A high-sensitivity MEMS piezoresistive pressure sensor and its fabrication method

Abstract

This application relates to the field of semiconductor technology, specifically to a high-sensitivity MEMS piezoresistive pressure sensor and its fabrication method. The high-sensitivity MEMS piezoresistive pressure sensor includes: a sensitive thin film with a crystal plane of (100); a piezoresistor disposed in the tensile stress region of the sensitive thin film and arranged along the [010] or [001] crystal direction on the (100) crystal plane; a first structural layer disposed at the end of the piezoresistor near the center of the sensitive thin film; and a second structural layer disposed at the end of the piezoresistor away from the center of the sensitive thin film. When subjected to tensile stress, the first and second structural layers enable the upper and lower halves of the piezoresistor to exhibit a relative motion tendency parallel to the direction of the sensitive thin film along the thickness direction. This sensor can achieve pressure detection by relying on tangential stress, which is beneficial for improving the sensor's sensitivity.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and more specifically, to a high-sensitivity MEMS piezoresistive pressure sensor and its fabrication method. Background Technology

[0002] In recent years, with the rapid development of microelectronics and micro-electro-mechanical systems (MEMS) technologies, miniature sensors have been increasingly widely used in medical, industrial, aerospace, and consumer electronics fields. Pressure sensors are one of the important applications of MEMS technology, converting pressure signals into electrical signals to achieve accurate pressure measurement. Common MEMS piezoresistive pressure sensors typically employ a sensitive thin-film structure. Under external pressure, the sensitive thin film deforms, and the piezoresistive resistor located on the film undergoes a change in resistance based on the piezoresistive effect, thereby achieving pressure detection. The rate of change of the piezoresistive resistor conforms to the formula:

[0003] in, The longitudinal piezoresistive coefficient is... This is the lateral piezoresistive coefficient. The tangential piezoresistive coefficient is... , , They are respectively with , , The corresponding stress.

[0004] In the traditional MEMS piezoresistive pressure sensor manufacturing process, an N-type (100) crystal plane silicon substrate is typically used, and P-type ion implantation is performed along the

[110] crystal direction to form the piezoresistor. In this design, the piezoresistor is mainly subjected to normal stress ( and The effect of this is that the last term in the formula approximates zero. However, the tangential piezoresistive coefficient... It is usually much larger than the positive piezoresistive coefficient. and Therefore, the sensor primarily relies on normal stress, which limits its sensitivity. Furthermore, traditional MEMS piezoresistive pressure sensors experience zero-point temperature drift due to bonding thermal stress during the fabrication process, affecting the sensor's detection accuracy. This typically necessitates the use of low-temperature bonding processes, but this leads to weakened bonding strength and shortens the sensor's lifespan. Summary of the Invention

[0005] This application provides at least one high-sensitivity MEMS piezoresistive pressure sensor and its fabrication method. The sensor enables the pressure-sensitive film to effectively generate tangential stress during operation, and at the same time enhances the tangential piezoresistive effect of the piezoresistive resistor, so that the sensor can achieve pressure detection by relying on the tangential stress, thereby improving the sensitivity of the sensor.

[0006] In a first aspect, embodiments of this application provide a high-sensitivity MEMS piezoresistive pressure sensor, comprising: The sensitive thin film has a crystal plane of (100). A varistor is disposed in the tensile stress region of the sensitive film and arranged along the

[010] or

[001] crystal direction on the (100) crystal plane; The first structural layer is disposed in the tensile stress region of the sensitive film and located at one end of the piezoresistor near the center of the sensitive film; The second structural layer is disposed in the tensile stress region of the sensitive film and located at the end of the piezoresistor away from the center of the sensitive film; When subjected to tensile stress, the first and second structural layers can cause the upper and lower halves of the piezoresistor to exhibit a relative motion tendency parallel to the direction of the sensitive film along the thickness direction.

[0007] In one optional embodiment, the first structural layer and the second structural layer are located at opposite ends of the upper half of the varistor along the thickness direction, the elastic modulus of the first structural layer is greater than the elastic modulus of the varistor, and the elastic modulus of the second structural layer is less than the elastic modulus of the varistor.

