CN116499517A - CMOS MEMS integrated flow, gas/humidity sensor - Google Patents
CMOS MEMS integrated flow, gas/humidity sensor Download PDFInfo
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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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- G—PHYSICS
- G01—MEASURING; TESTING
- G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
- G01D21/00—Measuring or testing not otherwise provided for
- G01D21/02—Measuring two or more variables by means not covered by a single other subclass
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
- G01F1/6845—Micromachined devices
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/68—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using thermal effects
- G01F1/684—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow
- G01F1/688—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element
- G01F1/69—Structural arrangements; Mounting of elements, e.g. in relation to fluid flow using a particular type of heating, cooling or sensing element of resistive type
- G01F1/692—Thin-film arrangements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
- G01F15/08—Air or gas separators in combination with liquid meters; Liquid separators in combination with gas-meters
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/121—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid for determining moisture content, e.g. humidity, of the fluid
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
- G01N27/128—Microapparatus
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- G01N27/228—Circuits therefor
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Abstract
The invention relates to a CMOS MEMS integrated flow and gas/humidity sensor, in particular to a CMOS MEMS integrated flow and gas/humidity sensor and a manufacturing method thereof; belongs to the field of sensors. The invention aims to overcome the defects of the prior art, fill the blank in the field, realize the function of simultaneously detecting the gas flow and the gas/humidity by a single chip, and provide a CMOS MEMS integrated flow, gas/humidity sensor and a manufacturing method thereof; the sensor fully utilizes the heat of the heating resistor of the flow sensing part, greatly improves the energy utilization rate, and has the advantages of low power consumption, high response speed and low hysteresis; the Post-CMOS process without mask operation is adopted, so that complex photoetching steps are avoided, the Post-processing complexity of the whole device is effectively reduced, and the Post-processing efficiency of the whole Post-CMOS is greatly improved.
Description
Technical Field
The invention relates to a CMOS MEMS integrated flow and gas/humidity sensor, in particular to a CMOS MEMS integrated flow and gas/humidity sensor and a manufacturing method thereof; belongs to the field of sensors.
Background
Flow sensors are vital in production life and scientific laboratory metering, such as sensing environmental flow, industrial gas flow monitoring, flow sensing in biomedical applications, and marine hydrodynamic sensing. While advances in MEMS technology have made it possible to fabricate complex sensors, many studies have demonstrated that MEMS processes can be successfully applied to fabricate a variety of flow and direction sensing sensors, and that they can be mass produced at low cost. In addition to high requirements for sensitivity in detecting fluid parameters (flow rate, direction, etc.), flow sensors are now in demand for low power consumption, low cost, long-term stability. In various applications, flow sensors are required to measure the speed and direction of liquid and gas flow, including determination of flow patterns, measurement of wall shear stress, viscosity and density measurements. The measured flow rate may be affected by the speed, pressure, temperature or chemical composition of the system. Thus, flow sensing devices are typically based on direct detection of volume, mass, velocity, or multiparameter detection. The MEMS flow sensor belongs to micro equipment, can realize high-resolution detection, has a great application prospect compared with sensing equipment of a conventional principle, and is applied to the field of high precision, navigation of an underwater vehicle, detection of an underwater target, biomedical treatment, environmental monitoring and the like.
MEMS flow sensors can be broadly divided into three categories according to principles: thermal flow sensors, piezoresistive flow sensors, and piezoelectric flow sensors. Wherein thermal flow sensors are generally composed of two basic parts, namely a heater and a sensing element. The sensing element detects a change in heat transfer between the heater and the fluid, and uses the heat transfer intensity to determine the flow rate of the fluid. Thermal flow sensors enable high sensitivity and high accuracy measurements and low output signal drift relative to other types of flow sensors. Furthermore, this type of sensor has the advantage of enabling flow rate measurements to be made on miniature components that do not rely on any mechanical movement, which reduces wear on the equipment and has a longer service life. Although the MEMS technology can adopt a flexible processing method and can select a wide range of materials, it is difficult to directly interconnect with the circuit portion, so that the overall size of the test microsystem is limited to a certain extent, and the processing method is complex and it is difficult to realize low-cost mass production; with the rapid development of CMOS semiconductor technology, the mature CMOS processing technology has shown great advantages in the sensor field, not only has the device size been further reduced, but also low-cost mass production of the sensor has become possible, and thus CMOS MEMS technology has been widely used in recent years for manufacturing low-cost micro flow sensors.
