Pressure and thermal multiplexing sensor and preparation method thereof

Abstract

The invention provides a pressure and thermal multiplexing sensor and a preparation method thereof. The pressure and thermal multiplexing sensor is provided with a thermopile with a suspended structure and can measure pressure and temperature at the same time. Further, the pressure and thermal multiplexing sensor is of a bridge type structure and sequentially comprises a substrate, a supporting layer, a thermopile, an infrared absorption layer and a rigid packaging layer from bottom to top, the thermopile is of a multi-stage series structure, a thermal junction region of the thermopile is located in a central region of a micro-bridge suspension structure, and a cold junction region of the thermopile is located on the supporting layer on the top of the substrate. The central area of the micro-bridge suspension structure is corroded from the back surface through isotropic dry etching to form a cavity structure, the infrared absorption layer covers the central area of the micro-bridge suspension structure, and the rigid packaging layer covers the upper surface of the sensor. The pressure and temperature sensor can measure pressure and temperature at the same time, is manufactured by adopting a standard CMOS process general material and a manufacturing method, meets the requirements of integration and miniaturization in the field of intelligent sensing, and is expected to be widely applied.

Description

Technical Field

[0001] The present invention belongs to the technical field of pressure detection, and more specifically relates to a pressure and heat multiplexing sensor and a preparation method thereof. Background Art

[0002] A pressure sensor is a device or apparatus that can sense pressure signals and convert them into usable output electrical signals according to certain rules. A pressure sensor is usually composed of a pressure sensitive element and a signal processing unit. According to different test pressure types, pressure sensors can be divided into gauge pressure sensors, differential pressure sensors, and absolute pressure sensors. Pressure sensors are the most commonly used sensors in industrial practice. They are widely used in various industrial automatic control environments, involving many industries such as water conservancy and hydropower, railway transportation, intelligent buildings, production automatic control, aerospace, military industry, petrochemicals, oil wells, electricity, ships, machine tools, pipelines, etc.

[0003] Silicon-based pressure sensors are the mainstream of pressure sensors. They are based on polycrystalline silicon / single crystal silicon / silicon carbide, etc., and use microsystem manufacturing processes to prepare empty cup structures. They are made into sensitive elements along specific crystal directions on single crystal silicon wafers through doping. Subsequently, based on the Wheatstone bridge, the change in resistance is converted into an electrical signal for output, thus realizing the measurement of external pressure. Silicon-based pressure sensing technology cannot be used for thermal sensing. In silicon-based pressure sensing technology, temperature drift is suppressed by bridges, temperature compensation is compensated by measuring temperature through auxiliary equipment, and algorithms are used to compensate, which inevitably reduces the integration of devices.

[0004] The existing technology uses thermocouples as radiation heat sensors. Its device structure is similar to that of silicon piezoresistive sensors. It uses a heat-resistance layer to control the direction of heat transfer. The working element uses a heat-absorbing element to convert light into heat and a thermocouple to convert heat into electricity. It is more complicated than piezoresistive silicon sensors. This existing technology solution is relatively complex and difficult, and has high equipment requirements. It has multiple challenges, and its overall controllability is greatly reduced. It cannot be used for pressure sensing.

[0005] Based on the needs of industrial practice, it is necessary to provide a pressure and heat multiplexing sensor technology. Summary of the invention

[0006] Based on the technical problems existing in the prior art, the present invention provides a pressure and thermal multiplexed sensor and a preparation method thereof, aiming to solve the problems that the prior art silicon-based pressure sensors cannot be used for thermal sensing, and the technology is relatively complex, difficult, and has high equipment requirements. The sensor has the advantages of relatively simple structure, ability to measure temperature and pressure simultaneously, stronger functions, easy manufacture, and good controllability.

[0007] To achieve the above objective, according to a first aspect of the technical solution of the present invention, a pressure and heat multiplexing sensor is provided, which has a thermopile with a suspended structure and can measure pressure and temperature simultaneously.