[0008] In one alternative embodiment, the dimensions of both the first structural layer and the second structural layer along the stretching direction perpendicular to the varistor are larger than those of the varistor.

[0009] In one optional embodiment, the first structural layer and the second structural layer respectively wrap around both sides of the varistor along the direction perpendicular to the stretching direction, and the first structural layer and the second structural layer are connected at the centerline of the varistor.

[0010] In one alternative implementation, it further includes: A first insulating layer is located between the varistor and the first structural layer and the second structural layer.

[0011] Secondly, embodiments of this application also provide a method for fabricating a high-sensitivity MEMS piezoresistive pressure sensor, comprising: A monocrystalline silicon wafer with a crystal plane of (100) is provided, the monocrystalline silicon wafer having opposing first and second surfaces; A varistor is formed by P-type doping of the first surface along the

[010] or

[001] crystal orientation; A first groove is etched to form at one end of the varistor near the center of the first surface, and a first structural layer is formed in the first groove; A second groove is etched at one end of the varistor away from the center of the first surface, and a second structural layer is formed in the second groove; A cavity and a sensitive thin film are etched on the second surface, and the piezoresistor, the first structural layer and the second structural layer are all located in the tensile stress region of the sensitive thin film; When subjected to tensile stress, the first and second structural layers can cause the upper and lower halves of the piezoresistor to exhibit a relative motion tendency parallel to the direction of the sensitive film along the thickness direction.

[0012] In one optional embodiment, the first structural layer and the second structural layer are located at opposite ends of the upper half of the varistor along the thickness direction, the elastic modulus of the first structural layer is greater than the elastic modulus of the varistor, and the elastic modulus of the second structural layer is less than the elastic modulus of the varistor.

[0013] In one alternative embodiment, the dimensions of both the first structural layer and the second structural layer along the stretching direction perpendicular to the varistor are larger than those of the varistor.

[0014] In one optional embodiment, the first structural layer and the second structural layer respectively wrap around both sides of the varistor along the direction perpendicular to the stretching direction, and the first structural layer and the second structural layer are connected at the centerline of the varistor.

[0015] In an optional implementation, the method further includes: A first insulating layer is formed between the varistor and the first and second structural layers.

[0016] The above-mentioned technical solution of this application has the following beneficial technical effects: The high-sensitivity MEMS piezoresistive pressure sensor of this application embodiment, by setting a first structural layer and a second structural layer, enables the upper and lower halves of the piezoresistor to exhibit a relative motion tendency parallel to the sensitive film direction along the thickness direction when subjected to tensile stress. This allows the external pressure to be converted into tangential stress on the piezoresistor. Simultaneously, the piezoresistor is arranged along the

[010] or

[001] crystal orientation, enhancing the tangential piezoresistive effect. This allows the sensor to detect pressure by relying on tangential stress. Compared to traditional pressure sensors that primarily rely on the forward piezoresistive effect, the piezoresistive piezoresistive coefficient is larger, thus effectively improving the sensor's sensitivity.

[0017] Furthermore, since the piezoresistive resistors are arranged along the

[010] or

[001] crystal orientations, the forward piezoresistive coefficient is close to zero in these orientations. Therefore, when the sensor is subjected to thermal stress caused by temperature changes, the forward piezoresistive effect hardly occurs. This can significantly reduce the influence of temperature on the zero-point drift of the sensor, thereby eliminating the need for low-temperature bonding processes, maintaining high measurement accuracy of the sensor, and avoiding the lifespan issues caused by low-temperature bonding.

[0018] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. These drawings are incorporated in and constitute a part of this specification. They illustrate embodiments conforming to this application and, together with the specification, serve to explain the technical solutions of this application. It should be understood that the following drawings only show some embodiments of this application and should not be considered as limiting the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This paper shows a schematic diagram of the structure of a high-sensitivity MEMS piezoresistive pressure sensor provided in an embodiment of this application; Figures 2 to 17 The fabrication process of a high-sensitivity MEMS piezoresistive pressure sensor provided in the embodiments of this application is illustrated; In the figure: 1. Varistor; 2. Ohmic contact; 3. First structural layer; 4. Second structural layer; 5. First insulating layer; 6. Second insulating layer; 7. Electrode layer; 100. First substrate; 101. Sensitive thin film; 102. Cavity; 200. Second substrate. Detailed Implementation

