CN219223988U

CN219223988U - MEMS pressure sensor

Info

Publication number: CN219223988U
Application number: CN202320470825.4U
Authority: CN
Inventors: 蔡春华; 万蔡辛; 赵成龙; 巩啸风; 何政达; 陈骁
Original assignee: Wuxi Weigan Semiconductor Co ltd
Current assignee: Wuxi Weigan Semiconductor Co ltd
Priority date: 2022-09-19
Filing date: 2023-03-13
Publication date: 2023-06-20
Anticipated expiration: 2033-03-13

Abstract

Disclosed is a MEMS pressure sensor, comprising: a substrate; a thermopile structure located on the substrate; a bonding layer on the substrate surrounding the thermopile structure; the transparent layer is positioned on the surface of the bonding layer, which is far away from the substrate, and a groove is formed in the surface of the transparent layer, which is close to the substrate, and a lens structure is arranged in the groove; the reflecting layer is positioned on the surface of the transparent layer far away from the bonding layer, and a through hole penetrating through the reflecting layer is formed in the reflecting layer; the position of the through hole corresponds to the position of the convex lens, and the through hole is used for receiving infrared light, so that the infrared light irradiates the transparent layer and then irradiates the thermopile structure through the lens structure.

Description

MEMS pressure sensor

Technical Field

The utility model relates to the technical field of semiconductors, in particular to an MEMS pressure sensor.

Background

MEMS devices are microelectromechanical devices developed on the basis of microelectronics that have been fabricated using micromachining processes, and have been widely used as sensors and actuators. For example, the MEMS device may be a pressure sensor, accelerometer, gyroscope, silicon condenser microphone.

The conventional MEMS pressure sensor is usually a piezoresistive MEMS pressure sensor and a capacitive MEMS pressure sensor, and the piezoresistive MEMS pressure sensor and the capacitive MEMS pressure sensor usually have parasitic problems in the measurement process, which affect the measurement sensitivity.

Disclosure of Invention

In view of the above problems, an object of the present utility model is to provide a MEMS pressure sensor, which adopts a thermopile structure and a lens structure, and replaces the conventional piezoresistive MEMS pressure sensor and capacitive MEMS pressure sensor, thereby reducing the parasitic and improving the sensitivity.

A first aspect of the present utility model provides a MEMS pressure sensor comprising:

a substrate;

a thermopile structure located on the substrate;

a bonding layer on the substrate surrounding the thermopile structure;

the transparent layer is positioned on the surface of the bonding layer, which is far away from the substrate, and a groove is formed in the surface of the transparent layer, which is close to the substrate, and a lens structure is arranged in the groove; and

the reflecting layer is positioned on the surface of the transparent layer far away from the bonding layer, and a through hole penetrating through the reflecting layer is formed in the reflecting layer;

the through holes are used for receiving infrared light, so that the infrared light irradiates the transparent layer and then irradiates the thermopile structure through the lens structure.

In some embodiments, the substrate has a back cavity that extends through the substrate.

In some embodiments, a dielectric layer is included on the substrate, the thermopile structure being buried within the dielectric layer.

In some embodiments, the dielectric layer includes a first dielectric layer and a second dielectric layer stacked, the first dielectric layer being located on a first surface of the substrate, the second dielectric layer being located on a surface of the first dielectric layer.

In some embodiments, a contact metal is included that extends from the second surface of the substrate toward the second dielectric layer, through the substrate and the first dielectric layer, and terminates inside the second dielectric layer.

In some embodiments, the thermopile structure comprises a plurality of thermocouples and a plurality of metal connecting wires connecting the plurality of thermocouples separated from each other in an end-to-end order such that the plurality of thermocouples are connected in series to form the thermopile structure.

In some embodiments, both ends of the thermocouples connected in series are connected to respective contact metals via the metal connection wires.

In some embodiments, a pad is included on the second surface of the substrate, the pad being in electrical connection with a corresponding contact metal.

In some embodiments, the first dielectric layer is a silicon oxide layer and the second dielectric layer is a silicon nitride layer.

In some embodiments, the bonding layer is internally hollow, and the inner surface of the bonding layer, the inner surface of the recess of the transparent layer, and the surface of the dielectric layer define a sealed cavity within which the thermopile structure and the lens structure are located.