[0008] Furthermore, the pressure and thermal multiplexing sensor adopts a bridge structure, which includes, from bottom to top, a substrate, a support layer, a thermopile, an infrared absorption layer and a rigid packaging layer; the bridge structure adopts a microbridge suspension structure, and the thermopile adopts a multi-stage series structure. The hot junction area of ​​the thermopile is located in the central area of ​​the microbridge suspension structure, and the cold junction area of ​​the thermopile is located on the top support layer of the substrate.

[0009] Preferably, the central area of ​​the microbridge suspension structure is etched from the back side by isotropic dry etching to form a cavity structure.

[0010] Furthermore, the infrared absorption layer covers the central area of ​​the microbridge suspension structure. The rigid packaging layer covers the entire upper surface of the sensor. The thermopile is a thermocouple or a thermocouple annular array.

[0011] More preferably, the substrate is any single crystal silicon substrate or silicon oxide substrate. The support layer is a silicon nitride film grown by plasma enhanced chemical vapor deposition, or a silicon oxide and silicon nitride film. The rigid packaging layer uses an aluminum oxide ceramic packaging layer with high transmittance.

[0012] According to a second aspect of the technical solution of the present invention, a method for preparing the above-mentioned pressure and thermal multiplexing sensor is provided, which comprises the following steps: Step S1, selecting a device to process a substrate and preparing a support layer; Step S2, using micro-nano processing technology to prepare a thermocouple, an infrared absorption layer and a rigid packaging layer; the micro-nano processing means include but are not limited to photolithography, FIB etching, electron beam etching, etc., to process the substrate into a hollow cup structure; Step S3, preparing the suspension structure using micro-nano processing technology; Step S4, multiple sensing element connection modes are used for different measurement purposes. Pure pressure measurement adopts Wheatstone bridge connection, and temperature / heat measurement adopts sensing element series connection.

[0013] Compared with the prior art, the method and system for preparing the pressure and heat multiplexing sensor of the present invention have the following beneficial effects: (1) The pressure and heat multiplexing sensor proposed in the present invention has a relatively simple structure, can measure temperature and pressure simultaneously, has stronger functions, is easy to manufacture, and has good controllability; (2) The pressure and heat multiplexing sensor produced by the present invention has a simple structure and is easy to process. It has low requirements on materials and equipment and can be produced on a large scale quickly, efficiently and at low cost.

[0014] (3) The pressure and heat multiplexed sensor prepared by the present invention can measure pressure and temperature simultaneously, which greatly facilitates industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0016] Figure 1 is a top view of a schematic diagram of a pressure and heat multiplexing sensor according to the present invention; Figure 2 is a side view of a schematic diagram of a pressure and thermal multiplexing sensor according to the present invention; Figure 3 A schematic diagram of a serial connection method of sensor elements according to the present invention; Figure 4 FIG. 4 is a bridge connection diagram of a sensor element according to the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] It should be noted that when an element is referred to as being "fixed to" or "arranged on" another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or indirectly connected to the other element. In the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0019] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0020] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0021] The present invention provides a pressure and heat multiplexing sensor and a preparation method thereof, wherein the pressure and heat multiplexing sensor has a thermopile with a suspended structure and can measure pressure and temperature simultaneously. Furthermore, the pressure and heat multiplexing sensor adopts a bridge structure, which comprises a substrate, a supporting layer, a thermopile, an infrared absorption layer and a rigid packaging layer from bottom to top; the bridge structure adopts a microbridge suspension structure, and the thermopile adopts a multi-stage series structure, the thermopile hot junction area is located in the central area of ​​the microbridge suspension structure, and the cold junction area is located on the top supporting layer of the substrate. The central area of ​​the microbridge suspension structure is corroded from the back by isotropic dry etching to form a cavity structure, the infrared absorption layer covers the central area of ​​the microbridge suspension structure, and the rigid packaging layer covers the entire upper surface of the sensor. The present invention can measure pressure and temperature simultaneously, and is manufactured using standard CMOS process general materials and manufacturing methods, meeting the integration and miniaturization requirements in the field of intelligent sensing, and is expected to be widely used.

