CN115507980A - MEMS pressure sensor and preparation method thereof - Google Patents
MEMS pressure sensor and preparation method thereof Download PDFInfo
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- CN115507980A CN115507980A CN202211138074.2A CN202211138074A CN115507980A CN 115507980 A CN115507980 A CN 115507980A CN 202211138074 A CN202211138074 A CN 202211138074A CN 115507980 A CN115507980 A CN 115507980A
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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
- G01L1/18—Measuring force or stress, in general using properties of piezo-resistive materials, i.e. materials of which the ohmic resistance varies according to changes in magnitude or direction of force applied to the material
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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
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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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- B81C—PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS
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- B81C1/00015—Manufacture or treatment of devices or systems in or on a substrate for manufacturing microsystems
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- B81—MICROSTRUCTURAL TECHNOLOGY
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- 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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- 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; an infrared light source located on the substrate; the thermopile structure is positioned on the substrate and is mutually separated from the infrared light source; the bonding layer is positioned on the dielectric layer and surrounds the infrared light source and the thermopile structure; the reflecting layer is positioned on the surface of the bonding layer, which is far away from the dielectric layer; the pressure sensing layer is positioned on the surface of the reflecting layer, which is far away from the bonding layer, and is used for sensing pressure and driving the reflecting layer to deform under the action of stress; the inner surface of the bonding layer and the surface of the reflecting layer opposite to the dielectric layer form a reflecting surface, and infrared light emitted by the infrared light source is reflected to the thermopile structure through the reflecting layer.
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 sensors are usually piezoresistive MEMS pressure sensors and capacitive MEMS pressure sensors, which usually have parasitic problems in the measurement process and affect the 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 an infrared light source 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;
an infrared light source located on the substrate;
the thermopile structure is positioned on the substrate and is mutually separated from the infrared light source;
the bonding layer is positioned on the dielectric layer and surrounds the infrared light source and the thermopile structure; the reflecting layer is positioned on the surface of the bonding layer, which is far away from the dielectric layer; and
the pressure sensing layer is positioned on the surface of the reflecting layer, which is far away from the bonding layer, and is used for sensing pressure and driving the reflecting layer to deform when stressed;
the inner surface of the bonding layer and the surface of the reflecting layer opposite to the dielectric layer form a reflecting surface, and infrared light emitted by the infrared light source is reflected to the thermopile structure through the reflecting layer.
In some embodiments, the infrared light source further includes a dielectric layer, the dielectric layer is located on the first surface of the substrate, the thermopile structure is embedded inside the dielectric layer, and the infrared light source is located inside the dielectric layer and exposed on the surface of the dielectric layer far from the substrate.
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 first metal connection lines sequentially connecting the plurality of thermocouples separated from each other end to end 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 first metal connection line.
In some embodiments, the infrared light source is connected to the respective contact metal via a second metal connection line.
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 thermopile structure includes multiple groups surrounding the infrared light source.
In some embodiments, the substrate has a back cavity that extends through the substrate.
The second aspect of the present invention provides a method for manufacturing a MEMS pressure sensor, including:
forming a thermopile structure and an infrared light source on a substrate, wherein the thermopile structure and the infrared light source are separated from each other;
forming a first bonding layer on the substrate, the first bonding layer surrounding the infrared light source and the thermopile structure; (ii) a
Forming a reflecting layer and a second bonding layer on the pressure sensing layer in sequence;
bonding the first bonding layer and the second bonding layer together to form the bonding layer;
the inner surface of the bonding layer and the surface of the reflecting layer opposite to the dielectric layer form a reflecting surface, infrared light emitted by the infrared light source is reflected to the thermopile structure through the reflecting layer, and the pressure sensing layer is used for sensing pressure and driving the reflecting layer to deform when stressed.
In some embodiments, forming a gap between the thermopile structure and the infrared light source further includes forming a dielectric layer on the first surface of the substrate, the thermopile structure being embedded inside the dielectric layer, and the infrared light source being located inside the dielectric layer and exposed to a surface of the dielectric layer away from the substrate.
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 layer of the second medium layer;
forming a second dielectric layer with a second contact hole;
forming a plurality of first metal connecting lines, wherein each first 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 first metal connecting line;
the first metal connecting line connects a plurality of thermocouples separated from each other 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 first metal connection line.
In some embodiments, the first metal connection line is formed simultaneously with a second metal connection line, and the infrared light source is connected to the corresponding contact metal via the second metal connection line.
In some embodiments, a method of forming the infrared light source comprises:
forming a groove on the third layer of the second dielectric layer, wherein the groove extends from the surface of the third layer of the second dielectric layer to the inside of the third layer of the second dielectric layer;
and filling infrared black body materials in the grooves to form the infrared light source.