The gas sensor is a device for detecting the concentration of gas and is widely applied to the fields of food storage, electronic manufacturing, industrial automation, agricultural planting, textile production, home monitoring, medical experiments and the like. Resistive gas sensors and capacitive gas sensors are the two most common forms of gas sensing, and the resistive gas sensor consists of a sensitive membrane, a heater and electrodes. CMOS platforms provide useful materials for fabricating heaters and electrodes and use additional materials (typically metal oxide semiconductor materials) as sensitive films. The heater activates the sensitive film material to change its resistivity when adsorbing (or desorbing) gas molecules, so that the gas concentration can be detected by the change of the resistance value. Capacitive gas sensors are often used for humidity, i.e. water vapor detection. The humidity sensitive film material is filled on the capacitive humidity sensing structure, and when the humidity sensitive film material adsorbs (or desorbs) moisture, the change of dielectric constant between the capacitive polar plates is caused, so that the humidity of the gas is detected through the change of capacitance value.
However, most of the existing CMOS MEMS flow sensors or gas/humidity sensors can only singly detect flow or gas/humidity, and have relatively high power consumption, in practical applications, it is often required to detect the important parameters of flow and gas/humidity simultaneously, and the central heating resistor of the thermal gas flow sensor happens to activate the sensitive film material of the gas sensing structure, so that on the basis of fully utilizing the CMOS MEMS process, the structure of the gas sensor is placed above the central heating resistor of the thermal flow sensor to realize the simultaneous detection of flow and gas/humidity, which is a feasible scheme; compared with the traditional CMOS MEMS thermal flow sensor, the temperature can be higher by accurately designing the parameters of the heating resistor of the flow sensor, so that the performance of the flow sensor can be improved, and the sensing efficiency of the gas sensor can be improved at the same time; in addition, the heat of the heating resistor is fully utilized, the parameter of the heating resistor is designed to achieve proper response time, and square wave voltage signals with the frequency higher than the response frequency of the heating resistor are used for supplying power to the heating resistor, so that the power consumption of the sensor is greatly reduced, and the hysteresis of gas detection is reduced.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, fill the blank in the field, realize the function of measuring flow and gas/humidity simultaneously by a single chip, and provide a CMOS-MEMS monolithic integrated flow, gas/humidity sensor and a manufacturing method thereof; the sensor fully utilizes the heat of the heating resistor of the flow sensor, improves the energy utilization rate, adopts a Post-CMOS process without a mask, avoids complex photoetching steps, and greatly improves the Post-processing efficiency of the whole Post-CMOS. The sensing part adopts a suspension structure, and has the advantages of high response speed and low heat dissipation.
The aim of the invention is achieved by the following technical scheme.
A CMOS MEMS integrated flow, gas/humidity sensor comprises a silicon substrate layer and a silicon dioxide structure layer, wherein the silicon dioxide structure layer is arranged above the silicon substrate layer; the silicon dioxide structure layer comprises PAD areas arranged at two ends and a flow sensor area and a gas/humidity sensor area which are arranged in the center; the silicon dioxide material and the metal material in the PAD area are overlapped and distributed, and the metal via penetrates through other metal layers except the top metal layer; the flow sensor area comprises a heating resistor, a first thermistor and a second thermistor which are distributed on two sides of the heating resistor, the first thermistor and the second thermistor are arranged in a silicon dioxide material, and the heating resistor, the first thermistor and the second thermistor are integrally suspended above the cavity; the gas/humidity sensor region includes a heating resistor disposed in a silicon dioxide material and a gas/humidity sensing electrode comprised of a bottommost metal disposed over the heating resistor and a sensitive film material filled or deposited on the gas/humidity sensing electrode.
