A MEMS pressure sensor and a method of manufacturing the same

Abstract

Disclosed are a MEMS pressure sensor and a preparation method thereof. The MEMS pressure sensor comprises: a substrate; an infrared light source located on the substrate; a thermocouple structure located on the substrate and separated from the infrared light source; a bonding layer located on the medium layer and surrounding the infrared light source and the thermocouple structure; a reflecting layer located on the surface of the bonding layer away from the medium layer; and a pressure sensing layer located on the surface of the reflecting layer away from the bonding layer, used for sensing pressure and causing the reflecting layer to deform when subjected to force; wherein the inner surface of the bonding layer and the surface of the reflecting layer opposite to the medium layer constitute a reflecting surface, and infrared light emitted by the infrared light source is reflected to the thermocouple structure through the reflecting layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a MEMS pressure sensor and a preparation method thereof. BACKGROUND

[0002] MEMS devices are microelectromechanical devices fabricated using microfabrication processes based on microelectronics technology, which have been widely used as sensors and actuators. For example, MEMS devices can be pressure sensors, accelerometers, gyroscopes, silicon condenser microphones.

[0003] Traditional MEMS pressure sensors are usually piezoresistive MEMS pressure sensors and capacitive MEMS pressure sensors. During the measurement process, there is usually a parasitic problem, which affects the sensitivity of the measurement. SUMMARY

[0004] In view of the above problems, the purpose of the present application is to provide a MEMS pressure sensor and a preparation method thereof, which uses a thermoelectric structure and an infrared light source instead of traditional piezoresistive MEMS pressure sensors and capacitive MEMS pressure sensors, thereby reducing parasitic and improving sensitivity.

[0005] The first aspect of the present application provides a MEMS pressure sensor, comprising:

[0006] a substrate;

[0007] an infrared light source located on the substrate;

[0008] a thermoelectric structure located on the substrate, which is separated from the infrared light source;

[0009] a bonding layer located on the dielectric layer, surrounding the infrared light source and the thermoelectric structure; a reflective layer located on the surface of the bonding layer away from the dielectric layer; and

[0010] a pressure sensing layer located on the surface of the reflective layer away from the bonding layer, for sensing pressure and deforming the reflective layer when subjected to force;

[0011] wherein the inner surface of the bonding layer and the surface of the reflective layer opposite to the dielectric layer form a reflecting surface, and the infrared light emitted by the infrared light source is reflected by the reflective layer to the thermoelectric structure.

[0012] In some embodiments, a dielectric layer is further included, which is located on the first surface of the substrate, the thermoelectric structure is embedded in the dielectric layer, the infrared light source is located in the dielectric layer and exposed to the surface of the dielectric layer away from the substrate.

[0013] In some embodiments, the medium layer comprises a first medium layer and a second medium layer stacked, the first medium layer is on the first surface of the substrate, and the second medium layer is on the surface of the first medium layer.

[0014] In some embodiments, the contact metal extends from the second surface of the substrate towards the second medium layer, penetrating the substrate and the first medium layer, and stopping inside the second medium layer.

[0015] In some embodiments, the thermoelectric structure comprises a plurality of thermocouples and a plurality of first metal connecting lines, the first metal connecting lines sequentially connect a plurality of mutually separated thermocouples in head-to-tail order, so that the plurality of thermocouples are connected in series to form a thermoelectric structure.

[0016] In some embodiments, the two ends of the series-connected thermocouples are connected to the corresponding contact metal via the first metal connecting line.

[0017] In some embodiments, the infrared light source is connected to the corresponding contact metal via a second metal connecting line.

[0018] In some embodiments, a pad is included, the pad is on the second surface of the substrate, and the pad is electrically connected to the corresponding contact metal.

[0019] In some embodiments, the first medium layer is a silicon oxide layer, and the second medium layer is a silicon nitride layer.

[0020] In some embodiments, the thermoelectric structure comprises a plurality of groups, and the plurality of groups of thermoelectric structures surround the infrared light source.

[0021] In some embodiments, the substrate has a back cavity, and the back cavity penetrates the substrate.

