A method for manufacturing a MEMS four-in-one monolithic integrated sensor

Abstract

The application provides a manufacturing method of a MEMS four-in-one monolithic integrated sensor. The four-in-one monolithic integrated sensor integrates multiple sensor functions on a single silicon wafer, can measure pressure, acceleration, gas and humidity at the same time, and can be used for multi-parameter synchronous detection in a complex scene. The four-in-one integrated sensor is manufactured by using a surface micromachining process. In order to form the cavity structures required by the pressure sensor, the acceleration sensor, the gas sensor and the humidity sensor, the method of filling SiO2 and etching polysilicon by using an HF solution to release the cavity is used. In this way, not only the process compatibility of various functional sensors is beneficial, but also the yield of the integrated sensor can be improved. Meanwhile, the manufacturing cost of the integrated sensor is relatively low, and the integrated sensor is suitable for mass production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor devices, in particular to a manufacturing method of a MEMS four-in-one monolithic integrated sensor. BACKGROUND

[0002] As a relatively mature semiconductor technology, MEMS (Micro Electro Mechanical System) has been widely used in various fields, for example, sensors made by MEMS technology can be applied to smart home appliances, emergency rescue, public safety, robots, etc.

[0003] Taking a seismic search and rescue unmanned aerial vehicle as an example, in order to ensure that its functions and navigation system can normally operate in a dangerous and complex environment, an accelerometer, a gyroscope, an air pressure sensor, an ultrasonic sensor, etc. need to be installed on the unmanned aerial vehicle, so that the unmanned aerial vehicle can maximize its effect. Since sensors are often used in complex environments, a single-function sensor cannot measure multiple types of physical quantities at the same time, and the installation of multiple-function sensors will occupy a large area and consume a lot of power, which cannot meet the actual demand, so the development trend of future MEMS sensors mainly focuses on miniaturization, multifunctionalization and integration.

[0004] The number of sensors integrated by the traditional integrated sensor is small, so the corresponding function is also small, and most of them use bulk silicon micromachining technology, which has low device yield and high manufacturing cost.

[0005] Therefore, a new integrated sensor is needed to integrate more types of sensors and improve yield and reduce manufacturing cost. SUMMARY

[0006] The purpose of the present application is to provide a manufacturing method of a MEMS four-in-one monolithic integrated sensor, which integrates the functions of pressure, acceleration, gas and humidity sensors, improves work efficiency and yield.

[0007] In order to achieve the above purpose, the present application provides a manufacturing method of a MEMS four-in-one monolithic integrated sensor for the integration of acceleration sensors, pressure sensors, gas sensors and humidity sensors, comprising:

[0008] S1: providing a silicon wafer, depositing an isolation layer on the silicon wafer;

[0009] S2: using SiO2 to respectively manufacture a boss of each of the acceleration, pressure, gas and humidity sensors and an etching pin adjacent to each boss on the isolation layer as a sacrificial layer, thereby obtaining a silicon wafer with a sacrificial layer;

[0010] S3: depositing a low-stress silicon nitride layer on the entire silicon wafer with the sacrificial layer as a structure layer and a sensitive diaphragm.

[0011] S4: fabricate a sensitive device on the sensitive diaphragm, which changes based on the deformation of the sensitive diaphragm, and which includes sensitive resistors required by acceleration and pressure sensors; and fabricate a test electrode of a gas sensor and a test electrode of a humidity sensor on the sensitive diaphragm;

[0012] S5: etch the sensitive diaphragm above the etching pins to obtain etching release holes penetrating through the sensitive diaphragm;

[0013] S6: place the silicon wafer in a solution of about 3% ~ 7% HF, so that the HF solution etches the sacrificial layer through the etching release holes, and at the same time, observe the color change of the boss under the sensitive diaphragm for multiple times, and stop etching when the color of the boss is observed to change completely;

[0014] S7: deposit a multi-layer material formed by an alternating stack of silicon nitride and silicon dioxide at the etching release holes to obtain a plugging layer to plug all the etching release holes;

[0015] S8: respectively coat a gas sensitive material of a gas sensor and a sensitive material of a humidity sensor on the test electrode of the gas sensor and the test electrode of the humidity sensor to obtain a MEMS four-in-one monolithic integrated sensor.