The MEMS pressure sensor provided by the utility model integrates core components: the transparent layer, the reflecting layer, the lens structure and the infrared thermopile structure can be applied to traditional air pressure detection or more complex three-dimensional mechanical detection, and have higher measurement accuracy and quicker response time.

Furthermore, the core component of the embodiment of the utility model only comprises a transparent layer, a reflecting layer, a lens structure, an infrared thermopile structure and the like, has simple structure and easy implementation, and can realize the miniaturization of the volume of the sensor by adopting wafer-level packaging.

Further, in the embodiment of the utility model, the core component lens structure and the infrared thermopile structure of the MEMS pressure sensor are integrated in the sealed cavity, so that the MEMS pressure sensor is not easy to leak air and has high reliability.

Further, in the embodiment of the utility model, the MEMS pressure sensor is formed by growing silicon oxide, polysilicon, silicon nitride and metal, and the preparation process is compatible with the integrated circuit process, thereby providing a feasible foundation for realizing monolithic integration of the MEMS pressure sensor and the processing circuit, and simultaneously reducing the complexity of the process and the cost.

Drawings

The above and other objects, features and advantages of the present utility model will become more apparent from the following description of embodiments of the present utility model with reference to the accompanying drawings, in which:

FIG. 1 illustrates a cross-sectional view of a MEMS pressure sensor in accordance with an embodiment of the present utility model;

FIG. 2 shows a schematic top view of a MEMS pressure sensor of an embodiment of the present utility model without the reflective layer and the transparent layer;

FIGS. 3a to 16a are sectional views showing various stages in the fabrication process of a MEMS pressure sensor according to an embodiment of the present utility model;

fig. 3b to 16b show top views of various stages in the fabrication of a MEMS pressure sensor according to an embodiment of the utility model.

Detailed Description

The utility model will be described in more detail below with reference to the accompanying drawings. Like elements are denoted by like reference numerals throughout the various figures. For clarity, the various features of the drawings are not drawn to scale. Furthermore, some well-known portions may not be shown.

The utility model may be embodied in various forms, some examples of which are described below.

FIG. 1 is a cross-sectional view of a MEMS pressure sensor according to an embodiment of the present utility model, and FIG. 2 is a schematic top view of the MEMS pressure sensor according to an embodiment of the present utility model without including a reflective layer and a transparent layer, wherein a portion shown by a dotted line in FIG. 2 is buried inside the dielectric layer; as shown in fig. 1 and 2, the MEMS pressure sensor 10 includes a substrate 110, a first dielectric layer 120, a second dielectric layer 140, a plurality of sets of thermopile structures 150, a contact metal 130, a bonding layer 170, a reflective layer 180, a lens structure 191, and a transparent layer 190.

The first dielectric layer 120 is located on the first surface of the substrate 110, and the second dielectric layer 140 is located on the surface of the first dielectric layer 120 away from the substrate 110. The substrate 110 has a back cavity 101 thereon, and the back cavity 101 penetrates through the substrate 110 to expose the 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 orientation 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.

The plurality of thermopile structures 150 are embedded within the second dielectric layer 140. Each set of the thermopile structure 150 includes a plurality of thermocouples 151 and a plurality of metal connection wires 152, and the metal connection wires 152 connect the plurality of thermocouples 151 separated from each other in order from end to end, so that the plurality of thermocouples are connected in series to form the thermopile structure 150. The material of the thermocouple 151 is, for example, polysilicon, and the material of the metal connection wire 152 is, for example, metal aluminum.

In a specific embodiment, the substrate 110, the first dielectric layer 120, and the second dielectric layer 140 are rectangular, and the MEMS pressure sensor 10 includes 4 sets of thermopile structures 150, each set of thermopile structures 150 being located at one side of the second dielectric layer 140.

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) toward the second dielectric layer 140, penetrates the substrate 110 and the first dielectric layer 120, and stops inside the second dielectric layer 140. The contact metal 130 is used to realize an electrically conductive connection of the thermopile structure 150 to the outside. Both ends of the thermocouple 151 of each group of the thermopile structures 150 are connected to the contact metal 130 via metal connection wires 152, and are electrically connected to the outside via the contact metal 130. Further, the contact metals 130 exposed from the second surface of the substrate 110 are respectively connected with pads 130a.

