Piezoresistive MEMS pressure sensor

Abstract

The utility model provides a piezoresistive MEMS pressure sensor which comprises an insulating layer, the upper surface of the insulating layer is provided with a pressure-sensitive film, and the lower surface of the insulating layer is provided with a pressure sensing sheet; wherein a lead and a piezoresistor are arranged on the surface of the pressure-sensitive film, and the lead is electrically connected with the piezoresistor; and the piezoresistor is a metal film. According to the piezoresistor, a resistance bridge structure with small thickness, small line width and high uniformity is realized through metal film etching, and the performance of the piezoresistive MEMS pressure sensor is improved.

Description

Technical Field

[0001] The present application relates to the technical field of integrated circuits, and in particular to a piezoresistive MEMS pressure sensor. Background Art

[0002] MEMS (Micro-Electro-Mechanical System) pressure sensors are micro devices with pressure detection capabilities made through MEMS technology. They are mainly divided into three categories: piezoresistive, capacitive, and resonant. They are used in consumer electronics, industrial production, and other fields. Among them, piezoresistive MEMS pressure sensors have the advantages of small size, light weight, simple structure, low cost, and high measurement accuracy, so they have been widely used.

[0003] However, when constructing a Wheatstone bridge, existing pressure sensors need to use ions or diffusion equipment to implant and form strain detection resistors, which is a complex process and has poor resistor size accuracy. Therefore, it is necessary to design a pressure sensor that realizes a resistor bridge structure with small thickness, small line width and high uniformity to improve the performance of piezoresistive MEMS pressure sensors. Utility Model Content

[0004] The present application provides a piezoresistive MEMS pressure sensor, which can realize a resistance bridge structure with small thickness, small line width and high uniformity, thereby improving the performance of the piezoresistive MEMS pressure sensor.

[0005] A piezoresistive MEMS pressure sensor provided according to an embodiment of the present specification includes an insulating layer, a pressure-sensitive film is provided on the upper surface of the insulating layer, and a pressure sensing sheet is provided on the lower surface; wherein a lead and a piezoresistor are provided on the surface of the pressure-sensitive film, and the lead and the piezoresistor are electrically connected; and the piezoresistor is a metal film.

[0006] Furthermore, the thickness range of the varistor is

[0007] Furthermore, the thickness of the varistor is

[0008] Furthermore, the line width of the varistor ranges from 0 to 15 um.

[0009] Furthermore, the line width of the varistor is 5 um.

[0010] Furthermore, the width difference of the horizontal cross section between the varistors is less than or equal to 0.02 um.

[0011] Furthermore, the material of the varistor is NiCr, Pt, FeNi, TiB, TaN or TiN; the insulating layer is SiO2 One or a combination of a layer, a SiN layer or a Glass layer; the material of the lead is Al, Ti / Al, Au or Cr / Au.

[0012] Furthermore, four varistors are provided, and the orthographic projections of the four varistors on the upper surface of the insulating layer are located on the same circle and are evenly distributed on the circle.

[0013] Furthermore, the varistor is in a bent shape.

[0014] Furthermore, the varistor includes multiple first resistance segments and multiple second resistance segments, two adjacent first resistance segments are connected through the second resistance segment, the length of the first resistance segment is greater than the second resistance segment, and the extension direction of the first resistance segment is different from the extension direction of the second resistance segment.

[0015] Furthermore, the first resistance segments of the four varistors extend in the same direction, and the second resistance segments of the four varistors extend in the same direction.

[0016] Furthermore, the piezoresistive MEMS pressure sensor also includes a substrate, the upper surface of which is provided with a second bonding seed metal layer and a second eutectic solder in sequence from bottom to top; and the lower surface of the corresponding pressure sensing sheet is provided with a first bonding seed metal layer and a first eutectic solder in sequence from top to bottom;

[0017] The first bonding seed metal layer and the second bonding seed metal layer are eutectic bonded together by the first eutectic solder and the second eutectic solder.