[0016] The step S2 specifically comprises:

[0017] S21: deposit SiO2 on the isolation layer, and perform photolithography and etching to patternize it and form bosses of acceleration, pressure, gas, and humidity sensors respectively at positions corresponding to the acceleration, pressure, gas, and humidity sensors;

[0018] S22: again deposit a layer of SiO2 on the isolation layer, and perform photolithography and etching to patternize it and form etching pins adjacent to the respective bosses.

[0019] The step S4 specifically comprises:

[0020] S41: deposit a layer of low-stress polysilicon on the sensitive diaphragm, perform boron ion implantation annealing, and then perform photolithography and etching to patternize the polysilicon to form sensitive resistors of acceleration and pressure sensors respectively at positions corresponding to the sensitive resistors of the acceleration and pressure sensors;

[0021] S42: deposit a layer of low-stress silicon nitride at the sensitive resistors of the acceleration and pressure sensors as a protective layer of the sensitive resistors of the acceleration and pressure sensors;

[0022] S43: fabricate electrode leads on the sensitive resistors of the acceleration sensor and the pressure sensor respectively;

[0023] S44: fabricating test electrodes of the gas sensor and the humidity sensor on the sensitive membrane sheet at the gas sensor and the humidity sensor respectively.

[0024] The step S43 specifically comprises: etching the protective layer of the sensitive resistor of the acceleration sensor and the pressure sensor respectively to form lead holes of the sensitive resistor of the acceleration sensor and the pressure sensor, and sputtering a layer of gold as electrode lead at the lead holes.

[0025] The step S4 further comprises: step S45: fabricating a mass block on the sensitive membrane sheet at the acceleration sensor, the mass block being made of copper and having a thickness within 10 μm.

[0026] In the step S41, the thickness of the sensitive resistor is about 4000 Å ~ 4500 Å, the ion implantation energy of the implantation annealing is 60 KeV, the implantation dose is 5×10 15 ions / cm 2 , the annealing temperature is 1000 degrees Celsius, and the annealing is performed in nitrogen; in the step S42, the thickness of the protective layer of the sensitive resistor is about 1400 Å ~ 2000 Å; and in the step S43, the thickness of the electrode lead is about 3000 Å ~ 4000 Å.

[0027] In the step S7, the obturation layer is obtained by: using PECVD to deposit silicon nitride, silicon dioxide, and silicon nitride to obtain a multi-layer material in the form of silicon nitride-silicon dioxide-silicon nitride, and performing photolithography and etching to pattern the multi-layer material, so as to obtain the obturation layer.

[0028] The silicon wafer is a single-polished N+ type <100> silicon wafer; the isolation layer is low-stress silicon nitride, and has a thickness of 2000 Å ~ 5000 Å; the thickness of the boss is 8000 Å ~ 20000 Å, and the thickness of the etched pin is 2000 Å ~ 4000 Å.

[0029] The gas-sensitive material of the gas sensor is SnO2 / TiO2, the humidity-sensitive material of the humidity sensor is ZnO / PEG, and the gas-sensitive material of the gas sensor and the humidity-sensitive material of the humidity sensor are applied on the test electrodes of the gas sensor and the humidity sensor by a spotting method.

[0030] In another aspect, the application provides a MEMS four-in-one monolithic integrated sensor, which is fabricated based on the fabrication method of the MEMS four-in-one monolithic integrated sensor described above.

[0031] The manufacturing method of the MEMS four-in-one monolithic integrated sensor of the present application firstly manufactures the cavities of the gas and humidity sensors on the surface of a silicon wafer, and can manufacture an integrated sensor which integrates the functions of four sensors of pressure, acceleration, gas and humidity, each of which can work normally and has a certain level of performance, and thus can be used in complex scenes and detect four kinds of physical quantities simultaneously, thereby improving the work efficiency; in addition, the four-in-one monolithic integrated sensor is manufactured by using the surface silicon micromachining technology, has a high yield and low manufacturing cost, and can be mass-produced.

[0032] In addition, the manufacturing method of the MEMS sensor of the present application adopts the plugging method of filling the etching holes with multiple layers of materials, the molecular structures of the multiple layers of materials are staggered with each other, which can improve the compactness and further improve the air tightness, so that the stability of the device performance can be maintained for a longer time. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a flow chart of the manufacturing method of the MEMS four-in-one monolithic integrated sensor of the present application;

[0034] Figures 2A-2I is a cross-sectional schematic view of the silicon wafer and the components thereon at each step of the manufacturing method of the MEMS four-in-one monolithic integrated sensor of the present application.