[0021] Common MEMS piezoresistive pressure sensors typically employ a thin-film structure. Under external pressure, the thin film deforms, and the piezoresistive resistor located on the thin film changes resistance based on the piezoresistive effect, thus achieving pressure detection. The rate of change of the piezoresistive resistor conforms to the formula:

[0022] in, The longitudinal piezoresistive coefficient is... This is the lateral piezoresistive coefficient. The tangential piezoresistive coefficient is... , , They are respectively with , , The corresponding stress.

[0023] In the traditional MEMS piezoresistive pressure sensor manufacturing process, an N-type (100) crystal plane silicon substrate is typically used, and P-type ion implantation is performed along the

[110] crystal direction to form the piezoresistor. In this design, the piezoresistor is mainly subjected to normal stress ( and The effect of this is that the last term in the formula approximates zero. However, the tangential piezoresistive coefficient... It is usually much larger than the positive piezoresistive coefficient. and Therefore, the sensor primarily relies on normal stress, which limits its sensitivity. Furthermore, traditional MEMS piezoresistive pressure sensors experience zero-point temperature drift due to bonding thermal stress during the fabrication process, affecting the sensor's detection accuracy. This typically necessitates the use of low-temperature bonding processes, but this leads to weakened bonding strength and shortens the sensor's lifespan.

[0024] Therefore, this application provides a high-sensitivity MEMS piezoresistive pressure sensor. This sensor enables the pressure-sensitive film to effectively generate tangential stress during operation, and at the same time enhances the tangential piezoresistive effect of the piezoresistive resistor, so that the sensor can achieve pressure detection by relying on the tangential stress, thereby improving the sensitivity of the sensor.

[0025] The high-sensitivity MEMS piezoresistive pressure sensor provided in this application includes: The first substrate 100 has a sensitive thin film 101 with a crystal plane of (100); The second substrate 200 is bonded to the first substrate 100 to form a sealed cavity between the two; A varistor 1 is disposed in the tensile stress region of the sensitive film 101 and arranged along the

[010] or

[001] crystal orientation on the (100) crystal plane; The first structural layer 3 is disposed in the tensile stress region of the sensitive film 101 and located at one end of the piezoresistor 1 near the center of the sensitive film 101. The second structural layer 4 is disposed in the tensile stress region of the sensitive film 101 and located at the end of the piezoresistor 1 away from the center of the sensitive film 101. When subjected to tensile stress, the first structural layer 3 and the second structural layer 4 can cause the upper and lower halves of the varistor 1 to move relative to each other in the direction parallel to the sensitive film 101.

[0026] The high-sensitivity MEMS piezoresistive pressure sensor of this application embodiment, by setting a first structural layer 3 and a second structural layer 4, enables the upper and lower halves of the piezoresistive resistor 1 to exhibit a relative motion tendency parallel to the direction of the sensitive film 101 along the thickness direction when subjected to tensile stress. This allows the external pressure to be converted into tangential stress on the piezoresistive resistor 1. Simultaneously, the piezoresistive resistor 1 is arranged along the

[010] or

[001] crystal orientation, enhancing the tangential piezoresistive effect of the piezoresistive resistor 1. This allows the sensor to detect pressure by relying on tangential stress. Compared to traditional pressure sensors that mainly rely on the forward piezoresistive effect, the piezoresistive resistor 1 has a larger tangential piezoresistive coefficient, thereby effectively improving the sensor's sensitivity.

[0027] Furthermore, since the piezoresistive resistors 1 are arranged along the

[010] or

[001] crystal orientations, the forward piezoresistive coefficient is close to zero in these orientations. Therefore, when the sensor is subjected to thermal stress caused by temperature changes, the forward piezoresistive effect hardly occurs. This can significantly reduce the influence of temperature on the zero-point drift of the sensor, thereby eliminating the need for low-temperature bonding processes, maintaining high measurement accuracy of the sensor, and avoiding the lifespan issues caused by low-temperature bonding.