[0022] The second aspect of the present application provides a preparation method of a MEMS pressure sensor, comprising:

[0023] forming a thermoelectric structure and an infrared light source on a substrate, the thermoelectric structure and the infrared light source being mutually separated;

[0024] forming a first bonding layer on the substrate, the first bonding layer surrounding the infrared light source and the thermoelectric structure;

[0025] forming a reflective layer and a second bonding layer in sequence on the pressure sensing layer;

[0026] bonding the first bonding layer and the second bonding layer together to form the bonding layer;

[0027] The inner surface of the bonding layer and the surface of the reflecting layer opposite to the medium layer constitute a reflecting surface, infrared light emitted by the infrared light source is reflected by the reflecting layer to the thermoelectric structure, and the pressure sensing layer is used for sensing pressure and deforming the reflecting layer when stressed.

[0028] In some embodiments, the method further comprises forming a medium layer on the first surface of the substrate, the thermoelectric structure is embedded in the medium layer, and the infrared light source is located in the medium layer and exposed to the surface of the medium layer away from the substrate.

[0029] In some embodiments, the method of forming the medium layer comprises:

[0030] forming a first medium layer on the substrate; and

[0031] forming a first layer of a second medium layer on the first medium layer.

[0032] In some embodiments, the method further comprises forming a contact metal after forming the first layer of the second medium layer.

[0033] In some embodiments, the step of forming the contact metal comprises:

[0034] forming a first contact hole penetrating through the substrate, the first medium layer, and the first layer of the second medium layer; and

[0035] filling a metal material in the first contact hole to form the contact metal.

[0036] In some embodiments, the method of forming the thermoelectric structure comprises:

[0037] forming a plurality of thermocouples separated from each other on the surface of the first layer of the second medium layer;

[0038] forming a second layer of the second medium layer with a second contact hole;

[0039] forming a plurality of first metal connection lines, each of the first metal connection lines being located on the surface of the second layer of the second medium layer and filling a corresponding second contact hole; and

[0040] forming a third layer of the second medium layer covering the first metal connection lines;

[0041] The first metal connection lines sequentially connect the plurality of thermocouples separated from each other in head-to-tail manner, so that the plurality of thermocouples are connected in series to form the thermoelectric structure.

[0042] In some embodiments, two ends of the thermocouples connected in series are connected to the corresponding contact metals via the first metal connection lines.

[0043] In some embodiments, the second metal connecting line is formed at the same time when the first metal connecting line is formed, and the infrared light source is connected to the corresponding contact metal via the second metal connecting line.

[0044] In some embodiments, the method for forming the infrared light source comprises:

[0045] forming a recess on the third layer of the second medium layer, the recess extending from the surface of the third layer of the second medium layer to the inside of the third layer of the second medium layer;

[0046] filling the recess with infrared blackbody material to form the infrared light source.

[0047] In some embodiments, a pad is formed on the second surface of the substrate at the same time when the first bonding layer is formed, and the pad is electrically connected to the corresponding contact metal.

[0048] In some embodiments, the first medium layer is a silicon oxide layer, and the first layer of the second medium layer, the second layer of the second medium layer and the third layer of the second medium layer are silicon nitride layers.

[0049] In some embodiments, the thermoelectric structure comprises a plurality of groups, and the plurality of groups of the thermoelectric structure surround the infrared light source.

[0050] In some embodiments, a back cavity is further included on the substrate, and the back cavity penetrates through the substrate.

[0051] The MEMS pressure sensor provided by the application integrates core components: a pressure sensing layer, a reflecting layer, an infrared light source and an infrared thermoelectric structure, and can be applied to traditional air pressure detection or more complex three-dimensional mechanical detection, has high measurement accuracy and fast response time.

[0052] Further, the core components of the embodiment of the application only include a pressure sensing layer, a reflecting layer, an infrared light source and an infrared thermoelectric structure, and the structure is simple and easy to implement, and wafer-level packaging is adopted to realize the miniaturization of the sensor volume.