[0035] Figure 3 is a schematic view of the sensor size and position of the MEMS four-in-one monolithic integrated sensor of the present application.

[0036] Figure 4A is a photo of the MEMS four-in-one monolithic integrated sensor of the present application, in which the left half of the figure is a microscope photo of the MEMS four-in-one monolithic integrated sensor of the present application, and the right half of the figure is a comparison photo with a 1 corner coin.

[0037] Figure 4B is a response result graph of the pressure sensor of the MEMS four-in-one monolithic integrated sensor of the present application.

[0038] Figure 4C is a response result graph of the acceleration sensor of the MEMS four-in-one monolithic integrated sensor of the present application.

[0039] Figure 4D is a response result graph of the gas sensor of the MEMS four-in-one monolithic integrated sensor of the present application.

[0040] Figure 4E is a response result graph of the humidity sensor of the MEMS four-in-one monolithic integrated sensor of the present application. DETAILED DESCRIPTION

[0041] The application will be further described in conjunction with specific embodiments. It should be understood that the following embodiments are only used to illustrate the application but not to limit the scope of the application.

[0042] As Figure 1 shown is a flow chart of a manufacturing method of a MEMS four-in-one monolithic integrated sensor according to an embodiment of the application, which can be applied to synchronous detection of multiple physical quantities in complex scenes, such as emergency rescue, public safety and environmental detection scenes, which need to acquire multiple physical quantities at the same time, thereby improving operation efficiency.

[0043] The manufacturing method of the MEMS four-in-one monolithic integrated sensor of the application is used for integration of an acceleration sensor 10, a pressure sensor 20, a gas sensor 30 and a humidity sensor 40, which comprises the following steps:

[0044] Step S1: as shown in the figure, a silicon wafer 100 is provided, and a separation layer 200 is deposited on the silicon wafer 100. Figure 2A

[0045] In the embodiment, the deposition adopts an LPCVD process. The silicon wafer 100 is a single-polished N+ type <100> silicon wafer, and the separation layer 200 is low-stress silicon nitride, with a thickness of 4000 Å ~ 5000 Å. In other embodiments, the material of the separation layer can be selected and the thickness can be adjusted within the range of 2000 Å ~ 5000 Å.

[0046] Step S2: using SiO2, the acceleration, pressure, gas and humidity sensors are respectively manufactured on the separation layer 200 to obtain respective bosses and etching pins adjacent to the respective bosses, as a sacrificial layer, thereby obtaining a silicon wafer with a sacrificial layer;

[0047] That is, the bosses include a first boss 301 corresponding to the acceleration sensor, a second boss 302 corresponding to the pressure sensor, a third boss 303 corresponding to the gas sensor, and a fourth boss 304 corresponding to the humidity sensor. The first boss 301, the second boss 302, the third boss 303 and the fourth boss 304 are respectively adjacent to the first etching pin 305, the second etching pin 306, the third etching pin 307 and the fourth etching pin 308.

[0048] Among them, the sacrificial layer is used as a filler for forming the bosses and the etching pins so as to be released subsequently; the bosses are used to become vacuum cavities after being released, so that the sensitive diaphragm can be deformed when external load is applied to the sensitive diaphragm; the etching pins are used as a "fuse" when the bosses are released, for guiding the etching solution and accelerating the etching speed.

[0049] The step S2 specifically comprises:

[0050] ​Step S21: As Figure 2B As shown, SiO2 is deposited on the isolation layer, and photolithography and etching are performed on it (i.e., the deposited polycrystalline silicon) to pattern it and form the respective bosses of the acceleration, pressure, gas, and humidity sensors at the positions corresponding to the acceleration, pressure, gas, and humidity sensors.

[0051] In this embodiment, the deposition is performed using an LPCVD process. In this embodiment, the thickness of the boss is 20,000 Å; in other embodiments, the thickness is adjustable within the range of 8,000 Å to 20,000 Å.

[0052] Step S22: As Figure 2C As shown, another layer of SiO2 is deposited on the isolation layer, and then photolithographically and etched to pattern it and form etched pins adjacent to the respective bosses.