[0028] In some embodiments, the material of the varistor 1 can be P-type doped single-crystal silicon, the thickness can be 0.1-3μm, and the length and width can be determined specifically according to the design specifications.

[0029] In some embodiments, the varistor 1 has ohmic contacts 2 at both ends. The function of the ohmic contacts 2 is to provide a low-impedance current path, ensuring efficient signal transmission between the varistor 1 and the external circuit, and improving measurement accuracy. In specific implementations, the material of the ohmic contacts 2 can be P-type heavily doped single-crystal silicon, the thickness can be the same as that of the varistor 1, and the shape can be determined by the specific layout and wiring.

[0030] In some embodiments, the first structural layer 3 and the second structural layer 4 are located at opposite ends of the upper half of the varistor 1 along the thickness direction, respectively. The elastic modulus of the first structural layer 3 is greater than that of the varistor 1, and the elastic modulus of the second structural layer 4 is less than that of the varistor 1.

[0031] In the above scheme, when the sensor is subjected to external pressure, the pressure-sensitive film 101 bends downward. Simultaneously, compressive stress is generated in the central region of the film, while tensile stress is generated in the first structural layer 3, the second structural layer 4, and the varistor 1, located in the tensile stress region. Since the elastic modulus of the materials of the second structural layer 4, the varistor 1, and the first structural layer 3 increases sequentially, their strain decreases sequentially under tensile stress. This causes the first structural layer 3 and the second structural layer 4 to exhibit a relative motion tendency parallel to the direction of the sensitive film 101. Since the thickness of both the first structural layer 3 and the second structural layer 4 is half that of the varistor 1, this tendency also causes a relative motion tendency parallel to the direction of the sensitive film 101 between the upper and lower halves of the varistor 1 along its thickness direction, resulting in shear stress on the varistor 1. Therefore, according to the above scheme, the first structural layer 3 and the second structural layer 4 can convert the external pressure into the tangential stress on the piezoresistive resistor 1, and use the tangential piezoresistive effect to convert the pressure into the resistance change of the piezoresistive resistor 1, thereby realizing the detection of pressure.

[0032] In some embodiments, the material of the first structural layer 3 can be at least one of chromium, tungsten, nickel, iridium, and silicon nitride, which has a Young's modulus higher than that of single-crystal silicon, and its thickness is half that of the varistor 1. In specific embodiments, the first structural layer 3 can be formed by vapor deposition or sputtering. For example, the first structural layer 3 is formed by chemical vapor deposition.

[0033] In some embodiments, the material of the second structural layer 4 can be at least one of aluminum, titanium, gold, polycrystalline silicon, etc., with a Young's modulus lower than that of monocrystalline silicon, and its thickness is half that of the varistor 1. In specific embodiments, the second structural layer 4 can be formed by vapor deposition or sputtering. For example, the second structural layer 4 is formed by sputtering.

[0034] In some embodiments, the dimensions of the first structural layer 3 and the second structural layer 4 along the stretching direction perpendicular to the varistor 1 are both larger than the varistor 1. For example, along the stretching direction perpendicular to the varistor 1, the first structural layer 3 has a first dimension, the second structural layer 4 has a second dimension, and the varistor 1 has a third dimension, wherein the first dimension and the second dimension are equal, and both the first dimension and the second dimension are larger than the third dimension.

[0035] In the above scheme, by designing the first structural layer 3 and the second structural layer 4 to be larger, the externally applied pressure can be transmitted more evenly to the varistor 1 region, and a stress concentration effect can be formed near the varistor 1. This concentration effect causes the varistor 1 to experience greater strain, thereby improving the sensitivity of the sensor.

[0036] It should be noted that a piezoresistive resistor 1 can be set in the tensile stress area around the sensor, and a first structural layer 3 and a second structural layer 4 are respectively set at both ends of each piezoresistive resistor 1. In this case, since the first structural layer 3 and the second structural layer 4 have long dimensions, adjacent first structural layers 3 or second structural layers 4 can intersect or connect.