[0053] Further, in the embodiment of the application, the infrared light source is integrated in the device, and no external auxiliary light source is needed.

[0054] Further, in the embodiment of the application, the core components of the MEMS pressure sensor, the infrared light source and the infrared thermoelectric structure, are integrated in a sealed cavity, and are not prone to air leakage, and have high reliability.

[0055] Further, in the embodiment of the present application, the MEMS pressure sensor is formed by growing silicon oxide, polysilicon, silicon nitride and metal process, the preparation process is compatible with integrated circuit process, which provides the feasibility basis for monolithic integration of MEMS pressure sensor and processing circuit, and can reduce the complexity of the process and cost. BRIEF DESCRIPTION OF DRAWINGS

[0056] The above and other objects, features and advantages of the present application will become more apparent from the following description when taken in conjunction with the accompanying drawings, in which:

[0057] Figure 1 A cross-sectional view of the MEMS pressure sensor of the embodiment of the present application is shown;

[0058] Figure 2 A top view structural schematic diagram of the MEMS pressure sensor of the embodiment of the present application is shown, which does not include a reflecting layer and a pressure sensing layer;

[0059] Figures 3a to 16a Cross-sectional views of each stage in the preparation process of the MEMS pressure sensor of the embodiment of the present application are shown;

[0060] Figures 3b to 16b Top views of each stage in the preparation process of the MEMS pressure sensor of the embodiment of the present application are shown. DETAILED DESCRIPTION

[0061] The present application will be described in more detail by referring to the attached drawings. In each of the drawings, like elements are designated by like reference numerals. Each portion in the drawings is not drawn to scale for the sake of clarity. In addition, certain well-known components are not shown.

[0062] The present application can be presented in various forms, some examples of which will be described below.

[0063] Figure 1 A cross-sectional view of the MEMS pressure sensor of the embodiment of the present application is shown, Figure 2 A top view structural schematic diagram of the MEMS pressure sensor of the embodiment of the present application is shown, which does not include a reflecting layer and a pressure sensing layer, Figure 2 The portion shown by the dashed line is buried in the medium layer; as Figure 1 and Figure 2 As shown, the MEMS pressure sensor 10 includes a substrate 110, a first medium layer 120, a second medium layer 140, a plurality of thermocouple structures 150, an infrared light source 160, a contact metal 130, a bonding layer 170, a reflecting layer 180 and a pressure sensing layer 190.

[0064] The first dielectric layer 120 is located on a first surface of the substrate 110, and the second dielectric layer 140 is located on a surface of the first dielectric layer 120 away from the substrate 110. The substrate 110 has a back cavity 101 penetrating the substrate 110 and exposing a surface of the first dielectric layer 120. In this embodiment, the substrate 110 is, for example, an N-type monocrystalline silicon substrate, and the crystal direction of the N-type monocrystalline silicon substrate is, for example, (100). The first dielectric layer 120 is, for example, a silicon oxide layer, and the second dielectric layer 140 is, for example, a silicon nitride layer.

[0065] A plurality of thermoelectric structures 150 are embedded in the second dielectric layer 140. Each of the thermoelectric structures 150 includes a plurality of thermocouples 151 and a plurality of first metal connecting lines 152. The first metal connecting lines 152 sequentially connect the thermocouples 151 in a head-to-tail manner, so that the thermocouples 151 are connected in series to form the thermoelectric structure 150. The material of the thermocouples 151 is, for example, polysilicon, and the material of the first metal connecting lines 152 is, for example, aluminum.

[0066] The infrared light source 160 extends from the surface of the second dielectric layer 140 away from the substrate 110 to the inside of the second dielectric layer 140 and stops in the second dielectric layer 140, that is, the infrared light source 160 is exposed on the surface of the second dielectric layer 140 away from the substrate 110. The material of the infrared light source 160 is an infrared blackbody material (such as tungsten, nickel-chromium, etc.).

