CN118026086A - CMOS MEMS bimodal gas pressure sensor and preparation method thereof - Google Patents
CMOS MEMS bimodal gas pressure sensor and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a CMOS MEMS bimodal gas pressure sensor and a manufacturing method thereof, belonging to the field of sensors. A bimodal gas pressure sensor comprising a silicon substrate layer and a silicon dioxide structural layer; the silicon dioxide structure layer is arranged above the silicon substrate layer; the silicon dioxide structure layer comprises a confinement region and a capacitive and piezoresistive dual-mode pressure sensing structure arranged in the center. The invention realizes the accurate detection of high linearity compatible with high pressure and low pressure through the piezoresistive and capacitive bimodal detection, and can simultaneously realize the accurate detection of low pressure and high pressure by utilizing the pressure sensing advantages of the piezoresistive and capacitive pressure sensors, thereby increasing the air pressure detection range of the sensor. The invention also discloses a manufacturing method of the dual-mode gas pressure sensor, which utilizes the CMOS technology to manufacture two pressure sensing structures of capacitance type and piezoresistance type in the vertical direction of the same sensor, and the manufacturing method of the invention does not need a Post-CMOS technology of mask, thereby avoiding complex photoetching steps.
Description
Technical Field
The invention relates to a CMOS MEMS bimodal gas pressure sensor and a manufacturing method thereof, in particular to a CMOS MEMS bimodal gas pressure sensor and a manufacturing method thereof, belonging to the field of sensors.
Background
Gas pressure is an important physical quantity and is widely measured in various research fields. Micro pressure sensors are mostly manufactured by adopting MEMS technology, and sense, measure and transmit information in the form of electric signals. By using pressure sensors, different types of pressures can be measured, such as absolute pressure, vacuum pressure, gauge pressure, and differential pressure. MEMS technology for manufacturing pressure sensors is mature, occupies a large part of the sensor market, and is widely applied to industrial production, automobile manufacturing, aerospace, wearable devices, medical appliances and other production and living scenes.
With recent advances in micromachining and MEMS technology, pressure sensors successfully take advantage of these technologies, tending toward miniaturization, integration, pursuing smaller size, higher performance, lower power consumption.
Pressure sensors can be classified into piezoresistive, capacitive, optical fiber, resonant, and piezoelectric types according to the operating principle. Among them, piezoresistive and capacitive are two of the most common pressure sensing methods at present.
The piezoresistive pressure sensor consists of a piezoresistive diaphragm having a wheatstone bridge structure. With the application of pressure, the diaphragm deflects. For thin diaphragms and small deflections, the resistance varies linearly with applied pressure, and all piezoresistors have the same resistance value. When a supply voltage is applied to one end of the wheatstone bridge, the pressure felt by the film is characterized by detecting the voltage difference between the other two terminals. The piezoresistive pressure sensor has a large pressure detection range, is often used for high-pressure detection of the MPa level, and has extremely high linearity.
The capacitive pressure sensor consists of movable film polar plate with opposite surface, fixed polar plate and sealed cavity between the two polar plates. The thin film polar plate moves towards the fixed polar plate under the action of pressure, and the distance between the thin film polar plate and the fixed polar plate is reduced, so that the capacitance value between the polar plates is changed, and the pressure is detected. The capacitive pressure sensor has extremely high sensitivity and is suitable for small-range pressure measurement in a low pressure range, but the nonlinear output of the traditional capacitive pressure sensor causes difficulty in realizing a large-range pressure detection range.