[0037] In some embodiments, the first structural layer 3 and the second structural layer 4 are respectively wrapped around the two sides of the varistor 1 along the direction perpendicular to the stretching direction, and the first structural layer 3 and the second structural layer 4 are connected at the centerline of the varistor 1.

[0038] In the above scheme, the first structural layer 3 and the second structural layer 4 respectively wrap around both sides of the varistor 1, which can more evenly transmit the externally applied pressure to the varistor 1 region. In this way, the problems of stress concentration or stress dispersion can be avoided. Furthermore, the design of the first structural layer 3 and the second structural layer 4 connecting at the centerline of the varistor 1 ensures the symmetry of the two structural layers. This symmetry helps to ensure the uniform distribution of the stress field, thereby improving measurement accuracy. In addition, this design can also restrict the degrees of freedom of the varistor 1, causing it to strain only in the expected direction, thereby improving measurement accuracy.

[0039] In some embodiments, the high-sensitivity MEMS piezoresistive pressure sensor further includes a first insulating layer 5, which is located between the piezoresistive resistor 1 and the first structural layer 3 and the second structural layer 4. Specifically, the first insulating layer 5 is disposed circumferentially around the piezoresistive resistor 1, and the thickness of the first insulating layer 5 is equal to the thickness of the first structural layer 3 and the second structural layer 4. In specific implementations, the material of the first insulating layer 5 can be at least one of silicon dioxide or silicon nitride, and the width can be 0.3-1 μm.

[0040] In the above scheme, by setting a first insulating layer 5 between the varistor 1 and the first structural layer 3 and the second structural layer 4, electrical isolation between the varistor 1 and the first structural layer 3 and the second structural layer 4 can be achieved. This prevents the formation of parasitic capacitance or inductance between the varistor 1 and the first structural layer 3 and the second structural layer 4, thereby avoiding parasitic effects interfering with the acquisition of electrical signals and improving measurement accuracy.

[0041] In some embodiments, the high-sensitivity MEMS piezoresistive pressure sensor further includes a second insulating layer 6, which covers the sensitive film 101, the piezoresistive resistor 1, the first insulating layer 5, the first structural layer 3, and the second structural layer 4. In specific embodiments, the material of the second insulating layer 6 can be at least one of silicon dioxide or silicon nitride, and the thickness can be 100-500 nm.

[0042] In the above scheme, by setting a second insulating layer 6 to cover the sensitive film 101 and the varistor 1, electrical isolation between the sensitive film 101 and the varistor 1 and the outside world can be achieved. This prevents the sensitive film 101 and the varistor 1 from coming into contact with external conductive materials, thus preventing short circuits. In addition, the second insulating layer 6 can also protect the sensitive film 101 and the varistor 1, extending the service life of the sensor.

[0043] In some embodiments, an electrode layer 7 for connecting the ohmic contact 2 is disposed on the top surface of the second insulating layer 6. In specific embodiments, the electrode layer 7 can be made of metal, preferably at least one of aluminum, copper, platinum, titanium, gold, etc., and its thickness can be 50-500 nm.

[0044] In the above scheme, by setting the electrode layer 7 to connect with the ohmic contact 2, the electrical signal generated by the varistor 1 can be transmitted to the external circuit to realize the acquisition and transmission of electrical signals.

[0045] This application also provides a method for fabricating a high-sensitivity MEMS piezoresistive pressure sensor, comprising: A single-crystal silicon wafer with a thickness of 300-500 μm and a crystal plane of (100) is provided as a first substrate 100, the single-crystal silicon wafer having a first surface and a second surface opposite to each other; A varistor 1 with a thickness of 0.1-3 μm is formed by P-type doping along the

[010] or

[001] crystal orientation on the first surface. The length and width of the varistor 1 can be determined according to the design specifications. P-type heavy doping is performed at both ends of the varistor 1 to form ohmic contacts 2. The thickness of the ohmic contacts 2 can be the same as that of the varistor 1, and the shape can be determined by the specific layout and wiring. A first groove is etched at one end of the varistor 1 near the center of the first surface, and a first structural layer 3 is formed in the first groove; A second groove is etched at one end of the varistor 1 away from the center of the first surface, and a second structural layer 4 is formed in the second groove; A cavity 102 and a sensitive thin film 101 are formed by etching on the second surface. The piezoresistor 1, the first structural layer 3 and the second structural layer 4 are all located in the tensile stress region of the sensitive thin film 101. A single-crystal silicon or glass with a thickness of 300-500μm is provided as a second substrate 200, and the second substrate 200 is bonded to a second surface to form a sealed cavity; When subjected to tensile stress, the first structural layer 3 and the second structural layer 4 can cause the upper and lower halves of the varistor 1 to move relative to each other in the direction parallel to the sensitive film 101.