[0067] Further, a plurality of thermoelectric structures 150 surround the infrared light source 160. In a specific embodiment, the substrate 110, the first dielectric layer 120, and the second dielectric layer 140 are all rectangular, and the infrared light source 160 is located in the central region of the second dielectric layer 140. The MEMS pressure sensor 10 includes four groups of thermoelectric structures 150, and each of the thermoelectric structures 150 is located at one side of the second dielectric layer 140.

[0068] The contact metal 130 extends from the second surface of the substrate 110 (the first surface and the second surface of the substrate 110 are opposite to each other) to the second dielectric layer 140, penetrates the substrate 110 and the first dielectric layer 120, and stops in the second dielectric layer 140. The contact metal 130 is used to realize the conductive connection between the thermoelectric structure 150 and the infrared light source 160 and the outside.

[0069] Specifically, the contact metal 130 includes a first contact metal 131 and a second contact metal 132 separated from each other. The thermocouples 151 of each group of the thermoelectric structure 150 are connected to the first contact metal 131 via a first metal connecting line 152, and are electrically connected to the outside via the first contact metal 131. The infrared light source 160 is connected to the second contact metal 132 via a second metal connecting line 161, and is electrically connected to the outside via the second contact metal 132.

[0070] Further, the contact metal 130 exposed on the second surface of the substrate 110 is connected with a pad 130a, respectively.

[0071] The bonding layer 170 is located on the surface of the second medium layer 140, and the reflecting layer 180 is located on the surface of the bonding layer 170 away from the second medium layer 140. The bonding layer 170 is hollow inside, and the inner surface of the bonding layer 170 and the surface of the reflecting layer 180 opposite to the second medium layer 140 define a cavity 102, which provides a space for the infrared light 160 to propagate.

[0072] Further, the bonding layer 170 and the reflecting layer 180 are made of the same material, for example, both are gold material layers. The inner surface of the bonding layer 170 and the surface of the reflecting layer 180 opposite to the second medium layer 140 serve as a reflecting surface of the infrared light source 160. The light emitted by the infrared light source 160 is reflected to the thermoelectric structure 150 via the reflecting surface.

[0073] The pressure sensing layer 190 is located on the surface of the reflecting layer 180 away from the bonding layer, and is used to sense the external pressure.

[0074] The MEMS pressure sensor of the embodiment of the present application integrates the core components: the pressure sensing layer 190, the reflecting layer 180, the infrared light source 160, and the infrared thermoelectric structure 150, and can be applied to traditional air pressure detection or more complex three-dimensional mechanical detection. Specifically, the infrared light emitted by the infrared light source 160 irradiates the reflecting layer 180, and is reflected to the infrared thermoelectric structure 150 via the reflecting layer 180. When the pressure sensing layer 190 deforms under external force, the reflecting layer 180 deforms together with the pressure sensing layer 190, the optical path of the infrared light received by the thermoelectric structure 150 changes, and then the size of the output voltage of the infrared thermoelectric structure 150 can be measured to sense the air pressure or three-dimensional vector mechanical parameters. Compared with the traditional piezoresistive pressure sensor or the capacitive pressure sensor, the pressure sensor of the present application has higher measurement accuracy and faster response time.

[0075] Furthermore, the core components of this embodiment of the invention only include a pressure sensing layer, a reflective layer, an infrared light source, and an infrared thermopile structure, which are simple in structure, easy to implement, and adopt wafer-level packaging, which can realize the miniaturization of the sensor size.

[0076] Furthermore, in this embodiment of the invention, the infrared light source is integrated inside the device, eliminating the need for an external auxiliary light source.

[0077] Furthermore, in this embodiment of the invention, the core components of the MEMS pressure sensor, namely the infrared light source and the infrared thermopile structure, are integrated into a sealed cavity, which is not prone to leakage and has high reliability.

[0078] Furthermore, in this embodiment of the invention, the fabrication process of the MEMS pressure sensor is compatible with the integrated circuit process, providing a feasible basis for realizing the monolithic integration of the MEMS pressure sensor and the processing circuit, while reducing the complexity of the process and lowering the cost.