[0018] Furthermore, the pressure sensing sheet includes, from top to bottom, an SOI device layer, an SOI buried oxide layer and an SOI base layer, and a first cavity is formed on the lower surface of the SOI base layer by etching; a second cavity connected to the base is provided on the second bonding seed metal layer and the second eutectic solder, and a getter is provided on the upper surface of the base, and the getter is arranged in the second cavity;

[0019] Wherein, when the first eutectic solder and the second eutectic solder are eutectically bonded together, the position of the getter corresponds to the first cavity.

[0020] Furthermore, the first bonding seed metal layer and the second bonding seed metal layer are Cr / Au layers, Ti / Cr / Au layers or Cr / Ni / Au layers; the first eutectic solder and the second eutectic solder are AuSn, AgSn, CuSn or SnAgCu solder.

[0021] Further, the size of the first eutectic solder is smaller than or equal to the size of the first bonding seed metal layer; and the size of the second eutectic solder is smaller than or equal to the size of the second bonding seed metal layer.

[0022] Further, the first bonding seed metal layer and the second bonding seed metal layer have the same size;

[0023] Wherein, when the first eutectic solder and the second eutectic solder are eutectic bonded together, the first bonding seed metal layer corresponds to the second bonding seed metal layer in position.

[0024] Furthermore, there is a gap between the second outer edge of the first bonding seed metal layer and the first outer edge of the pressure sensing sheet, and there is a gap between the second inner edge of the first bonding seed metal layer and the first inner edge of the pressure sensing sheet.

[0025] Furthermore, there is a gap between the third outer edge of the second bonding seed metal layer and the fifth outer edge of the substrate; and there is a gap between the fourth outer edge of the second cavity and the third inner edge of the second bonding seed metal layer.

[0026] This application has the following beneficial effects:

[0027] This embodiment discloses a piezoresistive MEMS pressure sensor, wherein a piezoresistive film is provided on the upper surface of an insulating layer, and a pressure sensing sheet is provided on the lower surface; wherein a lead and a piezoresistor are provided on the surface of the piezoresistive film, and the lead and the piezoresistor are electrically connected; the piezoresistor is a metal film. The piezoresistor realizes a resistance bridge structure with a small thickness, a small line width and high uniformity through etching of the metal film, thereby improving the performance of the piezoresistive MEMS pressure sensor.

[0028] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the specification and, together with the description, serve to explain the principles of the specification.

[0030] Figure 1 is a schematic diagram of the structure of a piezoresistive MEMS pressure sensor in an embodiment of the present application;

[0031] Figure 2 is a side view of a piezoresistive MEMS pressure sensor in one embodiment of the present application;

[0032] Figure 3 is a schematic diagram of the structure of the varistor in an embodiment of the present application;

[0033] Figure 4 is a top view of the pressure sensing sheet in the embodiment of the present application;

[0034] Figure 5 is a bottom view of the pressure sensing sheet in the embodiment of the present application;

[0035] Figure 6 is a top view of a substrate in an embodiment of the present application;

[0036] Figure 7 is a side view of a piezoresistive MEMS pressure sensor in another embodiment of the present application.

[0037] Description of reference numerals:

[0038] 10-pressure sensor sheet; 11-SOI device layer; 12-SOI buried oxide layer; 13-SOI base layer; 131-first cavity; 14-first bonding seed metal layer; 141-second outer edge; 142-second inner edge; 15-first eutectic solder; 16-first outer edge; 17-first inner edge;

[0039] 20-substrate; 21-second bonding seed metal layer; 211-third outer edge; 212-third inner edge; 22-second eutectic solder; 23-getter; 24-fifth outer edge; 25-vent; 26-second cavity; 261-fourth outer edge;

[0040] 30-insulating layer; 311-first side; 312-second side; 313-third side; 314-fourth side; 32-varistor; 320-dashed box; 3201-first resistance segment; 3202-second resistance segment; 321-first varistor; 3211-first fold line point; 3212-second fold line point; 3213-third fold line point; 3214-fourth fold line point; 322-second varistor; 323-third varistor; 324-fourth varistor; 33-lead; 34-pad;

[0041] 40-Pressure sensitive film. DETAILED DESCRIPTION

[0042] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described in the following exemplary embodiments do not represent all implementations consistent with this specification. Instead, they are merely examples of devices and methods consistent with some aspects of this specification as detailed in the appended claims.