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 thermopile structure includes multiple groups surrounding the infrared light source.
In some embodiments, further comprising a back cavity on the substrate, the back cavity extending through the substrate.
The MEMS pressure sensor provided by the invention integrates the following core components: the pressure sensing layer, the reflecting layer, the infrared light source 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 pressure sensing layer, the reflecting layer, the infrared light source, the infrared thermopile structure and the like, the structure is simple, the implementation is easy, and the miniaturization of the sensor volume can be realized by adopting wafer level packaging.
Furthermore, in the embodiment of the invention, the infrared light source is integrated in the device, and an external auxiliary light source is not needed.
Furthermore, in the embodiment of the invention, the infrared light source and the infrared thermopile structure which are core components 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 pressure sensing 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 drawn to scale. In addition, certain well known components 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 the embodiment of the present invention, which does not include a reflective layer and a pressure-sensitive 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, an infrared light source 160, a contact metal 130, a bonding layer 170, a reflective layer 180, and a pressure sensing 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 first metal connection lines 152, and the first metal connection lines 152 sequentially connect 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 material of the thermocouple 151 is, for example, polysilicon, and the material of the first metal connection line 152 is, for example, metal aluminum.
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 inside the second dielectric layer 140, that is, the infrared light source 160 is exposed to the surface of the second dielectric layer 140 away from the substrate 110. The infrared light source 160 is made of an infrared black body material (such as tungsten, nickel chromium, etc.).
Further, the groups of thermopile 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 rectangular, and the infrared light source 160 is located in a central region of the second dielectric layer 140; the MEMS pressure sensor 10 includes 4 sets of thermopile structures 150, each set of the 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 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 between the thermopile structure 150 and the infrared light source 160 and the outside.
Specifically, the contact metal 130 includes a first contact metal 131 and a second contact metal 132 separated from each other. Both ends of the thermocouple 151 of each group of the thermopile structures 150 are connected to the first contact metal 131 via a first metal connection line 152, and are electrically connected to the outside via the first contact metal 131. The infrared light source 160 is electrically connected to the second contact metal 132 through a second metal connection line 161, and is electrically connected to the outside through the second contact metal 132.
Further, the contact metals 130 exposed on the second surface of the substrate 110 are respectively connected to the pads 130a.
The bonding layer 170 is located on the surface of the second dielectric layer 140, and the reflective layer 180 is located on the surface of the bonding layer 170 away from the second dielectric layer 140. The bonding layer 170 is hollow, 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 cavity 102, and the cavity 102 provides a propagation space for infrared light emitted by the infrared light 160.
Further, the bonding layer 170 and the reflective layer 180 are made of the same material, for example, both of gold material layers, an inner surface of the bonding layer 170 and a surface of the reflective layer 180 opposite to the second dielectric layer 140 serve as a reflective surface of the infrared light source 160, and light emitted by the infrared light source 160 is reflected to the thermopile structure 150 via the reflective surface.
The pressure sensing layer 190 is located on a surface of the reflective layer 180 away from the bonding layer, and is used for sensing external pressure.
The MEMS pressure sensor of the embodiment of the invention integrates core components: the pressure sensing layer 190, the reflective layer 180, the infrared light source 160 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 160 is irradiated to the reflective layer 180, and is reflected to the infrared thermopile structure 150 via the reflective layer 180; when the forced induction layer 190 receives external force and takes place the deformation, the reflection stratum 180 follows forced induction layer 190 takes place deformation together, the optical path of the infrared light that thermopile structure 150 received changes, and then can carry out perception atmospheric pressure or three-dimensional vector mechanics parameter through the size of measuring infrared thermopile structure 150's output voltage, compares in traditional piezoresistive pressure sensor or capacitanc pressure sensor, and the pressure sensor of this application has higher measurement accuracy, and response time is very fast.
Furthermore, the core components of the embodiment of the invention only comprise the pressure sensing layer, the reflecting layer, the infrared light source, the infrared thermopile structure and the like, the structure is simple, the implementation is easy, and the miniaturization of the sensor volume can be realized by adopting wafer level packaging.
Furthermore, in the embodiment of the invention, the infrared light source is integrated in the device, and an external auxiliary light source is not needed.
Furthermore, in the embodiment of the invention, the infrared light source and the infrared thermopile structure which are core components 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 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, a second 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, and first dielectric layers 141 are, for example, silicon nitride layers.