[0079] Figures 3a to 16a Cross-sectional views of various stages in the fabrication process of the MEMS pressure sensor according to an embodiment of the present invention are shown. Figures 3b to 16b The diagram shows a top view of each stage in the fabrication process of the MEMS pressure sensor according to an embodiment of the present invention, wherein... Figures 3a to 15a for Figures 3b to 15b Cross-sectional view along the AA direction. The following will combine... Figures 3a to 15a as well as Figures 3b to 15b The fabrication process of the MEMS pressure sensor according to an embodiment of the present invention will be described.

[0080] like Figure 3a and Figure 3b As shown, a substrate 110 is provided, and a first dielectric layer 120 and a first second dielectric layer 141 are sequentially formed on a first surface of the substrate 110.

[0081] In this embodiment, the substrate 110 is, for example, an N-type single-crystal silicon substrate, and the crystal orientation of the N-type single-crystal silicon substrate is, for example, (100). The first dielectric layer 120 is, for example, a silicon oxide layer, and the first dielectric layer 141 is, for example, a silicon nitride layer.

[0082] like Figure 4a and Figure 4b As shown, the first layer, the second layer, the second dielectric layer 141, the first dielectric layer 120, and the substrate 110 are etched to form a first contact hole 110a in the first layer, the second layer, the second dielectric layer 141, the first dielectric layer 120, and the substrate 110.

[0083] In this step, a photoresist layer is formed on the surface of the first layer second dielectric layer 141, the photoresist layer is patterned by a photolithography process to form a photoresist mask, and the first layer second dielectric layer 141, the first dielectric layer 120 and the substrate 110 are etched through the photoresist mask to form the first contact hole 110a. The first contact hole 110a penetrates through the first layer second dielectric layer 141, the first dielectric layer 120 and the substrate 110.

[0084] As shown in Figure 5a and Figure 5b , the first contact hole 110a is filled with a conductive material to form a contact metal 130.

[0085] In this step, the first contact hole 110a is filled with a conductive material by a deposition process, and the conductive material outside the first contact hole 110a is polished by a polishing process, so that the conductive material only fills inside the first contact hole 110a, thereby forming the contact metal 130. The contact metal 130 is exposed to the second surface of the substrate 110 (the first surface and the second surface of the substrate 110 are opposite) and the surface of the first layer second dielectric layer 141. The contact metal 130 includes a first contact metal 131 and a second contact metal 132 which are separated from each other.

[0086] As shown in Figure 6a and Figure 6b , a thermocouple 151 is formed on the surface of the first layer second dielectric layer 141.

[0087] In this step, a polysilicon layer is formed on the surface of the first layer second dielectric layer 141 and the surface of the contact metal 131 by a deposition process, and then the polysilicon layer is patterned by a photolithography process and an etching process to form the thermocouple 151. The thermocouple 151 includes a plurality of thermocouples 151 which are separated from each other, and each thermocouple 151 is not in contact with the contact metal 131 exposed on the surface of the first layer second dielectric layer 141.

[0088] As shown in Figure 7a and Figure 7b , a second layer second dielectric layer 142 with a second contact hole 142a is formed.

[0089] In the step, a second layer of second medium layer 142 is formed on the surface of the first layer of second medium layer 141 by using a deposition process. The second layer of second medium layer 142 covers the surface of the first layer of second medium layer 141, the surface of the contact metal 131 and the surface of the thermocouple 151 and the sidewall. Then, the second layer of second medium layer 142 is patterned by using a photolithography process to form a second contact hole 142a in the second layer of second medium layer 142. The second contact hole 142a penetrates the second layer of second medium layer 142 to expose the surface of the contact metal 130 and part of the surface of the thermocouple 151. In the embodiment, the second layer of second medium layer 142 is a silicon nitride layer.

[0090] As shown in Figure 8a and Figure 8b , a first metal connecting line 152 and a second metal connecting line 161 are formed.

[0091] In the step, a conductive metal material is formed on the surface of the second layer of second medium layer 142 by using a deposition process. The conductive metal material covers the surface of the second layer of second medium layer 142 and fills the second contact hole 142a. Then, the conductive metal layer is patterned by using a photolithography process and an etching process to form the first metal connecting line 152 and the second metal connecting line 161.