[0043] The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit this specification. The singular forms "a", "the" and "the" used in this specification and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0044] It should be understood that although the terms first, second, third, etc. may be used in this specification to describe various information, this information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of this specification, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining".

[0045] Next, the embodiments of this specification are described in detail.

[0046] Reference Figure 1 As shown, this embodiment discloses a piezoresistive MEMS pressure sensor, which includes an insulating layer 30, a pressure sensing sheet 10 is provided on the lower surface of the insulating layer 30, a pressure-sensitive film 40 is provided on the upper surface of the insulating layer 30, and a lead 33 and a piezoresistor 32 are provided on the surface of the piezoresistive film 40, and the piezoresistor 32 is electrically connected to the lead 33. The piezoresistor 32 is a metal film.

[0047] In this embodiment, the piezoresistive MEMS pressure sensor further includes a pad 34, which is disposed on the surface of the pressure-sensitive film 40, and the leads 33 are electrically connected via the pad 34. Of course, in another achievable manner, the pad 34 may also be disposed on the side of the pressure-sensitive film 40 or the pressure sensor sheet 10, and the specific position of the pad 34 is not limited here.

[0048] In one practicable manner, the varistor 32 is connected with the lead 33 and the pad 34 to form a Wheatstone bridge.

[0049] The leads 33 , the pads 34 and the varistor 32 on the upper surface of the insulating layer 30 can be formed by etching the corresponding metal films.

[0050] Compared with the existing pressure sensor, which needs to be implanted and formed into strain detection resistors through ions or diffusion equipment when constructing a Wheatstone bridge, the piezoresistive MEMS pressure sensor provided in this embodiment realizes a resistance bridge structure with small thickness, small line width and high uniformity, thereby improving the performance of the pressure sensor.

[0051] Specifically:

[0052] In one possible implementation, refer to Figure 1 and Figure 3 As shown, the pad 34 is connected to four varistors 32 through the lead 33 and transmits signals. Under the action of pressure, the varistor 32 is subjected to stress and the resistance value changes, and finally the resistance change is converted into a voltage output through the Wheatstone bridge, so the magnitude of the external pressure can be reflected by the voltage output value.

[0053] In one possible implementation, when pad 34 is Figure 1 and Figure 3 When there are four pads as shown, there is one ground terminal GND correspondingly; in another achievable manner, when there are five pads 34, there are two ground terminals GND correspondingly.

[0054] In the present embodiment, four varistors 32 are provided, and the orthographic projections of the four varistors 32 on the upper surface of the insulating layer 30 are located on the same circle and are evenly distributed on the circle. The four varistors 32 mentioned here are respectively a first varistor 321 , a second varistor 322 , a third varistor 323 and a fourth varistor 324 .

[0055] like Figure 3 As shown, in one achievable manner, the insulating layer 30 is a regular quadrilateral, which includes a first side 311, a second side 312, a third side 313 and a fourth side 314. In a preferred embodiment, the center of the circle is the intersection of the perpendicular bisector of the first side 311 and the third side 313 and the perpendicular bisector of the second side 312 and the fourth side 314.

[0056] Specifically, the uniform distribution mentioned here means that the angle formed by the orthographic projection of each two adjacent varistors 32 on the upper surface of the insulating layer 30 and the line connecting the centers of the above-mentioned circles is a right angle. Figure 3 As shown, the center of the circle is the intersection of the perpendicular bisector of the first side 311 and the third side 313 and the perpendicular bisector of the second side 312 and the fourth side 314, and the angle formed by the orthographic projection of each of the first varistor 321 and the second varistor 322 on the insulating layer 30 and the line between the intersection of the two perpendicular bisectors is a right angle. The other two adjacent varistors 32 are similar.

