / cooling rate ≤ 10 °C / min (to avoid thermal shock).

[0200] Dwell time: Hold for 30 minutes each at high and low temperature stages.

[0201] Test samples:

[0202] Control group: Comparative examples.

[0203] Experimental group: Examples.

[0204] (2) Test parameters:

[0205] Zero Shift: The output offset of the sensor when there is no load.

[0206] Sensitivity Drift: The change rate of the full-scale output signal.

[0207] Specific test results are shown in Table 1:

[0208] Table 1

[0209]

[0210] Combined with Table 1, it can be seen that the design method provided by this application significantly improves the stability of the MEMS pressure sensor under cycling in a certain temperature range.

[0211] II. Explore the electrical properties of the sensors in the above examples and comparative examples:

[0212] Test the leakage current density of the examples and comparative examples. The specific test method can refer to the conventional design methods in the art. The specific results are shown in Table 2:

[0213] Table 2

[0214]

[0215] Combined with Table 2, it can be seen that the design method provided by this application can reduce the leakage current and optimize the electrical properties of the MEMS pressure sensor.

[0216] In summary, the design method provided by this application is conducive to obtaining a MEMS pressure sensor with good thermal stability and excellent electrical properties, which is beneficial to improving the performance and reliability of the entire sensor.

Claims

1. A MEMS pressure sensor, characterized in that: Comprising: A substrate; A silicon wafer cup-shaped structure layer: disposed on one side surface of the substrate; A cavity is formed on the side of the silicon wafer cup-shaped structure layer facing the substrate; An ion implantation block doping layer is formed on the surface layer of the silicon wafer cup-shaped structure layer on the side facing away from the substrate; A first insulating layer: covering the ion implantation block doping layer, and the first insulating layer is provided with a first through hole for exposing a part of the upper surface of the ion implantation block doping layer; A buffer layer: disposed on the side surface of the first insulating layer facing away from the substrate, and the buffer layer includes a first buffer layer and a second buffer layer which are stacked and have different materials, and a second through hole communicating with the first through hole is provided on the buffer layer; A first protective layer: disposed on the side surface of the buffer layer facing away from the substrate, and the first protective layer is provided with a third through hole communicating with the second through hole; A metal layer: filling the first through hole, the second through hole and the third through hole; A second insulating layer: disposed on the side surface of the first protective layer facing away from the substrate, and exposing a part of the upper surface of the metal layer; A second protective layer: disposed on the side surface of the second insulating layer facing away from the substrate.

2. The MEMS pressure sensor according to claim 1, wherein: The first buffer layer includes a magnesium oxide buffer layer; The second buffer layer includes any one or more of an aluminum nitride buffer layer, a scandium-doped aluminum nitride buffer layer, a lead zirconate titanate buffer layer, a sodium potassium niobate buffer layer, and a lead magnesium niobate buffer layer; The first buffer layer is disposed in a fitting manner with the first insulating layer, and the second buffer layer is disposed in a fitting manner with the first protective layer.

3. The MEMS pressure sensor according to any one of claims 1 to 2, characterized in that: The ratio of the thickness of the first buffer layer to the thickness of the second buffer layer is (0.5 - 1):

1.

4. The MEMS pressure sensor according to any one of claims 1 to 2, characterized in that: The thickness of the buffer layer is 1000 angstroms to 3000 angstroms.

5. The MEMS pressure sensor according to any one of claims 1 to 2, wherein: The orthographic projection of the cavity on the silicon wafer cup-shaped structure layer completely overlaps with a part of the ion implantation block doping layer; And / or; The cavity includes an open end facing the substrate and a bottom end opposite to the open end, and the distance between the open end and the bottom end is h1, and h1 is 350 μm to 390 μm; The thickness of the silicon wafer cup-shaped structure layer is H, and H is 360 μm to 400 μm.

6. A method for manufacturing the MEMS pressure sensor according to claim 1, characterized in that, Including the following preparation process: Providing a silicon wafer; Forming an ion implantation block doping layer on one side surface layer of the silicon wafer; Growing a first insulating layer, a first buffer layer, a second buffer layer and a first protective layer in sequence on one side of the ion implantation block doping layer; Etching the first insulating layer, the buffer layer and the first protective layer to obtain a first through hole, a second through hole and a third through hole that are communicated; Growing a metal layer on the first protective layer and filling the third through hole, the second through hole and the first through hole; Partially etching the metal layer, growing a second insulating layer and a second protective layer on the etched metal layer, and etching the second insulating layer and the second protective layer to expose a part of the upper surface of the metal layer; Etching a groove in the central region of the silicon wafer on the side facing away from the ion implantation block doping layer; Bonding the silicon wafer with the groove and the substrate through a bonding process to form a cavity.

7. The preparation method according to claim 6, characterized in that, The growth of the first buffer layer is by atomic layer deposition, and the deposition steps include: heating the surface to be deposited with the first buffer layer to 150°C to 350°C; introducing a magnesium precursor onto the surface to be deposited with the first buffer layer, and controlling the pulse time to be 0.1 s to 2.0 s; introducing an oxidant onto the surface to be deposited with the first buffer layer, and controlling the pulse time to be 0.1 s to 2.0 s; taking the above deposition process as one cycle, and repeating it multiple times in a cycle.

8. The preparation method according to claim 7, characterized in that, The magnesium precursor is a cyclopentadienyl compound of magnesium; The oxidant is ozone.

9. The preparation method according to any one of claims 6 to 8, characterized in that, The growth of the second buffer layer is by plasma enhanced chemical vapor deposition, and the deposition steps include: introducing a nitrogen precursor and an aluminum precursor onto the surface to be deposited with the second buffer layer, the flow rate of the nitrogen precursor being 30 sccm to 70 sccm, the flow rate of the aluminum precursor being 3 sccm to 10 sccm, and the pressure being 80 Pa to 150 Pa; controlling the radio frequency power to be 250 W to 350 W, the deposition temperature to be 240°C to 360°C, and the deposition time to be 2 min to 3 min.

10. The preparation method according to claim 9, characterized in that, The nitrogen precursor is hydrogen nitride, and the aluminum precursor is trimethylaluminum.

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