A pressure and heat multiplexed sensor and method of making the same

Abstract

The application provides a pressure and heat multiplexing sensor and a preparation method thereof, the pressure and heat multiplexing sensor has a suspended structure thermoelectric pile and can simultaneously measure pressure and temperature. Further, the pressure and heat multiplexing sensor adopts a bridge structure, from bottom to top, a substrate, a support layer, a thermoelectric pile, an infrared absorption layer and a rigid packaging layer, the thermoelectric pile adopts a multi-stage series structure, the hot junction area of the thermoelectric pile is located in the center area of the micro-bridge suspended structure, the cold junction area is located on the support layer on the top of the substrate, the center area of the micro-bridge suspended structure is formed into a cavity structure by isotropic dry etching from the back, the infrared absorption layer covers the center area of the micro-bridge suspended structure, and the rigid packaging layer covers the upper surface of the sensor. The application can simultaneously measure pressure and temperature, is manufactured by using standard CMOS process general materials and manufacturing methods, meets the integrated and miniaturized demand of the intelligent sensing field, and is expected to be widely applied.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of pressure detection, and more particularly to a pressure and heat multiplexing sensor and a preparation method thereof. BACKGROUND

[0002] A pressure sensor is a device or apparatus that can sense a pressure signal and convert the pressure signal into an electrical signal according to a certain rule. The pressure sensor is usually composed of a pressure sensitive element and a signal processing unit. According to different types of test pressure, the pressure sensor can be divided into gauge pressure sensors, differential pressure sensors and absolute pressure sensors. The pressure sensor is the most commonly used sensor in industrial practice, and is widely used in various industrial control environments, involving water conservancy and hydropower, railway transportation, intelligent building, production automatic control, aerospace, military, petrochemical, oil well, power, ship, machine tool, pipeline and many other industries.

[0003] Silicon-based pressure sensors are the mainstream of pressure sensors. They use polycrystalline silicon / silicon / carbonized silicon as the substrate, adopt microsystem manufacturing process, prepare an empty cup structure, along a specific crystal direction on a single crystal silicon wafer, and are doped to form a sensitive element. Subsequently, based on the Wheatstone bridge, the change in resistance is converted into an electrical signal for output, realizing the measurement of external pressure. The silicon-based pressure sensing technology cannot be used for heat sensing. In the silicon-based pressure sensing technology, temperature drift is suppressed by the bridge, temperature is measured by auxiliary equipment, and the algorithm is used to compensate, which inevitably reduces the device integration.

[0004] The prior art uses a thermocouple as a radiation heat sensor, and the device structure is similar to that of a silicon piezoresistive sensor. A heat blocking layer is used to control the direction of heat transfer, and a heat absorbing element is used as a working element to convert light into heat and a thermocouple to convert heat into electricity. It is more complex than a piezoresistive silicon sensor. This prior art solution is relatively complex, difficult, and requires high equipment, with multiple challenges coexisting, and the overall controllability is greatly reduced, and it cannot be used for pressure sensing.

[0005] Based on the needs of industrial practice, a pressure and heat multiplexing sensor technology is needed. SUMMARY

[0006] Based on the technical problems existing in the prior art, the present application provides a pressure and heat multiplexing sensor and a preparation method thereof, aiming to solve the problems of the prior art silicon-based pressure sensor that cannot be used for heat sensing, and the relatively complex technology, high difficulty, and high equipment requirement, and has the advantages of relatively simple structure, temperature and pressure measurement, strong function, easy production, and good controllability.

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

[0008] Further, the pressure and heat multiplexing sensor adopts a bridge structure, from bottom to top, in sequence, a substrate, a support layer, a thermocouple, an infrared absorption layer and a rigid packaging layer; the bridge structure adopts a micro-bridge suspended structure, the thermocouple adopts a multi-stage series structure, the thermocouple hot junction is located in the center region of the micro-bridge suspended structure, and the thermocouple cold junction is located on the support layer on the top of the substrate.

[0009] Preferably, the center region of the micro-bridge suspended structure is formed into a cavity structure by isotropic dry etching from the back.

[0010] Further, the infrared absorption layer covers the center region of the micro-bridge suspended structure, and the rigid packaging layer covers the upper surface of the entire sensor.

[0011] More preferably, the substrate is an arbitrary single crystal silicon substrate or a 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, and the rigid packaging layer adopts an alumina ceramic packaging layer with high light transmittance.

[0012] According to a second aspect of the technical solution of the present application, a preparation method of the pressure and heat multiplexing sensor is provided, which comprises the following steps:

[0013] Step S1, selecting a device processing substrate to prepare a support layer;

[0014] 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 includes, but is not limited to, photolithography, FIB etching, electron beam etching, etc., and the substrate is processed into a hollow cup structure;

[0015] Step S3, using micro-nano processing technology to prepare a suspended structure;

[0016] Step S4, connecting a plurality of sensing elements in different ways for different measurement purposes, using a Wheatstone bridge connection for pure pressure measurement, and using a series connection of sensing elements for temperature / heat measurement.