The bonding layer 170 is located on the surface of the second dielectric layer 140, and the transparent layer 190 is located on the surface of the bonding layer 170 away from the second dielectric layer 140; the first surface of the transparent layer 190 has a recess extending from the first surface of the transparent layer 190 in a direction away from the bonding layer 170, the recess having a lens structure 191 in a central region thereof. The bonding layer 170 is hollow internally, the inner surface of the bonding layer 170 and the inner surface of the recess of the transparent layer 190 define a cavity 102, and the lens structure 191 is located in the cavity 102. In this embodiment, the lens structure 191 is, for example, a convex lens structure.

The reflective layer 180 is located on the second surface of the transparent layer 190, the reflective layer 180 has a through hole 181 therein, the through hole 181 is located in a central area of the transparent layer 190, which corresponds to the position of the lens structure 191, and the through hole 181 penetrates through the reflective layer 180 to expose the second surface of the transparent layer 190. In this embodiment, the bonding layer 170 and the reflective layer 180 are made of the same material, for example, gold material. The transparent layer 190 is, for example, a glass layer. The transparent layer 190 is used to sense external pressure.

The MEMS pressure sensor of the embodiment of the utility model integrates core components: the transparent layer 190, the lens structure 191, the reflecting layer 180 and the infrared thermopile structure 150 can be applied to conventional air pressure detection or more complex three-dimensional mechanical detection, specifically, the part of the infrared light emitted by the infrared light source 20 outside the MEMS pressure sensor, which irradiates the reflecting layer 180, the part of the infrared light irradiated by the MEMS pressure sensor reflected by the reflecting layer 180, the part irradiated by the through hole 181, the transparent layer 190, the lens structure 191, and the thermopile structure 150 are refracted by the lens structure 191; when the transparent layer 190 receives an external force to deform, the lens structure 191 deforms along with the transparent layer 190, the optical path of infrared light received by the thermopile structure 150 changes, and then the sensing air pressure or the three-dimensional vector mechanical parameter can be carried out by measuring the output voltage of the infrared thermopile structure 150.

Further, in the embodiment of the utility model, the core component lens structure 191 and the infrared thermopile structure of the MEMS pressure sensor are integrated in a sealed cavity, so that the air leakage is not easy, and the reliability is high.

Furthermore, in the embodiment of the utility model, the preparation process of the MEMS pressure sensor is compatible with the integrated circuit process, thereby providing a feasible foundation for realizing the monolithic integration of the MEMS pressure sensor and the processing circuit, and simultaneously reducing the complexity of the process and the cost.

FIGS. 3a to 16a are sectional views showing various stages in the fabrication process of a MEMS pressure sensor according to an embodiment of the present utility model; fig. 3b to 16b are top views showing various stages in the fabrication process of the MEMS pressure sensor according to the embodiment of the present utility model, wherein fig. 3a to 15a are cross-sectional views along AA direction of fig. 3b to 15 b. The MEMS pressure sensor manufacturing process according to the embodiment of the present utility model will be described with reference to fig. 3a to 15a and fig. 3b to 15 b.

As shown in fig. 3a and 3b, 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.

In this embodiment, the substrate 110 is, for example, an N-type monocrystalline silicon substrate, and the crystal orientation 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 first and second dielectric layers 141 are, for example, silicon nitride layers.

As shown in fig. 4a and 4b, the first and second

dielectric layers

141, 120 and the substrate 110 are etched, and a first contact hole 110a is formed in the first and second

dielectric layers

141, 120 and the substrate 110.

In this step, for example, a photoresist layer is formed on the surface of the first and second dielectric layers 141, the photoresist layer is patterned using a photolithography process to form a photoresist mask, and the first and second

dielectric layers

141, 120 and the substrate 110 are etched through the photoresist mask to form the first contact hole 110a. The first contact hole 110a penetrates the first second dielectric layer 141, the first dielectric layer 120, and the substrate 110.

As shown in fig. 5a and 5b, a conductive material is filled in the first contact hole 110a to form a contact metal 130.