[0046] The high-sensitivity MEMS piezoresistive pressure sensor prepared by the method in this application embodiment, by setting a first structural layer 3 and a second structural layer 4, enables the upper and lower halves of the piezoresistive resistor 1 to exhibit a relative motion tendency parallel to the direction of the sensitive film 101 when subjected to tensile stress. This allows the external pressure to be converted into tangential stress on the piezoresistive resistor 1. Simultaneously, the piezoresistive resistor 1 is arranged along the

[010] or

[001] crystal orientation, enhancing the tangential piezoresistive effect of the piezoresistive resistor 1. This allows the sensor to detect pressure by relying on tangential stress. Compared to traditional pressure sensors that mainly rely on the forward piezoresistive effect, the piezoresistive resistor 1 has a larger tangential piezoresistive coefficient, thereby effectively improving the sensor's sensitivity.

[0047] Furthermore, since the piezoresistive resistors 1 are arranged along the

[010] or

[001] crystal orientations, the forward piezoresistive coefficient is close to zero in these orientations. Therefore, when the sensor is subjected to thermal stress caused by temperature changes, the forward piezoresistive effect hardly occurs. This can significantly reduce the influence of temperature on the zero-point drift of the sensor, thereby eliminating the need for low-temperature bonding processes, maintaining high measurement accuracy of the sensor, and avoiding the lifespan issues caused by low-temperature bonding.

[0048] It should be noted that the method provided in this application embodiment is to first prepare a varistor 1, a first structural layer 3, and a second structural layer 4 on a single-crystal silicon wafer, and then prepare the single-crystal silicon wafer into a sensitive thin film 101. Of course, in other possible embodiments, the single-crystal silicon wafer can also be prepared into a sensitive thin film 101 first, and then the varistor 1, the first structural layer 3, and the second structural layer 4 can be prepared on the sensitive thin film 101.

[0049] In some embodiments, the first structural layer 3 and the second structural layer 4 are located at opposite ends of the upper half of the varistor 1 along the thickness direction, respectively. The elastic modulus of the first structural layer 3 is greater than that of the varistor 1, and the elastic modulus of the second structural layer 4 is less than that of the varistor 1.

[0050] In the above scheme, when the sensor is subjected to external pressure, the pressure-sensitive film 101 bends downward. Simultaneously, compressive stress is generated in the central region of the film, while tensile stress is generated in the first structural layer 3, the second structural layer 4, and the varistor 1, located in the tensile stress region. Since the elastic modulus of the materials of the second structural layer 4, the varistor 1, and the first structural layer 3 increases sequentially, their strain decreases sequentially under tensile stress. This causes the first structural layer 3 and the second structural layer 4 to exhibit a relative motion tendency parallel to the direction of the sensitive film 101. Since the thickness of both the first structural layer 3 and the second structural layer 4 is half that of the varistor 1, this tendency also causes a relative motion tendency parallel to the direction of the sensitive film 101 between the upper and lower halves of the varistor 1 along its thickness direction, resulting in shear stress on the varistor 1. Therefore, according to the above scheme, the first structural layer 3 and the second structural layer 4 can convert the external pressure into the tangential stress on the piezoresistive resistor 1, and use the tangential piezoresistive effect to convert the pressure into the resistance change of the piezoresistive resistor 1, thereby realizing the detection of pressure.

[0051] In some embodiments, the material of the first structural layer 3 can be at least one of chromium, tungsten, nickel, iridium, and silicon nitride, which has a Young's modulus higher than that of single-crystal silicon, and its thickness is half that of the varistor 1. In specific embodiments, the first structural layer 3 can be formed by vapor deposition or sputtering. For example, the first structural layer 3 is formed by chemical vapor deposition.