Although the MEMS technology can adopt a more flexible process processing mode and can select wider materials, the MEMS technology is difficult to directly interconnect with a circuit part, so that the overall size of a test micro-system is limited to a certain extent; the performance of the device is also reduced to some extent due to the parasitic capacitance and other problems. Along with the rapid development of the CMOS semiconductor technology, the mature CMOS processing technology has incomparable advantages in the aspect of realizing the miniaturization of devices, meanwhile, the stability of the performance of the devices can be ensured, the feasibility of mass production is ensured, and the research and development period of products is shortened, so that the gas pressure sensor based on the CMOS technology has become the popular direction of scientific research at present. However, the two performance indexes of linearity and measuring range are always contradictory and difficult to balance in the design of the pressure sensor, and each sensor has a correspondingly limited detection range and a single application scene, for example, a sensor with high linearity and high sensitivity at 0-5 kPa cannot be used for detecting the air pressure of 0-200 kPa, and a sensor with a measuring range of 0-2 bar (0-200 kPa) cannot be used for detecting the pressure of 0-5 kPa. It is necessary to develop a gas pressure sensor having high linearity detection capability of both low pressure and high pressure, being compatible with various measurement scenarios, and having advantages in various performance indexes.
Disclosure of Invention
The invention aims to provide a CMOS MEMS bimodal gas pressure sensor and a manufacturing method thereof, which realize accurate detection of high linearity of high pressure and low pressure (or large range) through piezoresistive and capacitive bimodal detection, are compatible with various different production life application scenes, replace a variable-spacing diaphragm type sensing mechanism of a traditional capacitive pressure sensor, utilize the inherent advantages of the CMOS MEMS technology to integrate piezoresistive and capacitive sensing principles at the same time in the vertical direction, optimize a capacitive sensing module, improve the linearity of capacitive detection, adopt Post-CMOS technology without masks in the Post-processing process, avoid complex photoetching steps and obviously improve the efficiency of Post-processing of the whole Post-CMOS.
The aim of the invention is achieved by the following technical scheme.
The invention discloses a CMOS MEMS bimodal gas pressure sensor, which comprises a silicon substrate layer and a silicon dioxide structure layer. The silicon dioxide structure layer is disposed over the silicon substrate layer. The silicon dioxide structure layer comprises a confinement region arranged at the periphery of the capacitive and piezoresistive dual-mode pressure sensing structure and the capacitive and piezoresistive dual-mode pressure sensing structure arranged at the center, namely the capacitive and piezoresistive dual-mode pressure sensing structure comprises a capacitive pressure sensing structure and a piezoresistive pressure sensing structure. In the capacitive pressure sensing structure, silicon dioxide materials and metal materials are overlapped and distributed, metal via penetrates through other metal layers except a sixth layer of metal and a fifth layer of metal, and the sixth layer of metal is the topmost metal. The piezoresistive pressure sensing structure comprises a silicon pressure-sensitive diaphragm and polysilicon piezoresistors distributed in a high-stress area at the edge of the silicon pressure-sensitive diaphragm, wherein the polysilicon piezoresistors are arranged in a silicon dioxide material. The capacitive pressure sensing structure comprises a silicon dioxide structure layer fixed above the pressure-sensitive diaphragm and a silicon dioxide structure layer suspended on the pressure-sensitive diaphragm and fixed with a sensor edge confinement region, wherein the silicon dioxide structure layer fixed above the pressure-sensitive diaphragm is used as a movable comb tooth, and the silicon dioxide structure layer suspended on the pressure-sensitive diaphragm and fixed with the sensor edge confinement region is used as a fixed comb tooth structure; the silicon dioxide structural layer serving as the comb tooth structure comprises a first layer, a second layer, a third layer, a fourth layer and metal via penetrating through the fourth layer of metal, so that the capacitance pressure sensing structure is formed.
The invention discloses a manufacturing method of a CMOS MEMS bimodal gas pressure sensor, which adopts Post-CMOS process processing without mask, comprising the following steps:
Step 1: manufacturing a CMOS bare chip by adopting a 1P6M process, arranging a confinement region at the periphery by taking a sixth layer metal and a fifth layer metal as confinement layers, and designing a metal layer pattern in a pressure sensing structure region to serve as a hard mask for etching silicon dioxide by using a Post-CMOS process; the first layer to the fourth layer of metal layers and the metal via are adjusted to form comb-tooth capacitors serving as capacitive pressure sensing structures, and electrode leads of the capacitive pressure sensing structures are formed at the same time; a polysilicon layer pattern is adopted as a sacrificial layer for releasing the fixed comb tooth suspension structure; adjusting the first layer metal pattern to enable the first layer metal pattern to be used as a protective layer of the polycrystalline silicon piezoresistor and an electrode lead of the polycrystalline silicon piezoresistor;
Preferably, a 0.18um 1p6m process is used to fabricate the CMOS die.