A preparation method of a CMOS MEMS integrated flow and gas/humidity sensor adopts a Post-CMOS processing method without mask operation, comprising the following steps:
step 1: designing a CMOS bare chip by adopting a 0.18um 1P6M process, designing a reasonable metal layer pattern and metal via in a PAD area, and filling silicon dioxide materials between the two metal layers at the top, so that a natural mask of the PAD area is formed during metal etching to protect the structure of the CMOS bare chip; the method comprises the steps that a reasonable polysilicon layer pattern is designed in a flow sensor area to form a heating resistor, a first thermistor and a second thermistor of the flow sensor; a reasonable metal layer pattern and metal via are designed in the flow sensor area, so that a layer of thin silicon dioxide material is reserved above the heating resistor, the first thermistor and the second thermistor to form natural masks of the heating resistor, the first thermistor and the second thermistor, and the via is directly connected with the silicon substrate to form a channel for subsequent silicon etching; the electrode structure of the gas/humidity sensor is formed by utilizing a metal layer pattern and metal via which are reasonably designed on the heating resistor of the flow sensor by using bottom metal;
step 2: siO Using RIE on the CMOS die obtained in step 1 2 Etching to form a groove and a microcavity, so that the top-layer metal aluminum and the substrate silicon are exposed;
step 3: carrying out metal aluminum etching on the chip obtained in the step 2, and removing the top metal aluminum;
step 4: siO is carried out on the chip obtained in the step 3 by adopting RIE 2 Etching to remove SiO on the surface layer 2 And exposing the centrally located heating electricityElectrode structure of gas/humidity sensor above resistance;
step 5: performing DRIE silicon etching on the chip obtained in the step 4, wherein the SiO is the same as that of the chip obtained in the step 4 2 And forming a silicon trench with a high aspect ratio by using the metal layer as a mask of silicon;
step 6: xeF is carried out on the chip obtained in the step 5 2 Isotropically dry etching to release the sensor suspension structure;
step 7: and (3) filling or depositing the sensitive film material on the chip obtained in the step (6) to fill or deposit the sensitive film material on the electrode structure of the gas/humidity sensor.
The beneficial effects are that:
1. according to the invention, the gas/humidity sensing structure is arranged above the central heating resistor of the flow sensing structure, so that the function of simultaneously detecting flow and gas/humidity is realized, the heat of the heating resistor is fully utilized to activate the sensitive film material of the gas/humidity sensor, and the energy utilization rate is greatly improved.
2. According to the invention, the parameters of the heating resistor of the flow sensor are accurately designed to enable the heating resistor to reach higher temperature, so that the performance of the flow sensor can be improved, and the sensing efficiency of the gas/humidity sensor can be improved at the same time; in addition, by designing parameters of the heating resistor to achieve proper response time and using square wave voltage signals with frequency higher than the response frequency of the heating resistor to supply power, the power consumption of the sensor can be greatly reduced and hysteresis of gas/humidity detection can be reduced.
3. According to the invention, the metal layer pattern is designed to be a mask of a natural polysilicon layer, so that all functional components of the sensing device can be etched without a mask plate and without damage, and complex photoetching steps are avoided.
4. The integration of a single-chip multifunctional sensor is realized, and the cost of the sensor is greatly reduced due to the integrated design and the subsequent simple processing technology; the invention greatly improves the utilization ratio of energy, has the advantages of high stability, high sensitivity, low heat dissipation and low hysteresis, has small volume and high integration level of the single-chip flow and gas/humidity integrated sensor, can effectively solve the problems of large volume and poor suitability caused by simple stacking of the prior single-function sensor, and has the advantages of low energy utilization ratio, high cost, larger heat dissipation, relatively limited sensitivity and response speed of the gas flow and gas/humidity sensor in the market, and has low cost, simple preparation and processing mode and convenient mass production.
