CN115420408A - MEMS pressure sensor and preparation method thereof - Google Patents
MEMS pressure sensor and preparation method thereof Download PDFInfo
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- CN115420408A CN115420408A CN202211138067.2A CN202211138067A CN115420408A CN 115420408 A CN115420408 A CN 115420408A CN 202211138067 A CN202211138067 A CN 202211138067A CN 115420408 A CN115420408 A CN 115420408A
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- 238000004519 manufacturing process Methods 0.000 claims abstract description 10
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- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical group N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 10
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/24—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet
- G01L1/248—Measuring force or stress, in general by measuring variations of optical properties of material when it is stressed, e.g. by photoelastic stress analysis using infrared, visible light, ultraviolet using infrared
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B3/00—Devices comprising flexible or deformable elements, e.g. comprising elastic tongues or membranes
- B81B3/0018—Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
- B81B3/0021—Transducers for transforming electrical into mechanical energy or vice versa
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
- B81C1/00—Manufacture or treatment of devices or systems in or on a substrate
- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
- B81C1/00134—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems comprising flexible or deformable structures
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L11/00—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00
- G01L11/02—Measuring steady or quasi-steady pressure of a fluid or a fluent solid material by means not provided for in group G01L7/00 or G01L9/00 by optical means
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/16—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring several components of force
- G01L5/166—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes for measuring several components of force using photoelectric means
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B2201/00—Specific applications of microelectromechanical systems
- B81B2201/02—Sensors
- B81B2201/0264—Pressure sensors
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Abstract
Disclosed are a MEMS pressure sensor and a method for manufacturing the same, the MEMS pressure sensor comprising: a substrate; a thermopile structure located on the substrate; the bonding layer is positioned on the substrate and surrounds the thermopile structure; the transparent layer is positioned on the surface, far away from the substrate, of the bonding layer, a groove is formed in the surface, close to the substrate, of the transparent layer, and a lens structure is arranged in the groove; and a reflective layer on a surface of the transparent layer remote from the bonding layer, the reflective layer having a through hole therein extending through the reflective layer; the position of the through hole corresponds to that of the convex lens, and the through hole is used for receiving infrared light, so that the infrared light irradiates the transparent layer and further irradiates the thermopile structure through the lens structure.
Description
Technical Field
The invention relates to the technical field of semiconductors, in particular to an MEMS pressure sensor and a preparation method thereof.
Background
MEMS devices are micro-electromechanical devices that have been developed based on microelectronics and are fabricated using micro-fabrication 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 a parasitic problem in a measurement process, which affects measurement sensitivity.
Disclosure of Invention
In view of the foregoing problems, an object of the present invention is to provide a MEMS pressure sensor and a method for manufacturing the same, which uses a thermopile structure and a lens structure to replace the conventional piezoresistive MEMS pressure sensor and capacitive MEMS pressure sensor, thereby reducing parasitic capacitance and improving sensitivity.
A first aspect of the present invention provides a MEMS pressure sensor comprising:
a substrate;
a thermopile structure located on the substrate;
the bonding layer is positioned on the substrate and surrounds the thermopile structure;
the transparent layer is positioned on the surface, far away from the substrate, of the bonding layer, a groove is formed in the surface, close to the substrate, of the transparent layer, and a lens structure is arranged in the groove; and
a reflective layer on a surface of the transparent layer remote from the bonding layer, the reflective layer having a through hole therein extending through the reflective layer;
the position of the through hole corresponds to that of the convex lens, and the through hole is used for receiving infrared light, so that the infrared light irradiates the transparent layer and further 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, the dielectric layer is located on the substrate, and the thermopile structure is embedded in the dielectric layer.
In some embodiments, the dielectric layer includes a first dielectric layer and a second dielectric layer stacked, the first dielectric layer is located on the first surface of the substrate, and the second dielectric layer is located on the surface of the first dielectric layer.
In some embodiments, the contact metal is included, and the contact metal extends from the second surface of the substrate to the direction of the second dielectric layer, penetrates through the substrate and the first dielectric layer, and stops in the second dielectric layer.
In some embodiments, the thermopile structure includes a plurality of thermocouples and a plurality of metal connection lines connecting a plurality of mutually separated thermocouples in an end-to-end sequence such that the plurality of thermocouples are connected in series to form the thermopile structure.