As shown in fig. 4a and 4b, the first layer of the second first 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 first 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, second, first and second dielectric layers 141, 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 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. Wherein the contact metal 130 includes a first contact metal 131 and a second contact metal 132 separated from each other.
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 structure comprises a plurality of thermocouples 151, wherein the plurality of thermocouples 151 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 dielectric layer 141.
As shown in fig. 7a and 7b, a second layer of the second dielectric layer 142 having the 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 to expose the surface of the contact metal 130 and a portion of the surfaces of the thermocouples 151. In this embodiment, the second dielectric layer 142 is, for example, a silicon nitride layer.
As shown in fig. 8a and 8b, a first metal connection line 152 and a second metal connection line 161 are formed.
In this step, for example, a deposition process is used to form a conductive metal material on the surface of the second dielectric layer 142, wherein the conductive metal material covers the surface of the second dielectric layer 142 and fills the second contact hole 142a, and then, for example, a photolithography process and an etching process are used to pattern the conductive metal layer, so as to form the first metal connection line 152 and the second metal connection line 161.
The first metal connection line 152 connects a plurality of thermocouples 151, which are separated from each other, in series, and both ends of the thermocouples 151 connected in series are respectively connected to the corresponding first contact metals 131, and the first metal connection line 152 and the thermocouples 151 constitute a thermopile structure 150. In this embodiment, the substrate 110 is rectangular, and the four groups of thermopile structures 150 are respectively arranged at four sides of the substrate 110, surrounding the subsequently formed light source. The second metal connection line 161 is used to connect a subsequently formed light source to the second contact metal 132.
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, the first metal connection line 152 and the second metal connection line 161. 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, an infrared light source 160 is formed in the third layer of second dielectric layer 143.
In this step, a groove is formed in the third layer of second dielectric layer 143, and the groove extends from the surface of the third layer of second dielectric layer 143 toward the substrate 110. The recess is then filled with an infrared black body material (e.g., tungsten, nickel chromium, etc.), and the infrared black body material is patterned to form an infrared light source 160 located in the recess. The infrared light source 160 is in contact with the second metal connecting line 161, and is connected to the second contact metal 132 through the second metal connecting line 161.
As shown in fig. 11a and 11b, 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. 12a, 12b, 13a and 13b, a pressure-sensitive layer 190 is provided, and a reflective layer 180 is formed on a first surface of the pressure-sensitive layer 190. In this step, the reflective layer 180 is formed on the surface of the pressure-sensitive layer 190 by, for example, a deposition process, wherein the reflective layer 180 is, for example, a gold material layer.
As shown in fig. 14a and 14b, a second bonding layer 172 is formed on a surface of the reflective layer 180.
In this step, a thick photoresist layer is formed on the surface of the reflective layer 180, and a mask layer is formed by performing photolithography on the rear photoresist layer, wherein the mask layer is located in the central region of the reflective layer 180, and the peripheral edge of the surface of the reflective layer 180 is exposed. Next, a second bonding layer 172 is formed on the edge of the reflective layer 180, for example, by using an electroplating process. And removing the mask layer by a stripping process after the second bonding layer 172 is formed. The second bonding layer 172 is located at the edge of the reflective layer, corresponding to the position of the first bonding layer 171.
As shown in fig. 15a and 15b, the first bonding layer and the second bonding layer are brought together. Wherein the first bonding layer 171 and the second bonding layer 172 form a bonding layer 170, and an inner surface of the bonding layer 170 and a surface of the reflective layer 180 opposite to the second dielectric layer 140 define a sealed cavity 102, and the cavity 102 provides a transmission space for infrared light emitted from the infrared light source 160.
As shown in fig. 16a and 16b, a back cavity 101 is formed.
In this step, a resist layer is formed on the first 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 MEMS pressure sensor provided by the invention integrates the following core components: the pressure sensing layer, the reflecting layer, the infrared light source 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 pressure sensing layer, the reflecting layer, the infrared light source, the infrared thermopile structure and the like, the structure is simple, the implementation is easy, and the miniaturization of the sensor volume can be realized by adopting wafer level packaging.
Furthermore, in the embodiment of the invention, the infrared light source is integrated in the device, and an external auxiliary light source is not needed.
Furthermore, in the embodiment of the invention, the infrared light source and the infrared thermopile structure which are core components 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 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 (24)
1. A MEMS pressure sensor, comprising:
a substrate;
an infrared light source located on the substrate;
the thermopile structure is positioned on the substrate and is mutually separated from the infrared light source;
the bonding layer is positioned on the dielectric layer and surrounds the infrared light source and the thermopile structure;
the reflecting layer is positioned on the surface of the bonding layer, which is far away from the dielectric layer; and
the pressure sensing layer is positioned on the surface of the reflecting layer, which is far away from the bonding layer, and is used for sensing pressure and driving the reflecting layer to deform when stressed;
the inner surface of the bonding layer and the surface of the reflecting layer opposite to the dielectric layer form a reflecting surface, and infrared light emitted by the infrared light source is reflected to the thermopile structure through the reflecting layer.