[0053] In this embodiment, the deposition is performed using an LPCVD process. The thickness of the etched pin is 2000 Å, and in other embodiments, the thickness is adjustable within the range of 2000 Å to 4000 Å.

[0054] Step S3: As Figure 2D As shown, a low-stress silicon nitride layer is deposited on the entire silicon wafer with a sacrificial layer as a structural layer and a sensitive film 400.

[0055] Low-stress silicon nitride serves as both a structural layer for devices and a sensitive film.

[0056] In this embodiment, the deposition is performed using an LPCVD process. The thickness of the sensitive film 400 is 12000 Å, and in other embodiments, its thickness is adjustable within the range of 8000 Å to 12000 Å.

[0057] Step S4: As Figure 2E As shown, a sensitive device that changes based on the deformation of the sensitive diaphragm is fabricated on the sensitive diaphragm 400. The sensitive device includes a sensitive resistor 500 required for acceleration and pressure sensors. Furthermore, a test electrode 601 for a gas sensor and a test electrode 701 for a humidity sensor are fabricated on the sensitive diaphragm 400.

[0058] In this embodiment, as Figure 2E As shown, the sensitive resistor 500 of the acceleration and pressure sensor is a polycrystalline silicon resistor, and step S4 specifically includes:

[0059] Step S41: depositing a low-stress polysilicon layer on the sensitive diaphragm 400, boron ion implantation annealing, then photoetching and etching the polysilicon to pattern the sensitive diaphragm 400 to form the sensitive resistors 500 of the acceleration and pressure sensors respectively at positions corresponding to the sensitive resistors of the acceleration and pressure sensors;

[0060] Thus, the sensitive resistor 500 serves as a piezoresistor of the acceleration sensor and a piezoresistor of the pressure sensor, and forms a Wheatstone bridge to output the change in an electrical quantity.

[0061] In the step S41, the deposition is performed by using the LPCVD process. The thickness of the sensitive resistor is 4000 A, and in other embodiments, the thickness can be adjusted. The shape of the sensitive resistor after photoetching is a serpentine resistor strip. The ion implantation energy of the implantation annealing is 60 KeV, the implantation dose is 5x1015 ions / cm2, the annealing temperature is 1000 degrees Celsius, and nitrogen is used. 15 ions / cm2 2

[0062] Step S42: depositing a low-stress silicon nitride layer on the sensitive resistors 500 of the acceleration and pressure sensors as a protective layer 501 of the sensitive resistors of the acceleration and pressure sensors.

[0063] The deposition is performed by using the LPCVD process. In this embodiment, the thickness of the protective layer of the sensitive resistor 500 is 2000 A, and in other embodiments, the thickness can be adjusted.

[0064] Step S43: fabricating electrode leads 502 on the sensitive resistors 500 of the acceleration and pressure sensors respectively, which specifically includes:

[0065] Etching the protective layer of the sensitive resistor of the acceleration and pressure sensors respectively to form lead holes of the sensitive resistors of the acceleration and pressure sensors, and sputtering a layer of gold as the electrode leads 502 at the lead holes.

[0066] In this embodiment, the thickness of the electrode leads 502 is 3000 A ~ 4000 A, and in other embodiments, the depth can be adjusted. The electrode leads 502 are formed by the lift-off process.

[0067] Step S44: fabricating test electrodes 601, 701 of the gas sensor and the humidity sensor respectively on the sensitive diaphragm 400 at the gas sensor and the humidity sensor.

[0068] In this embodiment, the thickness of the test electrode 601 of the gas sensor and the test electrode 701 of the humidity sensor is 3000 A, and in other embodiments, the thickness can be adjusted.

[0069] ​In some embodiments, a heating electrode is provided between the test electrode 601 of the gas sensor and the sensitive diaphragm 400 at the gas sensor, and the heating electrode is spaced apart from the test electrode 601 by an insulating layer. The material of the insulating layer is preferably silicon dioxide. Accordingly, in the step S44, the test electrode 601 of the gas sensor is specifically fabricated by sequentially sputtering a heating electrode, depositing an insulating layer, and sputtering a test electrode on the sensitive diaphragm 400 at the gas sensor.

[0070] Step S45: As shown in Figure 2F , a mass 503 is fabricated on the sensitive diaphragm 400 at the acceleration sensor to increase the sensitivity.