In some embodiments, both ends of the thermocouples in series are connected to the respective contact metals via the metal connection lines.
In some embodiments, a pad is included on the second surface of the substrate, the pad being electrically connected to 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 hollow inside, 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, and the thermopile structure and the lens structure are located in the cavity.
The second aspect of the present invention provides a method for manufacturing a MEMS pressure sensor, comprising:
forming a thermopile structure on a substrate;
forming a first bonding layer on the surface of the substrate;
forming a reflective layer having a through hole on a second surface of the transparent layer;
forming a second bonding layer on the first surface of the transparent layer;
forming a groove and a lens structure positioned in the groove on the first surface of the transparent layer;
bonding the first bonding layer and the second bonding layer together to form the bonding layer;
the position of the through hole corresponds to that of the convex lens, and the through hole is used for receiving infrared light, so that the infrared light irradiates the transparent layer and further irradiates the thermopile structure through the lens structure.
In some embodiments, forming the thermopile structure further comprises forming a dielectric layer on the first surface of the substrate, wherein the thermopile structure is embedded in the dielectric layer.
In some embodiments, the method of forming the dielectric layer comprises:
forming a first dielectric layer on the substrate; and
and forming a first layer of second dielectric layer on the first dielectric layer.
In some embodiments, the method comprises: and forming a contact metal after the first layer of the second dielectric layer is formed.
In some embodiments, 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
and filling a metal material in the first contact hole to form contact metal.
In some embodiments, a method of forming the thermopile structure includes:
forming a plurality of thermocouples which are separated from each other on the surface of the first dielectric layer and the second dielectric layer;
forming a second dielectric layer with a second contact hole;
forming a plurality of metal connecting wires, wherein each metal connecting wire is positioned on the surface of the second layer of the second dielectric layer and fills the corresponding second contact hole; and
forming a third second dielectric layer, wherein the third second dielectric layer covers the metal connecting line;
the metal connecting wires connect a plurality of mutually separated thermocouples end to end in sequence, so that the plurality of thermocouples are connected in series to form a thermopile structure.
In some embodiments, both ends of the thermocouples in series are connected to the respective contact metals via the metal connection lines.
In some embodiments, pads are formed on the second surface of the substrate simultaneously with the formation of the first bonding layer, the pads being electrically connected to respective contact metals.
In some embodiments, the first dielectric layer is a silicon oxide layer, and the first layer of the second dielectric layer, the second layer of the second dielectric layer, and the third layer of the second dielectric layer are silicon nitride layers.
In some embodiments, the bonding layer is hollow inside, 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, and the thermopile structure and the lens structure are located in the cavity.
The MEMS pressure sensor provided by the invention integrates the following 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 high measurement precision and quick response time.
Furthermore, the core components of the embodiment of the invention only comprise the transparent layer, the reflecting layer, the lens structure, the infrared thermopile structure and the like, the structure is simple, the implementation is easy, and the wafer level packaging is adopted, so that the miniaturization of the volume of the sensor can be realized.
Furthermore, in the embodiment of the invention, the core component lens structure and the infrared thermopile structure of the MEMS pressure sensor are integrated in the sealed cavity, so that air leakage is not easy to occur, and the reliability is high.
Furthermore, in the embodiment of the invention, the MEMS pressure sensor is formed by growing silicon oxide, polysilicon, silicon nitride and metal processes, and the preparation process of the MEMS pressure sensor is compatible with the integrated circuit process, so that a feasible basis is provided for realizing the monolithic integration of the MEMS pressure sensor and the processing circuit, and meanwhile, the complexity of the process can be reduced, and the cost can be reduced.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:
FIG. 1 illustrates a cross-sectional view of a MEMS pressure sensor of an embodiment of the present invention;
FIG. 2 illustrates a schematic top view of a MEMS pressure sensor of an embodiment of the present invention that does not include a reflective layer and a transparent layer;
FIGS. 3 a-16 a are cross-sectional views illustrating various stages in the fabrication of a MEMS pressure sensor in accordance with an embodiment of the present invention;
fig. 3 b-16 b show top views of various stages in the fabrication of a MEMS pressure sensor in accordance with an embodiment of the present invention.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown.