[0057] In a possible implementation, the SOI device layer 11 and the SOI buried oxide layer 12 form a pressure sensitive film, and the four piezoresistors 32 are located at the center positions of the four film edges of the pressure sensitive film. Figure 3 As shown, when the pressure sensitive film is projected onto the insulating layer 30, the distance a between the four piezoresistors 32 and the adjacent edges of the pressure sensitive film is a value between 0-20um, such as 0um, 5um, 10um, 15um and 20um, etc., which is not limited here. Figure 3 The distance a from the third piezoresistors 323 to the adjacent side of the pressure sensitive membrane is shown.

[0058] In a possible implementation manner, the varistor 32 is in a bent shape.

[0059] In a possible implementation, the varistor 32 includes a plurality of first resistor segments 3201 and a plurality of second resistor segments 3202. Two adjacent first resistor segments 3201 are connected via the second resistor segment 3202. The length of the first resistor segment 3201 is greater than that of the second resistor segment 3202. In addition, the extension direction of the first resistor segment 3201 is different from that of the second resistor segment 3202, that is, the connection between the first resistor segment 3201 and the second resistor segment 3202 is bent.

[0060] for example Figure 3 and Figure 4 As shown, the two second resistor segments 3202 connected to the two ends of the same first resistor segment 3201 extend toward both sides of the first resistor segment 3201 , and the first resistor segment 3201 connected to the two ends of the same second resistor segment 3202 extends toward the same side of the second resistor segment 3202 .

[0061] Preferably, the extension direction of the first resistor segment 3201 is perpendicular to the extension direction of the second resistor segment 3202. In a possible implementation, the extension direction of the first resistor segment and the extension direction of the second resistor segment may have a non-zero angle.

[0062] In a possible implementation, the first resistance segments 3201 of the four varistors 32 extend in the same direction, and the second resistance segments 3202 of the four varistors 32 extend in the same direction. That is, the first resistance segments 3201 of the first varistor 321, the second varistor 322, the third varistor 323, and the fourth varistor 324 extend in the same direction. The second resistance segments 3202 of the first varistor 321, the second varistor 322, the third varistor 323, and the fourth varistor 324 also extend in the same direction.

[0063] For example, Figure 3As shown, in one possible implementation, the extension direction of the first resistance segment 3201 of the first varistor 321, the second varistor 322, the third varistor 323 and the fourth varistor 324 is parallel to the second side 312 and the fourth side 314. The extension direction of the second resistance segment 3202 of the first varistor 321, the second varistor 322, the third varistor 323 and the fourth varistor 324 is also the same. Of course, in another possible implementation, the extension direction of the first resistance segment 3201 of the first varistor 321, the second varistor 322, the third varistor 323 and the fourth varistor 324 may also be parallel to the first side 311 and the third side 313. Of course, in some other possible implementations, the extension direction of the first resistance segment (or the second resistance segment) of at least one of the four varistors is different from the extension direction of the first resistance segment (or the second resistance segment) of the other varistors.

[0064] With respect to the implementation embodiment in which the extension direction of the first resistance segment (or second resistance segment) of at least one of the four piezoresistors is different from the extension direction of the first resistance segment (or second resistance segment) of other piezoresistors, the first resistance segments 3201 of the four piezoresistors 32 here have the same extension direction, and the second resistance segments 3202 of the four piezoresistors 32 have the same extension direction, which is more conducive to improving the overall symmetry of the piezoresistive MEMS pressure sensor, thereby improving the performance of the piezoresistive MEMS pressure sensor.