[0071] The mass 503 is deposited by electroplating. In this embodiment, the mass 503 is made of copper, and the thickness of the mass 503 is 6 μm, which is verified by a slice. In other embodiments, the thickness of the mass 503 can be within 10 μm.

[0072] In some embodiments, the fabrication step of the mass 503 can be omitted, and the sensitivity is relatively low.

[0073] Step S5: As shown in Figure 2G , the sensitive diaphragm 400 above the etching pin is etched to obtain an etching release hole 401 penetrating through the sensitive diaphragm 400;

[0074] Thus, the etching release hole of the acceleration, pressure, gas, and humidity sensor is obtained.

[0075] Step S6: As shown in Figure 2H , the silicon slice is placed in an HF solution to etch the sacrifice layer through the etching release hole 401 (note: the position other than the etching release hole is covered by PECVD SiN), and the color of the boss under the sensitive diaphragm 400 is observed multiple times to determine whether the color changes, and the etching is stopped when the color of the boss changes completely.

[0076] At this point, the cavity structure is formed. After the etching is stopped, the silicon slice can be cleaned and dried at 120 °C.

[0077] The boss under the sensitive diaphragm 400 is originally grayish brown, and becomes colored after the color changes. When the color changes completely, it means that all the polysilicon is etched completely.

[0078] Step S7: As shown in Figure 2I , a silicon nitride-silicon dioxide-silicon nitride multilayer material is deposited at the etching release hole to obtain a plugging layer 402 to plug all the etching release holes.

[0079] The multi-layer material stack can improve the density and thus the air tightness of the cavity. In addition, the multi-layer material can also be silicon dioxide-silicon nitride-silicon dioxide, as long as the multi-layer material is formed by stacking silicon nitride and silicon dioxide alternately.

[0080] The obturation layer is obtained by depositing silicon nitride, silicon dioxide, and silicon nitride by PECVD to obtain a silicon nitride-silicon dioxide-silicon nitride multi-layer material, and performing photolithography and etching to pattern the multi-layer material, thereby obtaining the obturation layer.

[0081] The thicknesses of the silicon nitride, silicon dioxide, and silicon nitride of the silicon nitride-silicon dioxide-silicon nitride multi-layer material are 6000 Å, 4000 Å, and 6000 Å, respectively, and in other embodiments, the thicknesses can be adjusted as long as the obturation layer can completely obturate the release hole, i.e., the deposition thickness of the obturation layer is higher than the depth of the etching release hole.

[0082] Step S8: coating a gas-sensitive material of the gas sensor and a humidity-sensitive material of the humidity sensor on the test electrodes 601 and 701 of the gas sensor and the humidity sensor, respectively, to obtain a MEMS four-in-one monolithic integrated sensor. The obtained MEMS four-in-one monolithic integrated sensor integrates the acceleration sensor 10, the pressure sensor 20, the gas sensor 30, and the humidity sensor 40.

[0083] The gas-sensitive material of the gas sensor is SnO2 / TiO2, and the humidity-sensitive material of the humidity sensor is ZnO / PEG. The sensitive materials of the gas and humidity sensors are coated on the test electrodes of the gas and humidity sensors by spotting to obtain the four-in-one monolithic integrated sensor.

[0084] At this point, the entire four-in-one monolithic integrated sensor process is completed. Thus, the four-in-one monolithic integrated sensor obtained based on the four-in-one monolithic integrated sensor manufacturing method described above integrates the four sensors of the pressure sensor, the acceleration sensor, the gas sensor, and the humidity sensor. The layout and size of the four sensors are as shown in FIG. 1. Figure 3 The four-in-one monolithic integrated sensor is manufactured by surface silicon micromachining technology, has a high yield, a low manufacturing cost, and is compatible with IC. Each sensor component can work normally and has a certain performance, and thus can be applied to complex scenes and simultaneously detect six types of physical quantities.

[0085] The entire four-in-one monolithic integrated sensor occupies an area of ​​only 2 mm × 2 mm (specifically, the accelerometer 10 has a size of 900 μm × 1910 μm, the pressure sensor 20 has a size of 550 μm × 430 μm, the gas sensor 30 has a size of 1100 μm × 560 μm, and the humidity sensor 40 has a size of 570 μm × 570 μm).