[0092] The first metal connecting line 152 connects a plurality of thermocouples 151 in series and connects both ends of the series-connected thermocouples 151 to the corresponding first contact metal 131, respectively. The first metal connecting line 152 and the thermocouple 151 form a thermoelectric stack structure 150. In the embodiment, four groups of thermoelectric stack structures 150 are included. The substrate 110 is rectangular. The four groups of thermoelectric stack structures 150 are arranged at four side edges of the substrate 110, respectively, to surround a light source to be formed later. The second metal connecting line 161 is used to connect the light source to be formed later to the second contact metal 132.

[0093] As shown in Figure 9a and Figure 9b , a third layer of second medium layer 143 is formed.

[0094] In the step, a third layer of second medium layer 143 is formed on the surface of the second layer of second medium layer 142. The third layer of second medium layer 143 covers the surface of the second layer of second medium layer 142, the first metal connecting line 152 and the second metal connecting line 161. The third layer of second medium layer 143 is a silicon nitride layer. The first layer of second medium layer 141, the second layer of second medium layer 142 and the third layer of second medium layer 143 form a second medium layer 140.

[0095] Figure 10a Figure 10b As shown in FIG. 16, an infrared light source 160 is formed in the third layer of second dielectric layer 143.

[0096] In this step, a groove is formed in the third layer of second dielectric layer 143, which extends from the surface of the third layer of second dielectric layer 143 to the substrate 110. Then, an infrared blackbody material (such as tungsten, nickel-chromium, etc.) is filled in the groove, and the infrared blackbody material is patterned to form the infrared light source 160 in the groove. The infrared light source 160 is in contact with the second metal connecting line 161, and is connected to the second contact metal 132 via the second metal connecting line 161.

[0097] Figure 11a Figure 11b As shown in FIG. 17, a first bonding layer 171 is formed on the surface of the third layer of second dielectric layer 143, and a pad 130a is formed on the surface of the substrate 110 away from the dielectric layer 120.

[0098] In this step, a metal material layer is formed on the surface of the third layer of second dielectric layer 143 and the surface of the substrate 110 away from the dielectric layer 120 by, for example, a deposition process. Then, the metal material layer is patterned by, for example, a photolithography and etching process to form the first bonding layer 171 on the surface of the third layer of second dielectric layer 143, and a plurality of mutually separated pads 130a on the surface of the substrate 110 away from the dielectric layer 120. The first bonding layer 171 is located at the edge of the dielectric layer 140, and surrounds the thermoelectric structure 150 and the infrared light source 160. The plurality of pads 130a are in contact with the contact metal 130 exposed on the surface of the substrate 110. In this embodiment, the material of the pads 130a and the first bonding layer 171 is, for example, gold.

[0099] Figure 12a Figure 12b Figure 13a Figure 13b As shown in FIG. 18, a pressure sensing layer 190 is provided, and a reflective layer 180 is formed on the first surface of the pressure sensing layer 190. In this step, the reflective layer 180 is formed on the surface of the pressure sensing layer 190 by, for example, a deposition process. The reflective layer 180 is, for example, a gold material layer.

[0100] Figure 14a Figure 14b As shown in FIG. 19, a second bonding layer 172 is formed on the surface of the reflective layer 180.

[0101] ​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​In this step, a thick photoresist layer is formed on the surface of the reflective layer 180, and a photoetching process is performed on the back photoresist layer to form a mask layer, wherein the mask layer is located in the central region of the reflective layer 180, and exposes the peripheral edge of the surface of the reflective layer 180. Then, a second bonding layer 172 is formed on the edge of the reflective layer 180 by, for example, an electroplating process. After the formation of the second bonding layer 172, the mask layer is removed by a stripping process. The second bonding layer 172 is located on the edge of the reflective layer, corresponding to the position of the first bonding layer 171.