Step 2: and (3) deep silicon etching on the back of the CMOS bare chip obtained in the step (1) by using a DRIE process to obtain a silicon pressure-sensitive membrane with a capacitive and piezoresistive dual-mode pressure sensing structure, namely obtaining the chip after the step (2) is completed.
Step 3: and (3) carrying out silicon dioxide etching on the chip obtained in the step (2) by using an AOE process until the chip is etched to the polycrystalline silicon sacrificial layer to obtain a capacitive and piezoresistive dual-mode pressure sensing structure, namely a comb tooth capacitive structure for capacitive pressure sensing and a piezoresistor for piezoresistive pressure sensing, and obtaining the chip after the step (3) is completed.
Step 4: and (3) etching and releasing the polysilicon by using XeF 2 on the chip obtained in the step (3), removing the polysilicon layer buried in the oxide layer below the fixed comb tooth structure, and obtaining a fixed comb tooth electrode structure suspended above the pressure-sensitive membrane, thus obtaining the chip after the step (4) is completed.
Step 5: and (3) packaging the chip obtained in the step (4) to prepare the single-chip CMOS MEMS bimodal gas pressure sensor.
The beneficial effects are that:
1. The invention discloses a CMOS MEMS bimodal gas pressure sensor and a manufacturing method thereof, which utilize the advantages of a CMOS process to simultaneously manufacture two pressure sensing structures of capacitance type and piezoresistance type in the vertical direction of the same sensor, thereby realizing bimodal pressure detection.
2. The CMOS MEMS bimodal gas pressure sensor and the manufacturing method thereof can realize accurate detection of low pressure and high pressure simultaneously by using the pressure sensing advantages of the piezoresistive pressure sensor and the capacitive pressure sensor simultaneously through CMOS and MEMS bimodal pressure detection, increase the air pressure detection range of the sensor, ensure linearity in a wide range, realize high linearity and high sensitivity detection in a small range of 0-80 kPa by using a capacitance mode, and realize large-range linear detection of 0-300 kPa by using a piezoresistive mode.
3. The invention discloses a CMOS MEMS bimodal gas pressure sensor and a manufacturing method thereof, which change a variable-spacing diaphragm type sensing mechanism of a traditional capacitive pressure sensor by optimally designing a capacitive sensing structure by utilizing the advantages of a CMOS process, realize a three-dimensional capacitive comb tooth structure by utilizing a metal layer and a metal via between the metal layers, realize pressure detection by the change of the longitudinal overlapping area of the capacitive comb teeth, and greatly improve the linearity of capacitive pressure sensing.
4. The CMOS MEMS bimodal gas pressure sensor and the manufacturing method thereof can realize single-chip bimodal pressure detection, integrate CMOS and MEMS two sensing principles in the vertical direction, realize wide-range, high-precision and high-linearity pressure detection by utilizing the advantages of high sensitivity and large range of the piezoresistive pressure sensor, simultaneously output two different pressure detection signals, be compatible with various application scenes, and have the advantages of good stability, high sensitivity and the like; the CMOS MEMS sensor device has the advantages of small volume, high integration level, convenience for large-scale production, no mask plate in partial Post-CMOS process steps, low cost, simple process steps, convenience for processing and the like.