Drawings
FIG. 1 is a schematic diagram of the three-dimensional structure of a CMOS MEMS integrated flow, gas/humidity sensor of the present invention; wherein (a) is a capacitive gas/humidity sensing electrode structure and (b) is a resistive gas/humidity sensing electrode structure;
FIG. 2 is a flow chart of the fabrication of the CMOS MEMS integrated flow, gas/humidity sensor of the present invention; wherein figure a is a designed CMOS die, figure b shows the silicon dioxide etch of the CMOS die with RIE to form trenches and microcavities, figure c shows the metal layer etch, figure d shows the silicon dioxide etch leaving the gas/humidity sensor electrode structure bare, figure e shows the DRIE etch of silicon to form trenches on the substrate, figure f shows XeF 2 Etching to release the suspension structure, wherein the graph g shows filling of the sensitive film material;
fig. 3 is a cross-sectional view of a CMOS MEMS integrated flow, gas/humidity sensor of the present invention.
Wherein: a 1-Si substrate; a 2-SiO2 structural layer; 3-a first thermistor; 4-heating resistance; 5-a second thermistor; 6-cavity; 7-gas/humidity sensing electrode structure; 8-sensitive membrane material.
Detailed Description
For a better description of the objects and advantages of the present invention, the following description will be given with reference to the accompanying drawings and examples.
See fig. 1 and 3: the CMOS MEMS integrated flow and gas/humidity sensor disclosed by the embodiment comprises a silicon substrate layer 1 and a silicon dioxide structure layer 2, wherein the silicon dioxide structure layer 2 is arranged above the silicon substrate layer 1; the silicon dioxide structure layer 2 comprises PAD areas arranged at two ends and a flow sensor area and a gas/humidity sensor area which are arranged in the center; the silicon dioxide material and the metal material in the PAD area are overlapped and distributed, and the metal via penetrates through other metal layers except the top metal layer; the flow sensor area comprises a heating resistor 4, a first thermistor 3 and a second thermistor 5 which are distributed on two sides of the heating resistor 4, wherein the heating resistor 4, the first thermistor 3 and the second thermistor 5 are arranged in a silicon dioxide material, and are integrally suspended above a cavity 6; the gas/humidity sensor area comprises an electrode structure 7 of the gas/humidity sensor made of an underlying metal placed in a silicon dioxide material above the heating resistor 4 and a sensitive film material 8 filled or deposited on the electrode structure 7 of the gas/humidity sensor.
The material of the substrate is a silicon wafer.
The material of the structural layer is silicon dioxide.
The heating resistor of the flow sensor and the materials of the first and second thermistors are polysilicon.
The material of the gas/humidity sensing structure is metallic aluminum and a sensitive film material filled or deposited thereon.
See fig. 2: the invention also provides a preparation method of the CMOS MEMS integrated flow and gas/humidity sensor, and FIG. 2 is a preparation flow chart of the CMOS MEMS integrated flow and gas/humidity sensor in the embodiment of the invention, comprising the following steps:
step 1: designing a CMOS bare chip by adopting a 0.18um 1P6M process, designing a reasonable metal layer pattern and metal via in a PAD area, and filling silicon dioxide materials between the two metal layers at the top, so that a natural mask of the PAD area is formed during metal etching to protect the structure of the CMOS bare chip; the method comprises the steps that a reasonable polysilicon layer pattern is designed in a gas flow sensor area to form a heating resistor, a first thermistor and a second thermistor of a flow sensor; a reasonable metal layer pattern and metal via are designed in the flow sensor area, so that a layer of thin silicon dioxide material is reserved above the heating resistor, the first thermistor and the second thermistor to form natural masks of the heating resistor, the first thermistor and the second thermistor, and the via is directly connected with the silicon substrate to form a channel for subsequent silicon etching; and forming an electrode structure of the gas/humidity sensor by utilizing a metal layer pattern and metal via which are reasonably designed on the heating resistor of the flow sensor by using bottom metal. For example: an interdigital capacitive humidity sensing structure is designed.