[0017] Compared with the prior art, the pressure and heat multiplexing sensor preparation method and system of the present application have the following beneficial effects:

[0018] (1) The pressure and heat multiplexing sensor structure proposed by the present application is relatively simple, can simultaneously measure temperature and pressure, has stronger functions, is easy to manufacture, and has good controllability;

[0019] (2) The pressure and heat multiplex sensor prepared by the application has simple structure, easy processing, low requirement for materials and equipment, and can realize rapid, efficient and low-cost mass production.

[0020] (3) The pressure and heat multiplex sensor prepared by the application can measure pressure and temperature at the same time, greatly facilitating industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 It is a top view of a schematic diagram of the pressure and heat multiplex sensor according to the present application;

[0023] Figure 2 It is a side view of a schematic diagram of the pressure and heat multiplex sensor according to the present application;

[0024] Figure 3 It is a schematic diagram of a series connection method of the sensing element according to the present application;

[0025] Figure 4 It is a bridge connection diagram of the sensing element according to the present application. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0027] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element. The embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and embodiments.

[0028] It should be understood that the terms "length", "width", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like specify relative or positional relationships based on the orientation or position shown in the drawings, and are used only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0029] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is more than two, unless otherwise specifically limited.

[0030] The present application provides a pressure and heat multiplexing sensor and a preparation method thereof, the pressure and heat multiplexing sensor has a suspended structure thermoelectric pile and can measure pressure and temperature at the same time. Further, the pressure and heat multiplexing sensor adopts a bridge structure, from bottom to top in turn is base, support layer, thermoelectric pile, infrared absorption layer and rigid packaging layer; the bridge structure adopts a micro-bridge suspended structure, the thermoelectric pile adopts a multi-stage series structure, the thermoelectric pile hot junction area is located in the micro-bridge suspended structure central region, the cold junction area is located on the top of the base support layer, the micro-bridge suspended structure central region is formed by isotropic dry etching from the back cavity structure, the infrared absorption layer covers the micro-bridge suspended structure central region, and the rigid packaging layer covers the entire sensor upper surface. The present application can measure pressure and temperature at the same time, and is manufactured by using standard CMOS process general material and manufacturing method, meets the integration and miniaturization demand of intelligent sensing field, and is expected to be widely applied.

[0031] The micro-bridge suspension structure of the present application is a combination of micro-bridge structure and suspension structure. The micro-bridge structure of the present application is a structure design in micro-nano scale. The micro-bridge structure is made of 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, certain elasticity and flexibility. The micro-bridge structure of the present application can be used in sensors for measuring physical quantities such as pressure, strain, displacement, etc. When subjected to external force or pressure, the micro-bridge structure will deform, and by measuring the deformation, the required physical quantity information can be obtained. At the same time, the micro-bridge structure of the present application can be used as a micro-heater, which expands by electricity to control micro-fluids, temperature control, etc. Further, the suspension structure of the present application adopts an elastic cantilever structure, which provides operation space for micro-scale mechanical operations such as sensing, suspension and manipulation. The present application creatively combines micro-bridge structure and suspension structure together to realize pressure and heat multiplexing sensing and detection.

[0032] In order to illustrate the technical solutions of the present application, specific embodiments and drawings will be described below.

[0033] As shown in Figures 1-2 The present application provides a pressure and heat multiplexing sensor, which adopts a micro-bridge structure. The entire pressure and heat multiplexing sensor includes five parts: a substrate, a support layer, a thermoelectric pile, an infrared absorption layer and a rigid packaging layer. In a preferred embodiment, the thermoelectric pile is a thermocouple or a thermocouple ring array, the infrared absorption layer serves as a heat absorption layer, and the rigid packaging layer serves as a protective layer. The thermocouple ring array is a pair of thermocouples arranged around a central axis. Preferably, the thermocouple pairs in the thermocouple ring array are uniformly and symmetrically arranged. The bridge structure adopts a micro-bridge suspension structure.

[0034] In an embodiment, a dry etching process is used to prepare a suspension structure on the back of the substrate. Preferably, the suspension structure is a micro-bridge suspension structure, and the support layer carries the thermocouple and the infrared absorption layer. The thermoelectric pile adopts a multi-stage series structure, and the thermoelectric pile hot junction region is located in the center region of the micro-bridge suspension structure. The thermoelectric pile cold junction region is located on the top of the substrate support layer. The infrared absorption layer covers the center region of the micro-bridge suspension structure and is used to absorb radiant heat. The rigid packaging layer is located on the upper surface of the detector and serves to protect the infrared absorption layer and improve the mechanical strength of the sensor. The structural advantage of the pressure and heat multiplexing sensor of the present application lies in the use of the suspension structure, the infrared absorption layer and the rigid packaging layer, which makes the detector have excellent infrared light absorption capacity and good mechanical properties, so that the detector can measure temperature and pressure at the same time.