[0065] In one possible implementation, the resistance values ​​of the four varistors 32 are consistent. Figure 3 As shown, each varistor 32 can be configured to have the same bending shape, that is, to have the same first resistor segment 3201 and the same second resistor portion 322 and the same connection relationship. Figure 4 As shown, taking the second varistor 322 as an example, the bent structure in the dotted frame 320 represents the varistor. The connection between each two resistance segments of the plurality of first resistance segments 3201 and second resistance segments 3202 of the varistor 322 is defined as a bent portion. Figure 4 The dotted frame 320 includes ten bending portions, namely, a first bending portion 3211, a second bending portion 3212, a third bending portion 3213, and a fourth bending portion 3214. The first varistor 321, the third varistor 323, and the fourth varistor 324 have the same structure. Preferably, the number of bending portions of the varistor 32 is an even number.

[0066] In order to ensure the symmetry of the overall structure in this embodiment, the lengths of the first resistance segments 3201 are the same, and the lengths of the second resistance segments 3202 are also the same.

[0067] In this embodiment, the glue layer disposed on the upper surface of the insulating layer 30 is etched by a precise RIE dry etching scheme to reduce the thickness of the four varistors 32, so that the thickness of the varistors 32 ranges from Optionally, the thickness of the varistor 32 is and In addition, the line width of the varistor 32 is reduced, so that the line width range of the varistor 32 is 0-15um. Optionally, the line width of the varistor 32 is 2um, 5um, 8um, 10um and 15um. Of course, the width range of the horizontal cross-section between the varistors 32 is less than or equal to 0.02um to ensure the uniformity of the size of the varistor 32. For example, the width of the horizontal cross-section of one varistor 32 is 5.01um, and the width of the horizontal cross-section of the other varistor 32 is 4.99um, so the width range of the horizontal cross-section between the two varistors 32 is 0.02um.

[0068] The above-mentioned precise RIE dry etching improves the dimensional accuracy of the varistor 32, thereby improving the performance of the sensor, simplifying the sensor manufacturing process and reducing the cost; and realizing a small thickness, small line width and high uniformity resistance bridge structure. However, the thickness, line width and width of the horizontal cross section of the varistor 32 after etching are not limited to this, and can be adjusted in combination with the use requirements of the product.

[0069] In a possible implementation, the insulating layer 30 is SiO 2 One or a combination of layer, Si N layer or Glass layer.

[0070] In a possible implementation, the material of the lead 33 and the pad 34 is Al, Ti / Al, Au or Cr / Au. By using the above low resistivity materials, a good circuit path can be formed.

[0071] In addition, the connection between the varistors 32 through the metal leads 33 in the above embodiment can reduce the negative piezoresistive effect; and the symmetrical design structure of the metal pads 34 can improve the sensor performance.

[0072] In one possible implementation, the varistor 32 is a metal film. For example, the material of the varistor 32 is NiCr, Pt, FeN i, TiB, TaN or TiN. The material used for the varistor 32 has a high piezoresistive strain coefficient, a low noise factor and a low resistance temperature coefficient; compared with the doped silicon resistor, the noise of the pressure sensor can be significantly reduced.

[0073] In one possible implementation, refer to Figure 2As shown, the piezoresistive MEMS pressure sensor also includes a substrate 20, the upper surface of which is provided with a second bonding seed metal layer 21 and a second eutectic solder 22 in sequence from bottom to top; the lower surface of the corresponding pressure sensor sheet 10 is provided with a first bonding seed metal layer 14 and a first eutectic solder 15 in sequence from top to bottom; wherein the first bonding seed metal layer 14 and the second bonding seed metal layer 21 are eutectically bonded together by the first eutectic solder 15 and the second eutectic solder 22. In this embodiment, eutectic bonding replaces the anodic bonding method to reduce the bonding temperature and the complexity of the bonding process, so as to improve the yield rate of the piezoresistive MEMS pressure sensor.

[0074] It should be noted that, in this embodiment, by arranging two eutectic solders: the first eutectic solder 15 and the second eutectic solder 22, on the one hand, the height of the entire piezoresistive MEMS pressure sensor can be increased or adjusted to meet the design requirements; on the other hand, the deformation amount borne by the entire pressure sensor can be reduced. In this embodiment, the thickness of the first eutectic solder 15 and the second eutectic solder 22 is 10-60um, which can be 10um, 15um, 25um, 30um and 60um, etc., and the specific thickness is not limited here.