The present invention 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 invention, and fig. 2 is a schematic top view of the MEMS pressure sensor according to an embodiment of the present invention, which does not include a reflective layer and a transparent layer, wherein a portion shown by a dotted line in fig. 2 is embedded in 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 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, 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 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 second dielectric layer 140 is, for example, a silicon nitride layer.
The plurality of thermopile structures 150 are embedded in the second dielectric layer 140. Each set of the thermopile structure 150 includes a plurality of thermocouples 151 and a plurality of metal connection lines 152, the metal connection lines 152 sequentially connecting the plurality of thermocouples 151, which are separated from each other, end to end such that the plurality of thermocouples are connected in series to form the thermopile structure 150. The thermocouple 151 is made of, for example, polysilicon, and the metal connection wire 152 is made of, for example, aluminum metal.
In a specific embodiment, the substrate 110, the first dielectric layer 120, and the second dielectric layer 140 are all rectangular, and the MEMS pressure sensor 10 includes 4 sets of thermopile structures 150, where each set of the thermopile structures 150 is 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 through 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 the 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 at the second surface of the substrate 110 are respectively connected to pads 130a.
The bonding layer 170 is positioned on the surface of the second medium layer 140, and the transparent layer 190 is positioned on the surface of the bonding layer 170 far away from the second medium 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 inside, an inner surface of the bonding layer 170 and an 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 disposed on the second surface of the transparent layer 190, the reflective layer 180 has a through hole 181 therein, the through hole 181 is disposed in a central region of the transparent layer 190 corresponding to the position of the lens structure 191, and the through hole 181 penetrates 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, a gold material layer. The transparent layer 190 is, for example, a glass layer. The transparent layer 190 is used to sense the external pressure.
The MEMS pressure sensor of the embodiment of the invention integrates core components: the transparent layer 190, the lens structure 191, the reflective layer 180 and the infrared thermopile structure 150 may be applied to conventional air pressure detection or more complex three-dimensional mechanical detection, and specifically, infrared light emitted from the infrared light source 20 located outside the MEMS pressure sensor irradiates a portion of the reflective layer 180, reflects off the MEMS pressure sensor via the reflective layer 180, irradiates a portion of the through hole 181, irradiates the transparent layer 190 via the through hole 181, further irradiates the lens structure 191 via the transparent layer 190, and refracts to the thermopile structure 150 via the lens structure 191; when the transparent layer 190 receives external force and deforms, the lens structure 191 follows the transparent layer 190 and deforms together, the optical path of infrared light received by the thermopile structure 150 changes, and then the pressure or three-dimensional vector mechanical parameters can be sensed by measuring the output voltage of the infrared thermopile structure 150.
Furthermore, the core components of the embodiment of the invention only comprise the transparent layer, the reflecting layer, the lens structure, the infrared thermopile structure and the like, the structure is simple, the implementation is easy, and the wafer level packaging is adopted, so that the miniaturization of the volume of the sensor can be realized.
Further, in the embodiment of the invention, the lens structure 191 as the core component of the MEMS pressure sensor and the infrared thermopile structure are integrated in the sealed cavity, so that air leakage is not easy to occur, and reliability is high.
Furthermore, in the embodiment of the invention, the preparation process of the MEMS pressure sensor is compatible with the integrated circuit process, so that a feasible basis is provided for realizing the monolithic integration of the MEMS pressure sensor and the processing circuit, and meanwhile, the process complexity and the cost can be reduced.
FIGS. 3 a-16 a are cross-sectional views illustrating various stages in the fabrication of a MEMS pressure sensor in accordance with an embodiment of the present invention; fig. 3b to 16b are top views illustrating various stages in the manufacturing process of the MEMS pressure sensor according to the embodiment of the invention, wherein fig. 3a to 15a are cross-sectional views along the AA direction of fig. 3b to 15 b. The following describes a process for manufacturing a MEMS pressure sensor according to an embodiment of the present invention 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 layer of a 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 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 second dielectric layer 141 is, for example, a silicon nitride layer.
As shown in fig. 4a and 4b, the first layer of the second dielectric layer 141, the first dielectric layer 120, and the substrate 110 are etched, and a first contact hole 110a is formed in the first layer of the second dielectric layer 141, the first dielectric layer 120, and the substrate 110.