2. The MEMS pressure sensor of claim 1, further comprising a dielectric layer, the dielectric layer being located on the first surface of the substrate, the thermopile structure being embedded within the dielectric layer, the infrared light source being located within the dielectric layer and being exposed to a surface of the dielectric layer remote from the substrate.
3. The MEMS pressure sensor of claim 2, 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.
4. The MEMS pressure sensor of claim 3, comprising a contact metal extending from the second surface of the substrate in a direction toward the second dielectric layer, through the substrate and the first dielectric layer, and terminating within the second dielectric layer.
5. The MEMS pressure sensor of claim 4, wherein the thermopile structure includes a plurality of thermocouples and a plurality of first metal connection lines connecting the plurality of mutually separated thermocouples in end-to-end sequence such that the plurality of thermocouples are connected in series to form the thermopile structure.
6. The MEMS pressure sensor of claim 5, wherein both ends of the series of thermocouples are connected to respective contact metals via the first metal connection lines.
7. The MEMS pressure sensor of claim 4, wherein the infrared light source is connected to the respective contact metal via a second metal connection line.
8. The MEMS pressure sensor of claim 4, comprising pads on the second surface of the substrate, the pads being electrically connected to respective contact metals.
9. The MEMS pressure sensor of claim 3, 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 1, wherein the thermopile structure comprises multiple groups, the multiple groups surrounding the infrared light source.
11. The MEMS pressure sensor of claim 1, wherein the substrate has a back cavity that extends through the substrate.
12. A method of making a MEMS pressure sensor, comprising:
forming a thermopile structure and an infrared light source on a substrate, wherein the thermopile structure and the infrared light source are separated from each other;
forming a first bonding layer on the substrate, the first bonding layer surrounding the infrared light source and the thermopile structure; (ii) a
Forming a reflecting layer and a second bonding layer on the pressure sensing layer in sequence;
bonding the first bonding layer and the second bonding layer together to form the bonding layer;
the inner surface of the bonding layer and the surface of the reflecting layer opposite to the dielectric layer form a reflecting surface, infrared light emitted by the infrared light source is reflected to the thermopile structure through the reflecting layer, and the pressure sensing layer is used for sensing pressure and driving the reflecting layer to deform when stressed.
13. The method of claim 12, wherein forming a gap between the thermopile structure and the infrared light source further comprises forming a dielectric layer on the first surface of the substrate, the thermopile structure being embedded within the dielectric layer, and the infrared light source being within the dielectric layer and exposed to a surface of the dielectric layer remote from the substrate.
14. The method of claim 13, 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.
15. The method of claim 14, comprising: and forming a contact metal after the first layer of the second dielectric layer is formed.
16. The method of claim 15, 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.
17. The method of claim 15, wherein forming the thermopile structure comprises:
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 first metal connecting lines, wherein each first 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 first metal connecting line;
the first metal connecting wire connects 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.
18. The method of claim 17, wherein both ends of the thermocouples in series are connected to respective contact metals via the first metal connection line.
19. The method of claim 17, wherein the first metal connection line is formed simultaneously with forming a second metal connection line, the infrared light source being connected to the respective contact metal via the second metal connection line.
20. The method of claim 17, wherein forming the infrared light source comprises:
forming a groove on the third layer of second dielectric layer, wherein the groove extends from the surface of the third layer of second dielectric layer to the inside of the third layer of second dielectric layer;
and filling infrared black body materials in the grooves to form the infrared light source.
21. The method of claim 12, wherein pads are formed on the second surface of the substrate concurrently with the forming of the first bonding layer, the pads being electrically connected to respective contact metals.
22. The method of claim 17, wherein the first dielectric layer is a silicon oxide layer, and the first, second, and third second dielectric layers are silicon nitride layers.
23. The method of claim 12, wherein the thermopile structure comprises a plurality of sets surrounding the infrared light source.
24. The method of claim 12, further comprising providing a back cavity in the substrate, the back cavity extending through the substrate.
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| CN202211138074.2A CN115507980A (en) | 2022-09-19 | 2022-09-19 | MEMS pressure sensor and preparation method thereof |
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| CN202211138074.2A CN115507980A (en) | 2022-09-19 | 2022-09-19 | MEMS pressure sensor and preparation method thereof |
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