[0035] Further, 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 thermocouple is made of bismuth telluride and antimony telluride or copper-constantan and the like. The rigid packaging layer is an alumina ceramic packaging layer with high light transmittance. The materials of the detector layers include but are not limited to the above materials.

[0036] The mechanical and thermal compound sensor provided by the application adopts general materials and manufacturing techniques compatible with CMOS, and the single-sided suspended structure is prepared by backside silicon dry etching process. The backside etching does not need a top protection layer, which not only simplifies the preparation process of the detector and reduces the manufacturing cost, but also avoids surface pollution and etching damage.

[0037] Further, the application provides a preparation method of a pressure and thermal multiplexing sensor, which comprises the preparation of a support layer, the preparation of a thermocouple, the preparation of a light absorbing layer, and the preparation of a dry etching suspended structure, which comprises the following steps:

[0038] Step S1, a device processing substrate is selected to prepare a support layer; the device processing substrate has a size of millimeter level, and a typical size of 5mm*5mm. The size of the MEMS sensor can be as small as 1.0mm*1.0mm, and the thickness ranges from several tens of microns to several hundred microns, and the shape is square or circular.

[0039] Step S2, a thermocouple, an infrared absorbing layer and a rigid packaging layer are prepared by micro-nano processing technology; the micro-nano processing means include but are not limited to photolithography, FIB etching, electron beam etching and the like, and the substrate is processed into a hollow cup structure;

[0040] Step S3, a suspended structure is prepared by micro-nano processing technology;

[0041] Step S4, a variety of sensing element connection modes are used for different measurement purposes, a Wheatstone bridge connection is used for pure pressure measurement, and a sensing element series connection mode is used for temperature / thermal measurement.

[0042] Further, step 1 comprises the following steps:

[0043] Step S11, silicon substrate treatment, the surface of the silicon wafer is cleaned by RAC standard cleaning process;

[0044] Step S12, support layer preparation, silicon oxide film and silicon nitride film are prepared by LPCVD or PECVD.

[0045] Further, step 2 of preparing the thermocouple, the infrared absorbing layer and the rigid packaging layer by micro-nano processing technology comprises the following steps:

[0046] Step 21, bismuth telluride and antimony telluride thermocouples are prepared by photolithography and magnetron sputtering.

[0047] Step 22: Evaporate a black gold infrared absorption layer in the thermocouple junction region;

[0048] Step 23: Deposit a rigid aluminum oxide encapsulation layer on the surface.

[0049] The following examples further illustrate the fabrication method of the pressure and heat multiplexing sensor.

[0050] Example 1

[0051] In this embodiment, the method for fabricating the microbridge suspension structure of the pressure and heat multiplexing sensor includes the following steps:

[0052] Step S3-1-1: Using the standard RAC cleaning process, the monocrystalline silicon substrate is ultrasonically cleaned for 15 minutes in isopropanol, acetone, alcohol and ultrapure water in sequence, and then dried.

[0053] Step S3-1-2: A silicon nitride support layer with a thickness of 180nm-220nm is deposited on a silicon substrate using plasma-enhanced chemical vapor deposition on a single-crystal polished silicon wafer.

[0054] In step S3-1-3, a thermocouple is prepared by a stripping method, and strip-shaped bismuth telluride is prepared by a first photolithography and magnetron sputtering, and strip-shaped antimony telluride is prepared by a second alignment photolithography and magnetron sputtering. The photoresist adopts a LOR / S1805 double-layer adhesive structure, and the thickness of bismuth telluride and bismuth antimony is 600nm-800nm.

[0055] Step S3-1-4: A black gold infrared absorption layer is prepared in the hot junction region of the thermocouple by a stripping method. The black gold absorption layer is prepared by thermal evaporation of gold under a nitrogen atmosphere, and the thickness of the infrared absorption layer is between 500-1000 nm.

[0056] Step S3-1-5: A rigid alumina encapsulation layer with a thickness of 1200-1500 nm is deposited on the detector surface using magnetron sputtering.

[0057] Step S3-1-6: Silicon is etched using photolithography and ICP etching processes to form a microbridge suspension structure for the pressure and thermal multiplexing sensor.