In this step, for example, a photoresist layer is formed on the surface of the first second dielectric layer 141, the photoresist layer is patterned by using a photolithography process to form a photoresist mask, and the first 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 of the 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, a conductive material is filled inside the first contact hole 110a, for example, using a deposition process, and the conductive material outside the first contact hole 110a is polished using a polishing process, so that the conductive material is filled only inside the first contact hole 110a, thereby forming the contact metal 130. The contact metal 130 is exposed on a second surface of the substrate 110 (the first surface and the second surface of the substrate 110 are opposite) and a surface of the first layer of the second dielectric layer 141.
As shown in fig. 6a and 6b, a thermocouple 151 is formed on the surface of the first and second dielectric layers 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 by, for example, a deposition process, and then the polysilicon layer is patterned by, for example, a photolithography process and an etching process, so as to form the thermocouple 151. The thermocouple device comprises a plurality of thermocouples 151, wherein the thermocouples 151 are separated from each other, and each thermocouple 151 is not in contact with the contact metal 130 exposed on the surface of the first layer of the second dielectric layer 141.
As shown in fig. 7a and 7b, a second layer of the second dielectric layer 142 having a second contact hole 142a is formed.
In this step, for example, a deposition process is used to form a second dielectric layer 142 on the surface of the first dielectric layer 141, and the second dielectric layer 142 covers the surface of the first dielectric layer 141, the surface of the contact metal 131, and the surface and the sidewall of the thermocouple 151. Next, the second layer of 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 layer of 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 surfaces of the thermocouples 151. Wherein the second contact holes 142a are respectively located at the head and 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 by, for example, 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 by, for example, a photolithography process and an etching process, so as to form metal connection lines 152,1, each of the metal connection lines 152 connects one end of one thermocouple 151 with one end of another thermocouple 151, so that the metal connection line 152 connects a plurality of thermocouples 151 separated from each other in series, and connects two ends of the thermocouples 151 connected in series to corresponding contact metals 130, respectively, and the metal connection line 152 and the thermocouples 151 constitute a thermopile structure 150.
In this embodiment, the substrate 110 is rectangular, and the four thermopile structures 150 are respectively arranged on four sides of the substrate 110.
As shown in fig. 9a and 9b, a third layer of 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 layer of second dielectric layer 143 is, for example, a silicon nitride layer. The first, second, and third dielectric layers 141, 142, 143 form 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 layer of the second dielectric layer 143 and a pad 130a is formed on the surface of the substrate 110 away from the dielectric layer 120.
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, for example, by a deposition process, and then the metal material layer is patterned by, for example, a photolithography and etching process, so as to form a first bonding layer 171 on the surface of the first dielectric layer 124, and form a plurality of pads 130a separated from each other on the surface of the substrate 110 away from the dielectric layer 20, where the first bonding layer 171 is located at the 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 in contact with the contact metal 130 exposed on the surface of the substrate 110. In this embodiment, the material of the pad 130a and the first bonding layer 171 is, for example, 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, for example, a deposition process is used to form the reflective layer 180 on the second surface of the transparent layer 190, and then a photolithography and etching process is used to form the through hole 181 in the reflective layer 180, where the through hole 181 is located in the central region 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 made of a glass layer, and the reflective layer 180 is made of a gold material 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, for example, a sputtering process is used to form a metal material layer on the first surface of the transparent layer 190, and then, for example, an electroplating process is used to thicken the metal material layer, and a photolithography process and an etching process are used to etch the metal material layer, so as to form the second bonding layer 172. The second bonding layer 172 is located at the 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 brought together. Wherein the first bonding layer 171 and the second bonding layer 172 together form a bonding layer 170, and an inner surface of the bonding layer 170 and an inner surface of the recess of the transparent layer 190 define a sealed 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.
As shown in fig. 16a and 16b, a 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 by 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.
The MEMS pressure sensor provided by the invention integrates the following 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 high measurement precision and quick response time.
Furthermore, the core components of the embodiment of the invention only comprise the transparent layer, the reflecting layer, the lens structure, the infrared thermopile structure and the like, the structure is simple, the implementation is easy, and the wafer level packaging is adopted, so that the miniaturization of the sensor volume can be realized.