[0022] The microbridge suspension structure of the present invention is a combination of a microbridge structure and a suspension structure. The microbridge structure of the present invention is a structural design at a micro-nano scale. The microbridge structure is made of a thin film material (such as metal, polymer, etc.) and has a bridge shape spanning two or more support points. It is characterized by small size, fine structure, and certain elasticity and flexibility. The microbridge structure of the present invention can be used as a sensor for measuring physical quantities such as pressure, strain, displacement, etc. When subjected to external force or pressure, the microbridge structure will deform, and the required physical quantity information can be obtained by measuring the deformation. At the same time, the microbridge structure of the present invention can be used as a microheater, which can be thermally expanded by powering on, and used for controlling microfluids, temperature control, and other applications. Furthermore, the suspension structure of the present invention adopts an elastic cantilever structure, which provides an operating space for microscale mechanical operations such as sensing, suspension, and manipulation. The present invention creatively combines the microbridge structure with the suspension structure, thereby realizing pressure and heat multiplexing sensing and detection.

[0023] In order to illustrate the technical solution of the present invention, the following is a description with reference to specific drawings and embodiments.

[0024] like Figure 1-Figure 2As shown, the present invention provides a pressure and heat multiplexing sensor, which adopts a microbridge structure. The entire pressure and heat multiplexing sensor includes five parts: a substrate, a support layer, a thermopile, an infrared absorption layer, and a rigid packaging layer. In a preferred embodiment, the thermopile is a thermocouple or a thermocouple annular array, the infrared absorption layer serves as a heat absorption layer, and the rigid packaging layer serves as a protective layer. The thermocouple annular array is a pair of thermocouples arranged around a central axis. Preferably, the thermocouple pairs in the thermocouple annular array are evenly and symmetrically arranged. The bridge structure adopts a microbridge suspension structure.

[0025] In one embodiment, a suspension structure is prepared on the back of the substrate by a dry etching process. The preferred suspension structure is the center of a microbridge suspension structure, and the support layer carries a thermocouple and an infrared absorption layer. The thermopile adopts a multi-stage series structure, the hot junction area of ​​the thermopile is located in the central area of ​​the microbridge suspension structure, and the cold junction area of ​​the thermopile is located on the top support layer of the substrate. The infrared absorption layer covers the central area of ​​the microbridge suspension structure to absorb radiant heat. The rigid packaging layer is located on the upper surface of the detector, which serves the purpose of protecting the infrared absorption layer and improving the mechanical strength of the sensor. The structural advantage of the pressure and heat multiplexing sensor of the present invention lies in the use of a suspension structure, an infrared absorption layer and a rigid packaging layer, which enables the detector to have excellent infrared light absorption capacity and good mechanical properties, so that the detector can measure temperature and pressure at the same time.

[0026] Furthermore, the substrate is any single crystal silicon substrate or silicon oxide substrate, and the supporting layer is a silicon nitride film grown by plasma enhanced chemical vapor deposition, or a silicon oxide and silicon nitride film. The thermocouple is made of materials such as bismuth telluride and antimony telluride or copper-constantan. The rigid packaging layer uses an aluminum oxide ceramic packaging layer with high transmittance. The materials of each layer of the detector include but are not limited to the above materials.

[0027] The mechanical and thermal composite sensor proposed in the present invention adopts general materials and manufacturing technology compatible with CMOS. The single-sided suspended structure is prepared by a back-side silicon dry etching process. Back-side etching does not require a top protective layer, which not only simplifies the detector preparation process and reduces the manufacturing cost, but also avoids surface contamination and etching damage. Furthermore, the present invention provides a method for preparing a pressure and thermal multiplexing sensor, the preparation method comprising the preparation of a support layer, the preparation of a thermocouple, the preparation of a light absorbing layer, and the preparation of a suspended structure by dry etching, and the method comprises the following steps: Step S1, select a device processing substrate to prepare a support layer; the size of the device processing substrate is in the millimeter range, with a typical size of 5mm×5mm, and the size of the MEMS sensor can be as small as 1.0mm×1.0mm, with a thickness ranging from tens of microns to hundreds of microns, and a square or round shape.