[0075] Of course, in another achievable manner, only one piece of eutectic solder may be provided for bonding the first bonding seed metal layer 14 and the second bonding seed metal layer 21. When the sensor is actually produced, the height and other dimensions of the eutectic solder may be adjusted according to the use requirements, and the specific dimensions are not limited here.

[0076] In one possible implementation, refer to Figure 2 and Figure 5 As shown, the pressure sensor sheet 10 includes, from top to bottom, an SOI device layer 11, an SOI buried oxide layer 12 and an SOI base layer 13, and a first cavity 131 is formed on the lower surface of the SOI base layer 13 by etching; a second cavity 26 communicating with the base 20 is provided on the second bonding seed metal layer 21 and the second eutectic solder 22, and a getter 23 is also provided on the upper surface of the base 20, and the getter 23 is accommodated in the second cavity 26.

[0077] When the first eutectic solder 15 and the second eutectic solder 22 are eutectically bonded together, the position of the getter 23 corresponds to the first cavity 131. The getter 23 can improve the vacuum degree in the first cavity 131 in a short time and maintain a certain vacuum degree when the pressure sensor is working.

[0078] Absolute pressure sensors and gauge pressure sensors are common types of pressure sensors. In the above embodiment, the pressure value relative to vacuum is measured to feedback the pressure, which is an absolute pressure sensor. In another possible implementation method, the pressure value relative to atmospheric pressure can also be measured to feedback the pressure, which is a gauge pressure sensor.

[0079] Specifically, Figure 7 As shown, a vent hole 25 is provided on the substrate 20; preferably, the vent hole 25 is provided at the center of the substrate 20. When the first eutectic solder 15 and the second eutectic solder 22 are eutectically bonded together, the first cavity 131 is connected to the external atmosphere through the vent hole 25. The size of the vent hole 25 is a value between 0-100um, such as 10um, 30um, 40um, 50um and 100um, etc., and the size mentioned here refers to the inner diameter of the vent hole 25.

[0080] In the above embodiment, the first cavity 131 is a square cavity, and the side length of the cavity is 500-2000um; for example, 500um, 1000um, 1200um, 1500um and 2000um, etc., and the specific side length is not limited here. Of course, the cross section of the first cavity 131 can also be set to a circular, square or other feasible shapes.

[0081] In a possible implementation, the first bonding seed metal layer 14 and the second bonding seed metal layer 21 are Cr / Au layers, Ti / Cr / Au layers or Cr / Ni / Au layers. In a possible implementation, the first eutectic solder 15 and the second eutectic solder 22 are AuSn, AgSn, CuSn or SnAgCu solder to reduce the temperature required for solder eutectic bonding.

[0082] In order to improve the bonding effect when the first bonding seed metal layer 14 and the second bonding seed metal layer 21 are eutectically bonded together through the first eutectic solder 15 and the second eutectic solder 22; in a possible implementation method, as Figure 4-5 As shown, the size of the first eutectic solder 15 is smaller than or equal to the size of the first bonding seed metal layer 14; the size of the second eutectic solder 22 is smaller than or equal to the size of the second bonding seed metal layer 21. The advantage of this design is to prevent the first eutectic solder 15 and the second eutectic solder 22 from overflowing and flowing out during bonding, thereby affecting the bonding effect.

[0083] In a possible implementation, the first bonding seed metal layer 14 has the same size as the second bonding seed metal layer 21, and when the first eutectic solder 15 and the second eutectic solder 22 are eutectically bonded together, the first bonding seed metal layer 14 corresponds to the second bonding seed metal layer 21. The advantage of such a design is that the bonding surfaces of the first bonding seed metal layer 14 and the second bonding seed metal layer 21 are ensured to be one-to-one symmetrical, which facilitates bonding alignment and improves stability after bonding.