Drawings
FIG. 1 is a top plan schematic view of a CMOS MEMS bimodal gas pressure sensor of the present invention; wherein: 1-confinement region (composed of fifth and sixth layers of metal); 2-p doped polysilicon varistor (the part of the end that enters region 1 represents it buried in the silicon dioxide structural layer to facilitate the placement of metal electrode leads); a movable comb electrode structure (fixed on the pressure sensitive membrane) of the 3-capacitive pressure sensing structure; 4-silicon pressure sensitive membrane; a fixed comb electrode structure of the 5-capacitance type pressure sensing structure (the bottom is separated from the pressure sensitive membrane, and the beam is fixedly connected with the confinement region);
FIG. 2 is a flow chart of the fabrication of a CMOS MEMS bimodal gas pressure sensor of the present invention; wherein, figure a is a CMOS bare chip designed by using a 0.18um 1P6M process, figure b is a method for carrying out back cavity deep silicon etching on the CMOS bare chip by using a DRIE process, defining a pressure sensitive diaphragm of a pressure sensor, figure c is a method for etching silicon dioxide by using an AOE process, defining a polysilicon piezoresistor and a comb capacitor structure, and figure d is a method for isotropically etching a polysilicon sacrificial layer by XeF 2 to release a fixed comb structure;
FIG. 3 is a cross-sectional view of a CMOS MEMS dual mode gas pressure sensor of the present invention.
Wherein: 1-confinement region (fifth layer and sixth layer of metal); 2-p doped polysilicon varistor (the part of the end that enters region 1 represents it buried in the silicon dioxide structural layer to facilitate the placement of metal electrode leads); a movable comb electrode structure (fixed on the pressure sensitive membrane) of the 3-capacitive pressure sensing structure; 4-silicon pressure sensitive membrane; a fixed comb electrode structure of the 5-capacitance type pressure sensing structure (the bottom is separated from the pressure sensitive membrane, and the beam is fixedly connected with the confinement region); a 6-silicon substrate; 7-silicon dioxide structural layer.
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 embodiment discloses a CMOS MEMS bimodal gas pressure sensor, which comprises a silicon substrate 6 and a silicon dioxide structure layer 7, wherein the silicon dioxide structure layer 7 is arranged above the silicon substrate 6; the silicon dioxide structure layer 7 comprises a capacitive pressure sensing structure and a piezoresistive pressure sensing structure which are arranged in the silicon dioxide structure layer; the capacitive pressure sensing structure consists of a metal layer contained in the silicon dioxide structural layer 7 and metal via penetrating through the metal layer, namely a movable comb electrode structure 3 of the capacitive pressure sensing structure and a fixed comb electrode structure 5 of the capacitive pressure sensing structure; the silicon substrate 6 comprises a silicon pressure sensitive membrane 4; the piezoresistive pressure sensing structure is composed of a silicon pressure-sensitive diaphragm 4 and a p-type doped polysilicon piezoresistor 2 in a silicon dioxide structure layer 7; the confinement region 1 is composed of a fifth layer and a sixth layer of metal.
The material of the silicon substrate 6 is a silicon wafer.
The material of the pressure sensitive membrane is silicon.
The material of the sensor piezoresistor is p-type doped polysilicon.
The materials of the capacitive pressure sensing structure of the sensor are a silicon dioxide structure layer and a metal via contained therein.
See fig. 2: the embodiment also provides a method for manufacturing the CMOS MEMS bimodal gas pressure sensor, and fig. 2 is a flowchart of the CMOS MEMS bimodal gas pressure sensor, which specifically comprises the following steps:
Step 1: designing a CMOS bare chip by adopting a 0.18um 1P6M CMOS process, setting a confinement region at the periphery by using a sixth layer metal and a fifth layer metal as confinement layers, and designing a metal layer pattern at a pressure sensing structure region as a hard mask for etching silicon dioxide by using a Post-CMOS process; the first layer to the fourth layer of metal layer patterns and the metal via are reasonably designed to form comb tooth capacitors as capacitive pressure sensing structures, and electrode leads of the capacitive pressure sensing structures are formed at the same time; the design of the polysilicon layer pattern is reasonable, and the polysilicon layer pattern is used as a sacrificial layer and a protective layer for releasing a fixed comb tooth suspension structure; the first metal pattern is designed reasonably, so that the first metal pattern is used as a protective layer of the polysilicon piezoresistor and an electrode lead of the polysilicon piezoresistor. For example: the size of the designed membrane is 3000um square, and the beams of the fixed comb teeth and the movable comb teeth structure are separated from the piezoresistor by a distance in the edge area of the membrane, so that the influence on the high stress area of the pressure sensitive membrane is reduced.