Furthermore, in the embodiment of the invention, the lens structure of the core component of the MEMS pressure sensor and the infrared thermopile structure are integrated in the sealed cavity, so that air leakage is not easy to occur, and the reliability is high.
Furthermore, in the embodiment of the invention, the MEMS pressure sensor is formed by growing silicon oxide, polysilicon, silicon nitride and metal processes, and the preparation process is compatible with the integrated circuit process, so that a feasible basis is provided for realizing the monolithic integration of the MEMS pressure sensor and the processing circuit, and meanwhile, the complexity of the process can be reduced, and the cost can be reduced.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. 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 invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.
Claims (20)
1. A MEMS pressure sensor, comprising:
a substrate;
a thermopile structure located on the substrate;
the bonding layer is positioned on the substrate and surrounds the thermopile structure;
the transparent layer is positioned on the surface, far away from the substrate, of the bonding layer, a groove is formed in the surface, close to the substrate, of the transparent layer, and a lens structure is arranged in the groove; and
a reflective layer on a surface of the transparent layer remote from the bonding layer, the reflective layer having a through hole therethrough;
the position of the through hole corresponds to that of the convex lens, and the through hole is used for receiving infrared light, so that the infrared light irradiates the transparent layer and further irradiates the thermopile structure through the lens structure.
2. The MEMS pressure sensor of claim 1, wherein the substrate has a back cavity that extends 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 1, wherein the dielectric layer comprises a first dielectric layer and a second dielectric layer that are stacked, the first dielectric layer being located on the 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 in a direction towards 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 includes a plurality of thermocouples and a plurality of metal connecting wires connecting the plurality of mutually separated thermocouples in end-to-end sequence such that the plurality of thermocouples are connected in series forming 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 lines.
8. The MEMS pressure sensor of claim 5, comprising pads at the second surface of the substrate, the pads being electrically connected with 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 hollow inside, 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.
11. A method of making a MEMS pressure sensor, comprising:
forming a thermopile structure on a substrate;
forming a first bonding layer on the surface of the substrate;
forming a reflective layer having a through hole on a second surface of the transparent layer;
forming a second bonding layer on the first surface of the transparent layer;
forming a groove and a lens structure positioned in the groove on the first surface of the transparent layer;
bonding the first bonding layer and the second bonding layer together to form the bonding layer;
the position of the through hole corresponds to that of the convex lens, and the through hole is used for receiving infrared light, so that the infrared light irradiates the transparent layer and further irradiates the thermopile structure through the lens structure.
12. The method of claim 11, wherein forming the thermopile structure further comprises forming a dielectric layer on the first surface of the substrate, the thermopile structure being embedded within the dielectric layer.
13. The method of claim 12, wherein forming the dielectric layer comprises:
forming a first dielectric layer on the substrate; and
and forming a first layer of second dielectric layer on the first dielectric layer.
14. The method of claim 13, comprising: and forming a contact metal after the first layer of the second dielectric layer is formed.
15. The method of claim 14, wherein 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
and filling a metal material in the first contact hole to form contact metal.
16. The method of claim 14, wherein forming the thermopile structure comprises:
forming a plurality of thermocouples which are separated from each other on the surface of the first layer of the second medium layer;
forming a second dielectric layer with a second contact hole;
forming a plurality of metal connecting lines, wherein each metal connecting line is positioned on the surface of the second dielectric layer and fills the corresponding second contact hole; and
forming a third layer of second dielectric layer, wherein the third layer of second dielectric layer covers the metal connecting line;
the metal connecting wires connect a plurality of mutually separated thermocouples end to end in sequence, so that the plurality of thermocouples are connected in series to form a thermopile structure.
17. The method of claim 16, wherein both ends of the thermocouples in series are connected to respective contact metals via the metal connection wires.
18. The method of claim 11, wherein a pad is formed on the second surface of the substrate concurrently with forming the first bonding layer, the pad being electrically connected to a corresponding contact metal.
19. The method of claim 16, wherein the first dielectric layer is a silicon oxide layer, and the first, second, and third second dielectric layers are silicon nitride layers.
20. The method of claim 1, wherein the bonding layer is hollow inside, 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.
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| CN202211138067.2A CN115420408A (en) | 2022-09-19 | 2022-09-19 | MEMS pressure sensor and preparation method thereof |
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