[0084] In one possible implementation, Figure 5 As shown, there is a gap between the second outer edge 141 of the first bonding seed metal layer 14 and the first outer edge 16 of the pressure sensing sheet 10, and there is a gap between the second inner edge 142 of the first bonding seed metal layer 14 and the first inner edge 17 of the pressure sensing sheet 10, that is, there is a gap between the second inner edge of the first bonding seed metal layer 14 and the edge of the first cavity 131. The advantage of this design is that on the one hand, it can save the material of the first bonding seed metal layer 14 and save costs; on the other hand, it further limits the size of the first eutectic solder 15, because the size of the first eutectic solder 15 needs to be less than or equal to the size of the first bonding seed metal layer 14, so as to avoid the first eutectic solder 15 overflowing and flowing out during bonding, affecting the bonding effect. Therefore, when the first bonding seed metal layer 14 becomes smaller, the size of the corresponding first eutectic solder 15 also becomes smaller synchronously.

[0085] In one possible implementation, Figure 6 As shown, there is a gap between the third outer edge 211 of the second bonding seed metal layer 21 and the fifth outer edge 24 of the substrate 20; there is a gap between the fourth outer edge 261 of the second cavity 26 and the third inner edge 212 of the second bonding seed metal layer 21. The advantage of this design is that on the one hand, it can save the material of the second bonding seed metal layer 21 and save costs; on the other hand, it further limits the size of the second eutectic solder 22, because the size of the second eutectic solder 22 needs to be less than or equal to the size of the second bonding seed metal layer 21, so as to avoid the second eutectic solder 22 overflowing and flowing out during bonding, affecting the bonding effect and the normal use of the getter 23. Therefore, when the second bonding seed metal layer 21 becomes smaller, the size of the corresponding second eutectic solder 22 also becomes smaller synchronously.

[0086] In one possible implementation, the gap between the fourth outer edge 261 of the second cavity 26 and the third inner edge 212 of the second bonding seed metal layer 21 is greater than 100um, thereby preventing the overflowed second eutectic solder 22 during bonding from contacting the getter 23 and affecting the operation of the getter 23.

[0087] It should be noted that in the accompanying drawings, the sizes of layers and regions may be exaggerated for clarity of illustration. It is also understood that when an element or layer is referred to as being "on" another element or layer, it may be directly on the other element, or there may be an intermediate layer. In addition, it is understood that when an element or layer is referred to as being "under" another element or layer, it may be directly under the other element, or there may be more than one intermediate layer or element. In addition, it is also understood that when a layer or element is referred to as being "between" two layers or two elements, it may be the only layer between the two layers or two elements, or there may also be more than one intermediate layer or element. Similar reference numerals throughout the text indicate similar elements.

[0088] Those skilled in the art will readily appreciate other embodiments of the specification after considering the specification and practicing the utility model claimed herein. The specification is intended to cover any variations, uses or adaptations of the specification that follow the general principles of the specification and include common knowledge or customary techniques in the art that are not claimed in the specification. The specification and examples are to be considered exemplary only, and the true scope and spirit of the specification are indicated by the following claims.

[0089] It should be understood that the present description is not limited to the precise structures that have been described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present description is limited only by the appended claims.

[0090] The above description is only a preferred embodiment of this specification and is not intended to limit this specification. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this specification should be included in the scope of protection of this specification.

Claims

1. A piezoresistive MEMS pressure sensor, characterized in that: It comprises an insulating layer, wherein a pressure-sensitive film is arranged on the upper surface of the insulating layer, and a pressure-sensing sheet is arranged on the lower surface; wherein a lead and a varistor are arranged on the surface of the pressure-sensitive film, and the lead and the varistor are electrically connected; and the varistor is a metal film.

2. The piezoresistive MEMS pressure sensor according to claim 1, characterized in that: The thickness range of the varistor is 3. The piezoresistive MEMS pressure sensor according to claim 2, characterized in that: The thickness of the varistor is 4. The piezoresistive MEMS pressure sensor according to claim 1, characterized in that: The line width of the varistor is in the range of 0-15 um.