In this step, for example, a deposition process is used to fill the conductive material inside the first contact hole 110a, and a polishing process is used to polish the conductive material outside the first contact hole 110a, so that the conductive material is only filled inside the first contact hole 110a, thereby forming the contact metal 130. The contact metal 130 is exposed to a second surface of the substrate 110 (the first and second surfaces of the substrate 110 are opposite) and to a surface of the first and second dielectric layers 141.

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

In this step, a polysilicon layer is formed on the surface of the first second dielectric layer 141 and the surface of the contact metal 131, for example, by a deposition process, and then the polysilicon layer is patterned, for example, by a photolithography process and an etching process, to form the thermocouple 151. Wherein, include a plurality of said thermocouples 151, a plurality of said thermocouples 151 are separated each other, and each said thermocouple 151 is not contacted with the contact metal 130 exposed on the surface of said first layer of second medium 141.

As shown in fig. 7a and 7b, a second dielectric layer 142 having a second contact hole 142a is formed.

In this step, a second dielectric layer 142 is formed on the surface of the first second dielectric layer 141, for example, by using a deposition process, and the second dielectric layer 142 covers the surface of the first second dielectric layer 141, the surface of the contact metal 131, and the surface and the sidewalls of the thermocouple 151. Next, the second dielectric layer 142 is patterned, for example, by using a photolithography process, so as to form a second contact hole 142a in the second dielectric layer 142. The second contact hole 142a penetrates through the second dielectric layer 142, exposing the surface of the contact metal 130 and a portion of the surface of the plurality of thermocouples 151. Wherein the second contact holes 142a are respectively positioned at the head-to-tail positions of each thermocouple. In this embodiment, the second dielectric layer 142 is, for example, a silicon nitride layer.

As shown in fig. 8a and 8b, the metal connection line 152 and the second metal connection line 161 are formed.

In this step, a conductive metal material is formed on the surface of the second dielectric layer 142, for example, by a deposition process, wherein the conductive metal material covers the surface of the second dielectric layer 142 and fills the second contact hole 142a, and then the conductive metal layer is patterned, for example, by a photolithography process and an etching process, to form

metal connection lines

152,1, each of which connects one end of one thermocouple 151 with one end of the other thermocouple 151, such that the metal connection lines 152 connect a plurality of thermocouples 151 separated from each other in series, and connect both ends of the thermocouples 151 connected in series to the corresponding contact metals 130, respectively, and the metal connection lines 152 and the thermocouples 151 constitute a thermopile structure 150.

In this embodiment, the substrate 110 includes four sets of thermopile structures 150, and the four sets of thermopile structures 150 are respectively arranged at four sides of the substrate 110.

As shown in fig. 9a and 9b, a third second dielectric layer 143 is formed.

In this step, a third second dielectric layer 143 is formed on the surface of the second dielectric layer 142, and the third second dielectric layer 143 covers the surface of the second dielectric layer 142 and the metal connection line 152. The third second dielectric layer 143 is, for example, a silicon nitride layer. Wherein the first second dielectric layer 141, the second dielectric layer 142, and the third second dielectric layer 143 constitute the second dielectric layer 140.

As shown in fig. 10a and 10b, a first bonding layer 171 is formed on the surface of the third second dielectric layer 143 and a pad 130a is formed on the surface of the substrate 110 remote from the dielectric layer 120.

In this step, a metal material layer is formed on the surface of the third second dielectric layer 143 and the surface of the substrate 110 away from the dielectric layer 120, for example, by a deposition process, and then the metal material layer is patterned, for example, by photolithography and etching processes, so as to form a first bonding layer 171 on the surface of the first dielectric layer 124, and form a plurality of mutually separated bonding pads 130a on the surface of the substrate 110 away from the dielectric layer 20, where the first bonding layer 171 is located at an edge of the dielectric layer 140 and surrounds the thermopile structure 150 and the infrared light source 160; a plurality of the pads 130a are respectively contacted with the contact metal 130 exposed from the surface of the substrate 110. In this embodiment, the pad 130a and the first bonding layer 171 are made of a material such as gold.

As shown in fig. 11a, 11b, 12a and 12b, a transparent layer 190 is provided, and a reflective layer 180 having a through hole 181 is formed on a second surface of the transparent layer 190.