Step 2: the back side deep silicon etch is performed on the CMOS die obtained in step 1 using a DRIE process, which defines a silicon pressure sensitive diaphragm of a capacitive and piezoresistive dual mode pressure sensing structure. For example: and (3) taking the PI adhesive tape as a mask for back etching of the small chip, respectively carrying out etching and passivation treatment in an HSE200S (deep silicon etching machine) by using SF 6 and C 4F8, and controlling the etching depth to ensure that the pressure-sensitive membrane is defined to be 5-10 um.
Step 3: and (3) performing silicon dioxide etching on the chip obtained in the step (2) by using an AOE process, and defining a pressure sensing structure, wherein the pressure sensing structure comprises a comb tooth capacitance structure of a capacitance type pressure sensing structure and a piezoresistor of piezoresistance type pressure sensing. For example: siO 2 is etched in an STS AOE etcher using CF 4 and SF 6, and the control of etch depth is stopped at the time of the polysilicon sacrificial layer.
Step 4: and (3) etching and releasing the polysilicon by using XeF 2 to the chip obtained in the step (3), removing the polysilicon sacrificial layer buried in the oxide layer below the fixed comb tooth structure, and defining the fixed comb tooth electrode structure of the capacitive pressure sensing structure. For example: the etching rate is controlled to completely remove the polysilicon sacrificial layer.
Step 5: and (3) packaging the chip obtained in the step (4) to prepare the single-chip CMOS MEMS bimodal gas pressure sensor.
The practical application of the CMOS MEMS dual-mode gas pressure sensor provided in this embodiment includes: the sensor is attached to a carrier (such as a PCB board) for airtight packaging, leads are led out, and the sensor is connected with an external signal processing module to detect the gas pressure in various environments such as low pressure, high pressure and the like, for example, the pressure detection of a small range of 0 to 80kPa and the pressure detection of a large range of 0 to 200 kPa.
The embodiment fully utilizes the advantages of a 0.18um 1P6M CMOS process, integrates two sensing mechanisms of piezoresistance and capacitance detection in the vertical direction, and eliminates the detection principle of the traditional diaphragm variable-spacing capacitive pressure sensor, realizes a comb tooth capacitance structure in the three-dimensional vertical direction by utilizing multiple layers of metals and metal via penetrating through metal layers, generates capacitance value change through the change of comb tooth overlapping area, and greatly improves the linearity of detection capacitance signals by the capacitance sensing principle; meanwhile, the piezoresistor is designed by utilizing the polysilicon layer and the sacrificial layer for releasing the suspension structure is used for realizing the piezoresistor sensing principle, and meanwhile, the pressure detection with wide range and high linearity is satisfied, so that the piezoresistor is suitable for various application scenes.
The embodiment adopts a structure required by a 0.18um 1P6M CMOS semiconductor process for designing the sensor at one time, comprises a silicon substrate layer, a silicon dioxide structure layer and various functional components contained in the silicon dioxide structure layer, and then the CMOS-MEMS dual-mode gas pressure sensor with a suspension structure is obtained through a post-CMOS process which is partially free of a mask plate, and the process steps are simple. Unlike common CMOS-MEMS gas pressure sensor, the invention provides a preparation method of a gas pressure sensor for realizing piezoresistance and capacitance bimodal detection by a single chip.
The manufacturing method of the CMOS-MEMS single-bimodal gas pressure sensor provided by the embodiment can integrate multiple sensing detection principles of a single chip, and the cost of the sensor is reduced due to the integrated design and the subsequent simple processing technology; the embodiment can greatly improve the linearity of pressure detection, has the advantage of simultaneously realizing wide-range and high-linearity detection, has small volume and strong compatibility, and is easy to be matched with a CMOS circuit.
The foregoing description of the preferred embodiments of the application is not intended to be limiting, but rather is intended to cover all modifications, equivalents, alternatives, and improvements that fall within the spirit and scope of the application. Other structures and principles are the same as in the prior art and will not be described in detail here.