5. The piezoresistive MEMS pressure sensor according to claim 4, characterized in that: The line width of the varistor is 5 um.

6. The piezoresistive MEMS pressure sensor according to claim 1, characterized in that: The width difference of the horizontal cross section between the varistors is less than or equal to 0.02 um.

7. The piezoresistive MEMS pressure sensor according to claim 1, characterized in that: The material of the varistor is NiCr, Pt, FeNi, TiB, TaN or Ti N; the insulating layer is one or a combination of SiO2 layer, SiN layer or Glass layer; the material of the lead is Al, Ti / Al, Au or Cr / Au.

8. The piezoresistive MEMS pressure sensor according to claim 1, characterized in that: There are four varistors, and the orthographic projections of the four varistors on the upper surface of the insulating layer are located on the same circle and are evenly distributed on the circle.

9. The piezoresistive MEMS pressure sensor according to claim 1, characterized in that: The varistor is in a bent shape.

10. The piezoresistive MEMS pressure sensor according to claim 9, characterized in that: The varistor includes a plurality of first resistance segments and a plurality of second resistance segments, two adjacent first resistance segments are connected via the second resistance segment, the length of the first resistance segment is greater than the second resistance segment, and the extension direction of the first resistance segment is different from the extension direction of the second end.

11. The piezoresistive MEMS pressure sensor according to claim 10, characterized in that: The first resistance sections of the four varistors extend in the same direction, and the second resistance sections of the four varistors extend in the same direction.

12. The piezoresistive MEMS pressure sensor according to claim 1, characterized in that: The piezoresistive MEMS pressure sensor also includes a substrate, an upper surface of which is provided with a second bonding seed metal layer and a second eutectic solder in sequence from bottom to top; and a lower surface of the corresponding pressure sensing sheet is provided with a first bonding seed metal layer and a first eutectic solder in sequence from top to bottom; The first bonding seed metal layer and the second bonding seed metal layer are eutectic bonded together by the first eutectic solder and the second eutectic solder.

13. The piezoresistive MEMS pressure sensor according to claim 12, characterized in that: The pressure sensor sheet includes, from top to bottom, an SOI device layer, an SOI buried oxide layer and an SOI base layer, and a first cavity is formed on the lower surface of the SOI base layer by etching; a second cavity connected to the base is provided on the second bonding seed metal layer and the second eutectic solder, and a getter is provided on the upper surface of the base, and the getter is arranged in the second cavity; Wherein, when the first eutectic solder and the second eutectic solder are eutectically bonded together, the position of the getter corresponds to the first cavity.

14. The piezoresistive MEMS pressure sensor according to claim 12, characterized in that: The first bonding seed metal layer and the second bonding seed metal layer are Cr / Au layer, Ti / Cr / Au layer or Cr / Ni / Au layer; the first eutectic solder and the second eutectic solder are AuSn, AgSn, CuSn or SnAgCu solder.

15. The piezoresistive MEMS pressure sensor according to claim 12, characterized in that: The size of the first eutectic solder is smaller than or equal to the size of the first bonding seed metal layer; the size of the second eutectic solder is smaller than or equal to the size of the second bonding seed metal layer; The first bonding seed metal layer and the second bonding seed metal layer have the same size; Wherein, when the first eutectic solder and the second eutectic solder are eutectic bonded together, the first bonding seed metal layer corresponds to the second bonding seed metal layer in position.

16. The piezoresistive MEMS pressure sensor according to claim 13, characterized in that: There is a gap between the second outer edge of the first bonding seed metal layer and the first outer edge of the pressure sensing sheet, and there is a gap between the second inner edge of the first bonding seed metal layer and the first inner edge of the pressure sensing sheet; There is a gap between the third outer edge of the second bonding seed metal layer and the fifth outer edge of the substrate; there is a gap between the fourth outer edge of the second cavity and the third inner edge of the second bonding seed metal layer.

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