Step 2: siO for CMOS die in step 1 using ion reactive etching (RIE) 2 Etching to form grooves and microcavities, and exposing the sixth layer of metal aluminum and the substrate silicon. For example: using CF 4 And SF (sulfur hexafluoride) 6 And performing anisotropic dry etching.
Step 3: and (3) carrying out metal aluminum etching on the chip obtained in the step (2) to remove the top metal aluminum. For example: using Cl 2 And BCl 3 And performing anisotropic dry etching.
Step 4: siO is carried out on the chip obtained in the step 3 by adopting ion reactive etching (RIE) 2 Etching to remove SiO on the surface layer 2 And exposes the electrode structure of the gas/humidity sensor above the central heating resistor. For example: using CF 4 And SF (sulfur hexafluoride) 6 And performing anisotropic dry etching.
Step 5: deep Reactive Ion Etching (DRIE) of the chip obtained in step 4 to etch silicon, the above mentioned SiO 2 And forming a silicon trench with high aspect ratio by using the metal layer as a mask of silicon, wherein DRIE (deep reactive ion etching) is also called as a fluorine-based gas-based high aspect ratio silicon dry etching process. For example: SF in HSE200S (deep silicon etcher) 6 And C 4 F 8 Etching and passivating treatment are respectively carried out.
Step 6: xeF is carried out on the chip obtained in the step 5 2 And isotropically dry etching to release the sensor suspension structure. Using XeF 2 The gas is subjected to dry isotropic etching, and etching can be performed on both sides and the bottom of the silicon groove at the same time, so that a heating resistor and a suspension structure of two thermistors are formed.
Step 7: and (3) filling or depositing the sensitive film material on the chip obtained in the step (6) to fill or deposit the sensitive film material on the electrode structure of the gas/humidity sensor. For example: the polyimide was filled onto the electrode structure by dispensing and cured at 150 c for 3 hours.
The practical application of the CMOS MEMS integrated flow and gas/humidity sensor provided by the invention can comprise: attaching the sensor to a carrier (such as a PCB), leading out a wire, connecting the wire with an external signal processing module, and detecting the flow and the gas/humidity in the environment.
The invention fully utilizes the heat of the heating resistor to activate the sensitive film material of the gas/humidity sensor, improves the energy utilization rate, and can reach higher temperature by accurately designing the parameters of the heating resistor of the flow sensor, thereby not only improving the performance of the flow sensor, but also simultaneously improving the sensing efficiency of the gas sensor, and greatly reducing the sensing hysteresis of the humidity sensor using polyimide as the humidity sensitive material; in addition, by designing parameters of the heating resistor to achieve proper response time and using square wave voltage signals with frequency higher than the response frequency of the heating resistor to supply power, the power consumption of the sensor can be greatly reduced and hysteresis of gas/humidity detection can be reduced.
The invention adopts a 0.18um 1P6M CMOS semiconductor technology to design the structure required by the sensor at one time, and comprises a silicon substrate layer 1, a silicon dioxide structure layer 2 and various functional components contained in the silicon dioxide structure layer, and then the CMOS-MEMS monolithic integrated flow and gas/humidity sensor with a suspension structure is obtained through a post-CMOS technology without a mask. Unlike common CMOS-MEMS flow sensor or gas/humidity sensor, the invention provides a preparation method of a single-chip flow and gas/humidity integrated sensor. The gas/humidity and flow rate are measured simultaneously by arranging the gas/humidity sensing structure on the central heating resistor of the flow sensor. The metal layer pattern is designed to become a mask for silicon dioxide and polysilicon, so that a heater, a temperature sensing area and a gas/humidity detection structure of the sensing device can be etched nondestructively without a mask plate, and complex photolithography steps are avoided. Unlike conventional flow sensors, the present invention employs a DRIE anisotropic silicon etching method and XeF 2 The isotropic silicon etching method forms the thermal flow sensor using the suspension structure, and has the advantages of low heat dissipation and high response speed.