[0058] Example 2

[0059] In this embodiment, the method for fabricating the microbridge suspension structure of the pressure and heat multiplexing sensor includes the following steps:

[0060] Step S31: Using the standard RAC cleaning process, the silicon oxide substrate is ultrasonically cleaned in isopropanol, acetone, alcohol and ultrapure water for 15 minutes in sequence, and then dried.

[0061] Step S32: A silicon nitride support layer with a thickness of 180nm-220nm is deposited on a silicon substrate using low-pressure chemical vapor deposition on a cobalt oxide substrate.

[0062] Step S33: Thermocouple is prepared by stripping method, strip copper is prepared by first photolithography and magnetron sputtering, and strip constantan is prepared by second alignment photolithography and magnetron sputtering; wherein, the photoresist adopts LOR / S1805 double-layer adhesive structure, and the thickness of copper and constantan is 1500-1800nm.

[0063] Step S34: A graphene black paint infrared absorption layer is prepared in the hot junction region of the thermocouple using photolithography and spin coating methods; wherein, the graphene black paint coating is prepared by mechanical exfoliation, and the thickness of the infrared absorption layer is between 1000-1200 nm.

[0064] Step S35: A rigid alumina encapsulation layer with a thickness of 1200-1500 nm is deposited on the detector surface using magnetron sputtering.

[0065] Step S36: Silicon is etched using photolithography and ICP etching processes to form a microbridge suspension structure for the pressure and thermal multiplexing sensor.

[0066] The pressure and heat multiplexing sensor of the microbridge suspension structure prepared by the above method is used for different measurement purposes by connecting various sensing elements. For simple pressure measurement, a Wheatstone bridge is used, and for temperature / heat measurement, a thermocouple is connected in series.

[0067] Application Example 1

[0068] When using the pressure and thermal multiplexing sensor prepared by the above method to measure pressure, take four evenly distributed thermocouple pairs and arrange them according to... Figure 4 The connection is a Wheatstone bridge, where the positive and negative signs indicate the positive and negative terminals of the thermocouple, and the arrow indicates that the sensing element is a variable resistor whose resistance changes with pressure. The voltage change with pressure is measured at the output terminal, and calibrated using a standard pressure source, thus forming a pressure sensor.

[0069] Application Example 2

[0070] When using the pressure and heat multiplexing sensor prepared by the above method for temperature / heat measurement, the positive and negative terminals of the thermocouple are connected end-to-end to form a series connection, thereby amplifying the output voltage; for example... 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 simultaneously measuring force and temperature signals, different connection modes can be used to achieve better force and temperature measurement.

[0071] The above are merely 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 within the protection scope of the present invention.

Claims

1. A pressure and heat multiplexing sensor, characterized in that, It features a suspended thermopile structure and can simultaneously measure pressure and temperature; The pressure and thermal multiplexing sensor adopts a bridge structure, which consists of a substrate, a support layer, a thermopile, an infrared absorption layer, and a rigid encapsulation 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 region of the thermopile is located in the central region of the microbridge suspension structure, and the cold junction region of the thermopile is located on the support layer at the top of the substrate. The central region of the microbridge suspension structure is etched from the back side using isotropic dry etching to form a cavity structure.

2. The pressure and heat multiplexing sensor according to claim 1, characterized in that, An infrared absorption layer covers the central region of the microbridge suspension structure.

3. The pressure and heat multiplexing sensor according to claim 1, characterized in that, A rigid encapsulation layer covers the upper surface of the sensor.

4. The pressure and heat multiplexing sensor according to claim 1, characterized in that, A thermopile is a thermocouple or a ring array of thermocouples.

5. The pressure and heat multiplexing sensor according to claim 4, characterized in that, The substrate can be any single-crystal silicon substrate or silicon oxide substrate.

6. The pressure and heat multiplexing sensor according to claim 3, characterized in that, The support layer is a silicon nitride thin film grown by plasma-enhanced chemical vapor deposition, or a silicon oxide and silicon nitride thin film.

7. The pressure and heat multiplexing sensor according to claim 1, characterized in that, The rigid encapsulation layer uses an alumina ceramic encapsulation layer with high light transmittance.

8. A method for preparing the pressure and heat multiplexing sensor according to any one of claims 1-7, characterized in that, It includes the following steps: Step S1: Select a device processing substrate and prepare a support layer; Step S2: Thermocouple, infrared absorption layer and rigid packaging layer are fabricated using micro-nano fabrication technology; micro-nano fabrication methods include, but are not limited to, photolithography, FIB etching, electron beam etching, etc., to process the substrate into a hollow cup structure; Step S3: Prepare the suspension structure using micro-nano fabrication technology; Step S4: Various sensing element connection methods are used for different measurement purposes. For simple pressure measurement, a Wheatstone bridge connection is used, while for temperature / heat measurement, the sensing elements are connected in series.

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