[0028] Step S2, using micro-nano processing technology to prepare a thermocouple, an infrared absorption layer and a rigid packaging layer; the micro-nano processing means include but are not limited to photolithography, FIB etching, electron beam etching, etc., to process the substrate into a hollow cup structure; Step S3, preparing the suspension structure using micro-nano processing technology; Step S4, multiple sensing element connection modes are used for different measurement purposes. Pure pressure measurement adopts Wheatstone bridge connection, and temperature / heat measurement adopts sensing element series connection.

[0029] Furthermore, step 1 includes the following steps: Step S11, silicon substrate processing, cleaning the silicon wafer surface by RAC standard cleaning process; Step S12: preparing a support layer by using LPCVD or PECVD to prepare a silicon oxide film and a silicon nitride film.

[0030] Furthermore, step 2 of preparing the thermocouple, the infrared absorption layer and the rigid packaging layer by using micro-nano processing technology comprises the following steps: Step 21, preparing bismuth telluride and antimony telluride thermocouples by photolithography and magnetron sputtering; Step 22, evaporating a black gold infrared absorption layer on the hot junction area of ​​the thermocouple; Step 23, depositing an aluminum oxide rigid packaging layer on the surface.

[0031] The preparation method of the pressure and heat multiplexing sensor is further described below with reference to the embodiments.

[0032] Example 1 In this embodiment, the method for preparing the microbridge suspension structure of the pressure and thermal multiplexing sensor includes the following steps: Step S3-1-1, using a standard RAC cleaning process, ultrasonically clean the single crystal silicon substrate in isopropanol, acetone, alcohol and ultrapure water for 15 minutes in sequence, and then dry it.

[0033] Step S3-1-2, depositing a 180nm-220nm thick silicon nitride support layer on a single crystal polished silicon wafer by plasma enhanced chemical vapor deposition on a silicon substrate.

[0034] Step S3-1-3, prepare a thermocouple by a stripping method, prepare strip bismuth telluride by a first photolithography and magnetron sputtering, and prepare strip antimony telluride by a second alignment photolithography and magnetron sputtering, wherein the photoresist adopts a LOR / S1805 double-layer glue structure, and the thickness of bismuth telluride and bismuth antimonide is 600nm-800nm.

[0035] Step S3-1-4, using a stripping method to prepare a black gold infrared absorption layer in the hot junction area of ​​the thermocouple, wherein the black gold absorption layer is prepared by thermal evaporation of gold in a nitrogen atmosphere, and the thickness of the infrared absorption layer is between 500-1000nm.

[0036] Step S3-1-5, using magnetron sputtering method to deposit a 1200-1500nm thick aluminum oxide rigid packaging layer on the detector surface.

[0037] Step S3-1-6, etching silicon using photolithography and ICP etching processes to form a microbridge suspension structure of the pressure and thermal multiplexing sensor.

[0038] Example 2 In this embodiment, the method for preparing the microbridge suspension structure of the pressure and thermal multiplexing sensor includes the following steps: Step S31, using a standard RAC cleaning process, ultrasonically cleaning the silicon oxide substrate in isopropanol, acetone, alcohol and ultrapure water for 15 minutes in sequence, and drying.

[0039] Step S32, depositing a 180nm-220nm thick silicon nitride support layer on the cobalt oxide substrate by low pressure chemical vapor deposition on the silicon substrate.

[0040] Step S33, preparing a thermocouple by a stripping method, preparing strip copper by a first photolithography and magnetron sputtering, and preparing strip constantan by a second alignment photolithography and magnetron sputtering; wherein the photoresist adopts a LOR / S1805 double-layer glue structure, and the thickness of copper and constantan is 1500-1800nm.

[0041] Step S34, using photolithography and spin coating methods to prepare a graphene black paint infrared absorption layer in the hot junction area of ​​the thermocouple; wherein the graphene black paint coating is prepared by mechanical stripping, and the thickness of the infrared absorption layer is between 1000-1200nm.