[0102] As shown in Figure 15a and Figure 15b The first bonding layer and the second bonding layer are combined together. Wherein the first bonding layer 171 and the second bonding layer 172 form a bonding layer 170 together, and the inner surface of the bonding layer 170 and the surface of the reflective layer 180 opposite to the second dielectric layer 140 define a sealed cavity 102, which provides a transmission space for the infrared light emitted by the infrared light source 160.

[0103] As shown in Figure 16a and Figure 16b The back cavity 101 is formed.

[0104] In this step, a resist layer is formed on the first surface of the substrate 110, a photoetching process is used to pattern the resist layer to form a resist mask, and the substrate 110 is etched through the resist mask to form the back cavity 101, thereby releasing the thermoelectric structure 150.

[0105] The MEMS pressure sensor provided by the application integrates core components: a pressure sensing layer, a reflective layer, an infrared light source, and an infrared thermoelectric structure, and can be applied to traditional air pressure detection or more complex three-dimensional mechanical detection, has high measurement accuracy, and has fast response time.

[0106] Further, the core components of the embodiment of the application only include a pressure sensing layer, a reflective layer, an infrared light source, and an infrared thermoelectric structure, and the like, and the structure is simple, easy to implement, and can realize the miniaturization of the sensor volume by using wafer-level packaging.

[0107] Further, in the embodiment of the application, the infrared light source is integrated in the device, and an external auxiliary light source is not needed.

[0108] Further, in the embodiment of the application, the core components of the MEMS pressure sensor, the infrared light source, and the infrared thermoelectric structure are integrated in a sealed cavity, and are not easy to leak air, and have high reliability.

[0109] Further, in the embodiments of the present application, the MEMS pressure sensor is formed by growing silicon oxide, polysilicon, silicon nitride and metal processes, the preparation process is compatible with integrated circuit process, which provides the feasibility basis for realizing the monolithic integration of the MEMS pressure sensor and the processing circuit, and can reduce the complexity of the process and the cost.

[0110] In accordance with the embodiments of the present application as described above, these embodiments do not describe all the details and are not limited to the specific embodiments described. Obviously, many modifications and variations can be made in light of the above description. The present description selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well utilize the present application and make modifications and uses on the basis of the present application. The present application is limited only by the claims and their full scope and equivalents.

Claims

1. A MEMS pressure sensor, comprising: a substrate; an infrared light source on the substrate; a thermopile structure on the substrate, which is separated from the infrared light source; a bonding layer on the substrate, which surrounds the infrared light source and the thermopile structure; a reflective layer on a surface of the bonding layer away from the substrate; and a pressure sensing layer on a surface of the reflective layer away from the bonding layer, which is used to sense pressure and cause the reflective layer to deform when stressed; wherein an inner surface of the bonding layer and a surface of the reflective layer opposite to the substrate form a reflective surface, and infrared light emitted by the infrared light source is reflected by the reflective layer to the thermopile structure. Further comprising a dielectric layer on a first surface of the substrate, the thermopile structure is embedded in the dielectric layer, and the infrared light source is in the dielectric layer and exposed on a surface of the dielectric layer away from the substrate. The dielectric layer comprises a first dielectric layer and a second dielectric layer stacked together, the first dielectric layer is on the first surface of the substrate, and the second dielectric layer is on a surface of the first dielectric layer. Contact metal extends from a second surface of the substrate towards the second dielectric layer, penetrates the substrate and the first dielectric layer, and stops in the second dielectric layer. The thermopile structure comprises a plurality of thermocouples and a plurality of first metal connecting lines, the first metal connecting lines sequentially connect the plurality of thermocouples in a head-to-tail manner so that the plurality of thermocouples are connected in series to form the thermopile structure. Two ends of the thermocouples connected in series are connected to corresponding contact metal via the first metal connecting lines. The infrared light source is connected to corresponding contact metal via second metal connecting lines. A pad is on the second surface of the substrate, and the pad is electrically connected to corresponding contact metal. The first dielectric layer is a silicon oxide layer, and the second dielectric layer is a silicon nitride layer.

2. The MEMS pressure sensor of claim 1, wherein, The thermopile structure comprises a plurality of groups, and the plurality of groups of thermopile structures surround the infrared light source.