Claims (3)
1. A CMOS MEMS bimodal gas pressure sensor characterized by: comprises a silicon substrate layer and a silicon dioxide structure layer; the silicon dioxide structure layer is arranged above the silicon substrate layer; the silicon dioxide structure layer comprises a confinement region arranged at the periphery of the capacitive and piezoresistive dual-mode pressure sensing structure and a capacitive and piezoresistive dual-mode pressure sensing structure arranged at the center, namely the capacitive and piezoresistive dual-mode pressure sensing structure comprises a capacitive pressure sensing structure and a piezoresistive pressure sensing structure; the silicon dioxide material and the metal material in the capacitive pressure sensing structure are overlapped and distributed, the metal via penetrates through other metal layers except a sixth layer metal and a fifth layer metal, and the sixth layer metal is the topmost metal; the piezoresistive pressure sensing structure comprises a silicon pressure-sensitive diaphragm and polysilicon piezoresistors distributed in a high-stress area at the edge of the silicon pressure-sensitive diaphragm, wherein the polysilicon piezoresistors are arranged in a silicon dioxide material; the capacitive pressure sensing structure comprises a silicon dioxide structure layer fixed above the pressure-sensitive diaphragm and a silicon dioxide structure layer suspended on the pressure-sensitive diaphragm and fixed with a sensor edge confinement region, wherein the silicon dioxide structure layer fixed above the pressure-sensitive diaphragm is used as a movable comb tooth, and the silicon dioxide structure layer suspended on the pressure-sensitive diaphragm and fixed with the sensor edge confinement region is used as a fixed comb tooth structure; the silicon dioxide structural layer serving as the comb tooth structure comprises a first layer, a second layer, a third layer, a fourth layer and metal via penetrating through the fourth layer of metal, so that the capacitance pressure sensing structure is formed.
2. A CMOS MEMS bimodal gas pressure sensor as claimed in claim 1, wherein: the manufacturing method adopts Post-CMOS process without mask, and comprises the following steps,
Step 1: manufacturing a CMOS bare chip by adopting a 1P6M process, arranging a confinement region at the periphery by taking a fifth layer of metal and a sixth layer of metal as confinement layers, and designing a metal layer pattern in a pressure sensing structure region to serve as a hard mask for etching silicon dioxide by using a Post-CMOS process; the first layer to the fourth layer of metal layers and the metal via are adjusted to form comb-tooth capacitors serving as capacitive pressure sensing structures, and electrode leads of the capacitive pressure sensing structures are formed at the same time; a polysilicon layer pattern is adopted as a sacrificial layer for releasing the fixed comb tooth suspension structure; adjusting the first layer metal pattern to enable the first layer metal pattern to be used as a protective layer of the polycrystalline silicon piezoresistor and an electrode lead of the polycrystalline silicon piezoresistor;
step 2: deep silicon etching is carried out on the back of the CMOS bare chip obtained in the step 1 by using a DRIE process, so that a silicon pressure-sensitive membrane with a capacitive and piezoresistive dual-mode pressure sensing structure is obtained, and a chip after the step 2 is completed is obtained;
Step 3: carrying out silicon dioxide etching on the chip obtained in the step 2 by using an AOE process until the chip is etched to a polycrystalline silicon sacrificial layer to obtain a capacitive and piezoresistive dual-mode pressure sensing structure, wherein the capacitive and piezoresistive dual-mode pressure sensing structure comprises a comb tooth capacitive structure for capacitive pressure sensing and a piezoresistor of the piezoresistive pressure sensing structure, and the chip after the step3 is completed is obtained;
step 4: etching and releasing the polysilicon of the chip obtained in the step 3 by using XeF 2, removing the polysilicon layer buried in the oxide layer below the fixed comb tooth structure to obtain a fixed comb tooth electrode structure suspended above the pressure sensitive membrane, and obtaining the chip after the step 4 is completed;
Step 5: and (3) packaging the chip obtained in the step (4) to prepare the single-chip CMOS MEMS bimodal gas pressure sensor.
3. A CMOS MEMS bimodal gas pressure sensor as claimed in claim 2, wherein: CMOS die were fabricated using a 0.18um 1p6m process.
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