[0042] Step S35, using magnetron sputtering to deposit a 1200-1500 nm thick aluminum oxide rigid packaging layer on the detector surface.

[0043] Step S36, etching silicon using photolithography and ICP etching processes to form a microbridge suspension structure of the pressure and thermal multiplexing sensor.

[0044] The pressure and heat multiplexed sensor of the microbridge suspension structure prepared by the above method is connected through a variety of sensing elements for different measurement purposes. Pure pressure measurement adopts Wheatstone bridge connection, and temperature / heat measurement adopts thermocouple series connection.

[0045] Application Example 1 When the pressure and heat multiplexed sensor prepared by the above method is used to measure pressure, four thermocouple pairs evenly distributed are taken and Figure 4 The connection is a Wheatstone bridge, where the positive and negative signs represent the positive and negative poles of the thermocouple, and the arrow indicates that the sensing element is a variable resistor whose resistance changes with pressure. The change of the voltage value with pressure is measured at the output end, and calibrated by a standard pressure source, it becomes a pressure sensor.

[0046] Application Example 2 When the pressure and heat multiplexed sensor prepared by the above method is used for temperature / heat measurement, the positive and negative ends of the thermocouple are connected end to end to form a series connection to amplify the output voltage; Figure 3 The sensor elements are connected in series as shown. To achieve multiplexing, this technology uses thermocouples as force and heat sensing elements. In addition to measuring force and temperature signals at the same time, different connection modes can also be used to achieve better force and temperature measurement.

[0047] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A pressure and heat multiplexing sensor, characterized in that: It has a suspended thermopile and is able to measure pressure and temperature simultaneously.

2. The pressure and heat multiplexing sensor according to claim 1, characterized in that: The pressure and heat multiplexing sensor adopts a bridge structure, which includes a substrate, a support layer, a thermopile, an infrared absorption layer and a rigid packaging layer from bottom to top; the bridge structure adopts a microbridge suspension structure, and the thermopile adopts a multi-stage series structure. The hot junction area of ​​the thermopile is located in the central area of ​​the microbridge suspension structure, and the cold junction area of ​​the thermopile is located on the top support layer of the substrate.

3. The pressure and heat multiplexing sensor according to claim 2, characterized in that: The central area of ​​the microbridge suspension structure is etched from the back side by isotropic dry etching to form a cavity structure.

4. The pressure and heat multiplexing sensor according to claim 3, characterized in that: The infrared absorption layer covers the central area of ​​the microbridge suspension structure.

5. The pressure and heat multiplexing sensor according to claim 2, characterized in that: The rigid packaging layer covers the upper surface of the sensor.

6. The pressure and heat multiplexing sensor according to claim 2, characterized in that: A thermopile is a thermocouple or a circular array of thermocouples.

7. The pressure and heat multiplexing sensor according to claim 6, characterized in that: The substrate is any single crystal silicon substrate or silicon oxide substrate.

8. The pressure and heat multiplexing sensor according to claim 5, characterized in that: The supporting layer is a silicon nitride film grown by plasma enhanced chemical vapor deposition, or a silicon oxide and silicon nitride film.

9. The pressure and heat multiplexing sensor according to claim 1, characterized in that: The rigid packaging layer adopts an alumina ceramic packaging layer with high light transmittance.

10. A method for preparing the pressure and thermal multiplex sensor according to any one of claims 1 to 9, characterized in that: It includes the following steps: Step S1, selecting a device to process a substrate and preparing a support layer; Step S2, using micro-nano processing technology to prepare a thermocouple, an infrared absorption layer and a rigid packaging layer; the micro-nano processing means include but are not limited to photolithography, FIB etching, electron beam etching, etc., to process the substrate into a hollow cup structure; Step S3, preparing the suspension structure using micro-nano processing technology; Step S4, multiple sensing element connection modes are used for different measurement purposes. Pure pressure measurement uses Wheatstone bridge connection, and temperature / heat measurement uses sensing element series connection.

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