The CMOS-MEMS monolithic integrated flow, gas/humidity sensor design and processing method provided by the invention realizes the integration of a single-chip multifunctional sensor, and the integrated design and the subsequent simple processing technology reduce the cost of the sensor; the invention greatly improves the utilization ratio of energy, has the advantages of high stability, high sensitivity, low heat dissipation and low hysteresis, has small volume and high integration level of the single-chip flow and gas/humidity integrated sensor, can effectively solve the problems of large volume and poor suitability caused by simple stacking of the prior single-function sensor, and has the advantages of low energy utilization ratio, high cost, larger heat dissipation, relatively limited sensitivity and response speed of the gas flow and gas/humidity sensor in the market, and has low cost, simple preparation and processing mode and convenient mass production.
The foregoing description of the preferred embodiment of the present invention is not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Other structures and principles are the same as in the prior art and will not be described in detail here.
Claims (2)
1. A CMOS MEMS integrated flow, gas/humidity sensor characterized by: comprises a silicon substrate layer (1) and a silicon dioxide structure layer (2); the silicon dioxide structure layer (2) is arranged above the silicon substrate layer (1); the silicon dioxide structure layer (2) comprises PAD areas arranged at two ends, a gas flow sensor area and a gas humidity sensor area which are arranged in the center; the silicon dioxide material and the metal material in the PAD area are overlapped and distributed, and the metal via penetrates through other metal layers except the top metal layer; the gas flow sensor area comprises a heating resistor (4), a first thermistor (3) and a second thermistor (5) which are distributed on two sides of the heating resistor (4), wherein the heating resistor (4), the first thermistor (3) and the second thermistor (5) are arranged in a silicon dioxide material, and are integrally suspended above the cavity (6); the gas/humidity sensor region includes a heating resistor disposed in a silicon dioxide material and a gas/humidity sensing electrode comprised of a bottommost metal disposed over the heating resistor and a sensitive film material filled or deposited on the gas/humidity sensing electrode.
2. A manufacturing method of a CMOS MEMS integrated flow and gas/humidity sensor is characterized by comprising the following steps of: a Post-CMOS method without mask operation is adopted, and the method comprises the following steps:
step 1: CMOS die: arranging a metal layer pattern and a metal via in the PAD area, and filling silicon dioxide material between the two top layers of metal so as to form a natural mask of the PAD area during metal etching; a polysilicon layer pattern is arranged in the gas flow sensor area to form a heating resistor, a first thermistor and a second thermistor of the flow sensor; a metal layer pattern and metal via are arranged in the gas flow sensor area, so that a layer of thin silicon dioxide material is reserved above the heating resistor, the first thermistor and the second thermistor to form natural masks of the heating resistor, the first thermistor and the second thermistor, and the via is directly connected with the silicon substrate to form a channel for subsequent silicon etching; arranging a metal layer pattern and a metal via above a heating resistor of the gas flow sensor by using bottom metal to form an electrode structure of the gas/humidity sensor;
step 2: siO for CMOS die in step 1 Using RIE 2 Etching to form a groove and a microcavity, so that the top-layer metal aluminum and the substrate silicon are exposed;
step 3: carrying out metal aluminum etching on the chip obtained in the step 2, and removing the top metal aluminum;
step 4: siO is carried out on the chip obtained in the step 3 by adopting RIE 2 Etching to remove SiO on the surface layer 2 And exposing an electrode structure of the gas/humidity sensor above the central heating resistor;
step 5: performing DRIE silicon etching and SiO on the chip obtained in the step 4 2 And forming a silicon trench with a high aspect ratio by using the metal layer as a mask of silicon;
step 6: xeF is carried out on the chip obtained in the step 5 2 Isotropically dry etching to release the sensor suspension structure;
step 7: and (3) filling or depositing the sensitive film material on the chip obtained in the step (6) to fill or deposit the sensitive film material on the electrode structure of the gas/humidity sensor.
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