3. The MEMS pressure sensor of claim 2, wherein, The substrate has a back cavity that penetrates the substrate.

4. The MEMS pressure sensor of claim 3, wherein, 12.A method for manufacturing a MEMS pressure sensor, comprising: forming a thermopile structure and an infrared light source on a substrate, the thermopile structure being separated from the infrared light source; forming a first bonding layer on the substrate, the first bonding layer surrounding the infrared light source and the thermopile structure; forming a reflective layer and a second bonding layer in sequence on a pressure sensing layer; bonding the first bonding layer and the second bonding layer together to form the bonding layer; wherein an inner surface of the bonding layer and a surface of the reflective layer opposite to the substrate form a reflective surface, infrared light emitted by the infrared light source is reflected by the reflective layer to the thermopile structure, and the pressure sensing layer is used to sense pressure and cause the reflective layer to deform when stressed.

5. The MEMS pressure sensor of claim 4, wherein, Further comprising forming a dielectric layer on a first surface of the substrate between the thermopile structure and the infrared light source, the thermopile structure is embedded in the dielectric layer, and the infrared light source is in the dielectric layer and exposed on a surface of the dielectric layer away from the substrate.

6. The MEMS pressure sensor of claim 5, wherein, ​ 7. The MEMS pressure sensor of claim 4, wherein, ​ 8. The MEMS pressure sensor of claim 4, wherein, ​ 9. The MEMS pressure sensor of claim 3, wherein, ​ 10. The MEMS pressure sensor of claim 1, wherein, ​ 11. The MEMS pressure sensor of claim 1, wherein, ​ ​ ​ ​ ​ ​ ​ 13. The method of claim 12, wherein, ​ 14. The method of claim 13, wherein, The method of forming the dielectric layer comprises: forming a first dielectric layer on the substrate; and forming a first layer of second dielectric layer on the first dielectric layer.

15. The method of claim 14, wherein, comprises: forming a contact metal after forming the first layer of second dielectric layer.

16. The method of claim 15, wherein, The step of forming the contact metal comprises: forming a first contact hole penetrating through the substrate, the first dielectric layer and the first layer of second dielectric layer; and filling a metal material in the first contact hole to form the contact metal.

17. The method of claim 15, wherein, The method of forming the thermoelectric stack structure comprises: forming a plurality of thermocouples separated from each other on a surface of the first layer of second dielectric layer; forming a second layer of second dielectric layer with a second contact hole; forming a plurality of first metal connection lines, each of the first metal connection lines being located on the surface of the second layer of second dielectric layer and filling a corresponding second contact hole; and forming a third layer of second dielectric layer covering the first metal connection lines; the first metal connection lines sequentially connecting the plurality of thermocouples separated from each other in head-to-tail manner so that the plurality of thermocouples are connected in series to form a thermoelectric stack structure.

18. The method of claim 17, wherein, Two ends of the thermocouples connected in series are connected to the corresponding contact metal via the first metal connection lines.

19. The method of claim 17, wherein, The second metal connection lines are formed at the same time when the first metal connection lines are formed, and the infrared light source is connected to the corresponding contact metal via the second metal connection lines.

20. The method of claim 17, wherein, The method of forming the infrared light source comprises: forming a recess on the third layer of second dielectric layer, the recess extending from a surface of the third layer of second dielectric layer to an inside of the third layer of second dielectric layer; filling an infrared blackbody material in the recess to form the infrared light source.

21. The method of claim 12, wherein, The pad is electrically connected to the corresponding contact metal.

22. The method of claim 17, wherein, The first dielectric layer is a silicon oxide layer, and the first layer of second dielectric layer, the second layer of second dielectric layer and the third layer of second dielectric layer are silicon nitride layers.

23. The method of claim 12, wherein, The thermoelectric stack structure comprises a plurality of groups, and the plurality of groups of thermoelectric stack structures surround the infrared light source.

24. The method of claim 12, wherein, A back cavity is further formed on the substrate, and the back cavity penetrates through the substrate.

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