[0052] In some embodiments, the material of the second structural layer 4 can be at least one of aluminum, titanium, gold, polycrystalline silicon, etc., with a Young's modulus lower than that of monocrystalline silicon, and its thickness is half that of the varistor 1. In specific embodiments, the second structural layer 4 can be formed by vapor deposition or sputtering. For example, the second structural layer 4 is formed by sputtering.

[0053] In some embodiments, the dimensions of the first structural layer 3 and the second structural layer 4 along the stretching direction perpendicular to the varistor 1 are both larger than the varistor 1. For example, along the stretching direction perpendicular to the varistor 1, the first structural layer 3 has a first dimension, the second structural layer 4 has a second dimension, and the varistor 1 has a third dimension, wherein the first dimension and the second dimension are equal, and both the first dimension and the second dimension are larger than the third dimension.

[0054] In the above scheme, by designing the first structural layer 3 and the second structural layer 4 to be larger, the externally applied pressure can be transmitted more evenly to the varistor 1 region, and a stress concentration effect can be formed near the varistor 1. This concentration effect causes the varistor 1 to experience greater strain, thereby improving the sensitivity of the sensor.

[0055] It should be noted that a piezoresistive resistor 1 can be set in the tensile stress area around the sensor, and a first structural layer 3 and a second structural layer 4 are respectively set at both ends of each piezoresistive resistor 1. In this case, since the first structural layer 3 and the second structural layer 4 have long dimensions, adjacent first structural layers 3 or second structural layers 4 can intersect or connect.

[0056] In some embodiments, the first structural layer 3 and the second structural layer 4 are respectively wrapped around the two sides of the varistor 1 along the direction perpendicular to the stretching direction, and the first structural layer 3 and the second structural layer 4 are connected at the centerline of the varistor 1.

[0057] In the above scheme, the first structural layer 3 and the second structural layer 4 respectively wrap around both sides of the varistor 1, which can more evenly transmit the externally applied pressure to the varistor 1 region. In this way, the problems of stress concentration or stress dispersion can be avoided. Furthermore, the design of the first structural layer 3 and the second structural layer 4 connecting at the centerline of the varistor 1 ensures the symmetry of the two structural layers. This symmetry helps to ensure the uniform distribution of the stress field, thereby improving measurement accuracy. In addition, this design can also restrict the degrees of freedom of the varistor 1, causing it to strain only in the expected direction, thereby improving measurement accuracy.

[0058] In some embodiments, the method further includes forming a first insulating layer 5 between the varistor 1 and the first structural layer 3 and the second structural layer 4. In specific embodiments, the material of the first insulating layer 5 may be at least one of silicon dioxide or silicon nitride, and the width may be 0.3-1 μm.

[0059] In the above scheme, by setting a first insulating layer 5 between the varistor 1 and the first structural layer 3 and the second structural layer 4, electrical isolation between the varistor 1 and the first structural layer 3 and the second structural layer 4 can be achieved. This prevents the formation of parasitic capacitance or inductance between the varistor 1 and the first structural layer 3 and the second structural layer 4, thereby avoiding parasitic effects interfering with the acquisition of electrical signals and improving measurement accuracy.

[0060] In some embodiments, the method further includes forming a second insulating layer 6 on the first surface, the second insulating layer 6 covering the varistor 1, the first insulating layer 5, the first structural layer 3, and the second structural layer 4. In specific embodiments, the material of the second insulating layer 6 may be at least one of silicon dioxide or silicon nitride, and the thickness may be 100-500 nm.

[0061] In the above scheme, by setting a second insulating layer 6 to cover the sensitive film 101 and the varistor 1, electrical isolation between the sensitive film 101 and the varistor 1 and the outside world can be achieved. This prevents the sensitive film 101 and the varistor 1 from coming into contact with external conductive materials, thus preventing short circuits. In addition, the second insulating layer 6 can also protect the sensitive film 101 and the varistor 1, extending the service life of the sensor.