In this step, the reflective layer 180 is formed on the second surface of the transparent layer 190, for example, by using a deposition process, and then the through hole 181 is formed in the reflective layer 180 by using a photolithography and etching process, and the through hole 181 is located in a central area of the reflective layer 180 and penetrates through the reflective layer 180 to expose the transparent layer 190. In this embodiment, the transparent layer 190 is, for example, a glass layer, and the reflective layer 180 is, for example, a gold layer.

As shown in fig. 13a and 13b, a second bonding layer 172 is formed on the first surface of the transparent layer 190.

In this step, a metal material layer is formed on the first surface of the transparent layer 190, for example, by using a sputtering process, then, the metal material layer is thickened, for example, by using an electroplating process, and the metal material layer is etched by using a photolithography process and an etching process, so as to form the second bonding layer 172. The second bonding layer 172 is located at an edge of the first surface of the transparent layer 190, corresponding to the position of the first bonding layer 171.

As shown in fig. 14a and 14b, the first surface of the transparent layer 190 is etched, a groove is formed on the first surface of the transparent layer 190, and a lens structure 191 is formed in a central region of the groove, the lens structure 191 corresponding to the position of the through hole 181.

As shown in fig. 15a and 15b, the first bonding layer 171 and the second bonding layer 172 are bonded together. Wherein the first bonding layer 171 and the second bonding layer 172 together form a bonding layer 170, and wherein the inner surface of the bonding layer 170 and the inner surface of the recess of the transparent layer 190 define a sealed cavity 102, and wherein the lens structure 191 is located within the cavity 102. In this embodiment, the lens structure 191 is, for example, a convex lens structure.

As shown in fig. 16a and 16b, the back cavity 101 is formed.

In this step, a resist layer is formed on the second surface of the substrate 110, the resist layer is patterned using a photolithography process to form a resist mask, and the substrate 110 is etched through the resist mask to form the back cavity 101, thereby releasing the thermopile structure 150. The back cavity 101 penetrates through the substrate 110, and exposes the surface of the first dielectric layer 120.

Embodiments in accordance with the present utility model, as described above, are not intended to be exhaustive or to limit the utility model to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the utility model and the practical application, to thereby enable others skilled in the art to best utilize the utility model and various modifications as are suited to the particular use contemplated. The utility model is limited only by the claims and the full scope and equivalents thereof.

Claims

1. A MEMS pressure sensor, comprising:

a substrate;

a thermopile structure located on the substrate;

a bonding layer on the substrate surrounding the thermopile structure;

2. The MEMS pressure sensor of claim 1, wherein the substrate has a back cavity extending through the substrate.

3. The MEMS pressure sensor of claim 1, comprising a dielectric layer on the substrate, the thermopile structure being embedded within the dielectric layer.

4. The MEMS pressure sensor of claim 3, wherein the dielectric layer comprises a first dielectric layer and a second dielectric layer stacked, the first dielectric layer being located on a first surface of the substrate, the second dielectric layer being located on a surface of the first dielectric layer.

5. The MEMS pressure sensor of claim 4, comprising a contact metal extending from the second surface of the substrate toward the second dielectric layer, through the substrate and the first dielectric layer, and terminating inside the second dielectric layer.

6. The MEMS pressure sensor of claim 5, wherein the thermopile structure comprises a plurality of thermocouples and a plurality of metal connection wires connecting the plurality of thermocouples separated from each other in an end-to-end order such that the plurality of thermocouples are connected in series to form the thermopile structure.

7. The MEMS pressure sensor of claim 6, wherein both ends of the series of thermocouples are connected to respective contact metals via the metal connection wires.

8. The MEMS pressure sensor of claim 5, comprising pads located on the second surface of the substrate, the pads being electrically connected to respective contact metals.

9. The MEMS pressure sensor of claim 4, wherein the first dielectric layer is a silicon oxide layer and the second dielectric layer is a silicon nitride layer.

10. The MEMS pressure sensor of claim 3, wherein the bonding layer is internally hollow, an inner surface of the bonding layer, an inner surface of the recess of the transparent layer, and a surface of the dielectric layer define a sealed cavity, the thermopile structure and the lens structure being located within the cavity.