[0062] In some embodiments, the method further includes: etching a third groove in the second insulating layer 6, and forming an electrode layer 7 connected to the ohmic contact 2 in the third groove and on the surface of the second insulating layer 6. In specific embodiments, the electrode layer 7 can be made of metal, preferably at least one of aluminum, copper, platinum, titanium, gold, etc., and its thickness can be 50-500 nm.

[0063] In the above scheme, by setting the electrode layer 7 to connect with the ohmic contact 2, the electrical signal generated by the varistor 1 can be transmitted to the external circuit to realize the acquisition and transmission of electrical signals.

[0064] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "multiple" means two or more. Furthermore, "and / or" in the specification and claims indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0065] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0066] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0067] One or more embodiments in this specification are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this specification should be included within the protection scope of this application.

[0068] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A high-sensitivity MEMS piezoresistive pressure sensor, characterized in that, include: The sensitive thin film has a crystal plane of (100). A varistor is disposed in the tensile stress region of the sensitive film and arranged along the [010] or [001] crystal direction on the (100) crystal plane; The first structural layer is disposed in the tensile stress region of the sensitive film and located at one end of the piezoresistor near the center of the sensitive film; The second structural layer is disposed in the tensile stress region of the sensitive film and located at the end of the piezoresistor away from the center of the sensitive film; When subjected to tensile stress, the first and second structural layers can cause the upper and lower halves of the piezoresistor to exhibit a relative motion tendency parallel to the direction of the sensitive film along the thickness direction.

2. The high-sensitivity MEMS piezoresistive pressure sensor according to claim 1, characterized in that, The first structural layer and the second structural layer are located at opposite ends of the upper half of the varistor along the thickness direction. The elastic modulus of the first structural layer is greater than that of the varistor, and the elastic modulus of the second structural layer is less than that of the varistor.

3. The high sensitivity MEMS piezoresistive pressure sensor of claim 2, wherein, The dimensions of both the first structural layer and the second structural layer along the stretching direction perpendicular to the varistor are larger than those of the varistor.

4. The high sensitivity MEMS piezoresistive pressure sensor of claim 3, wherein, The first structural layer and the second structural layer respectively wrap around the two sides of the varistor perpendicular to the stretching direction, and the first structural layer and the second structural layer are connected at the center line of the varistor.

5. The high-sensitivity MEMS piezoresistive pressure sensor according to claim 1, characterized in that, Also includes: A first insulating layer is located between the varistor and the first structural layer and the second structural layer.

6. A method of fabricating a high sensitivity MEMS piezoresistive pressure sensor, characterized by, include: A monocrystalline silicon wafer with a crystal plane of (100) is provided, the monocrystalline silicon wafer having opposing first and second surfaces; A varistor is formed by P-type doping of the first surface along the [010] or [001] crystal orientation; A first groove is etched to form at one end of the varistor near the center of the first surface, and a first structural layer is formed in the first groove; A second groove is etched at one end of the varistor away from the center of the first surface, and a second structural layer is formed in the second groove; A cavity and a sensitive thin film are etched on the second surface, and the piezoresistor, the first structural layer and the second structural layer are all located in the tensile stress region of the sensitive thin film; When subjected to tensile stress, the first and second structural layers can cause the upper and lower halves of the piezoresistor to exhibit a relative motion tendency parallel to the direction of the sensitive film along the thickness direction.

7. The method of claim 6, wherein, The first structural layer and the second structural layer are located at opposite ends of the upper half of the varistor along the thickness direction. The elastic modulus of the first structural layer is greater than that of the varistor, and the elastic modulus of the second structural layer is less than that of the varistor.

8. The method of claim 7, wherein, The dimensions of both the first structural layer and the second structural layer along the stretching direction perpendicular to the varistor are larger than those of the varistor.

9. The method according to claim 8, characterized in that, The first structural layer and the second structural layer respectively wrap around the two sides of the varistor perpendicular to the stretching direction, and the first structural layer and the second structural layer are connected at the center line of the varistor.

10. The method according to claim 6, characterized in that, The method further includes: A first insulating layer is formed between the pressure-sensitive resistor and the first structural layer and the second structural layer. A first insulating layer is formed between the pressure-sensitive resistor and the first structural layer and the second structural layer.

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