[0086] The pressure and acceleration sensors are of the absolute pressure-piezoresistive type, so a cavity needs to be constructed. When an external load is applied to the pressure / acceleration sensitive diaphragm, the diaphragm will deform, which in turn will deform the polysilicon resistor, thereby changing the resistance value of the polysilicon resistor. The change is output through a Wheatstone bridge.

[0087] The cavity structure required in gas and humidity sensors reduces power consumption. The heating electrode in a gas sensor is used to reach the temperature required for the gas-sensitive material to react, while the test electrode outputs the change in resistance. A silicon dioxide layer is deposited between the heating and test electrodes as an insulating layer. When the measured object reacts with the sensitive material (such as the gas-sensitive material in a gas sensor or the humidity-sensitive material in a humidity sensor), the conductivity of the sensitive material changes, altering the total resistance between the sensitive material and the test electrode. This change is then output through the test electrode.

[0088] The completed four-in-one sensor, such as Figure 4A As shown in Figure 4B, the left half of the figure illustrates its specific structure under a microscope, while the right half shows a size comparison with a 1-cent coin. The detection limit of the pressure sensor was experimentally measured to be 5 μN, as shown in Figure 4B; the sensitivity of the accelerometer was 0.065 V / g, as... Figure 4C As shown; the gas sensor's response time is 150 s, as... Figure 4D As shown; the humidity sensor's humidity-sensitive range is 10%-97%RH, such as... Figure 4E As shown in the figure, it can be seen that each sensor can function normally.

[0089] By using a silicon surface to create cavities, the heat-insulating cavities required for the gas and humidity sensors were formed, thus avoiding the poor corrosion effect and excessively long corrosion time of traditional methods. By optimizing the process and adjusting the sequence of process steps, the pressure sensor, acceleration sensor, gas sensor, and humidity sensor were integrated into a single chip on a single side.

[0090] The above merely describes preferred embodiments of the present application, and is not intended to limit the scope of the present application. The above-described embodiments of the present application can be variously changed. Any simple, equivalent changes and modifications made according to the content of the claims and the specification of the present application are intended to fall within the scope of the present application. The present application is not limited by the above-described embodiments.

Claims

1. A method for fabricating a MEMS quad-in-one monolithic integrated sensor, used for integrating an accelerometer, a pressure sensor, a gas sensor, and a humidity sensor, characterized in that, include: Step S1: Provide a silicon wafer and deposit an isolation layer on the silicon wafer; Step S2: Using SiO2, respectively, protrusions for acceleration, pressure, gas, and humidity sensors are fabricated on the isolation layer, and etched pins adjacent to each protrusion are formed as sacrificial layers, thereby obtaining a silicon wafer with a sacrificial layer. Step S3: Deposit a layer of low-stress silicon nitride on the entire silicon wafer with the sacrificial layer as a structural layer and a sensitive film; Step S4: Fabricate a sensitive device on the sensitive diaphragm that changes based on the deformation of the sensitive diaphragm, the sensitive device including a sensitive resistor required for acceleration and pressure sensors; and fabricate test electrodes for a gas sensor and a humidity sensor on the sensitive diaphragm. Step S5: Etch the sensitive film above the corrosion pin to obtain a corrosion release hole penetrating the sensitive film; Step S6: Place the silicon wafer in the HF solution, allowing the HF solution to etch the sacrificial layer through the etching release holes. At the same time, observe the color of the protrusions under the sensitive film multiple times to see if they change. Stop etching when all the protrusions have changed color. Step S7: Deposit a multilayer material formed by alternating stacks of silicon nitride and silicon dioxide at the corrosion release holes to obtain a sealing layer to seal all corrosion release holes; Step S8: Coat the gas-sensitive material of the gas sensor and the sensitive material of the humidity sensor onto the test electrode of the gas sensor and the test electrode of the humidity sensor, respectively, to obtain a MEMS four-in-one monolithic integrated sensor.

2. The method for fabricating a MEMS quad-in-one monolithic integrated sensor according to claim 1, characterized in that, Step S2 specifically includes: Step S21: Deposit SiO2 on the isolation layer and perform photolithography and etching to pattern it and form the respective bosses of the acceleration, pressure, gas and humidity sensors at the positions corresponding to the acceleration, pressure, gas and humidity sensors. Step S22: Deposit another layer of SiO2 on the isolation layer, and perform photolithography and etching to pattern it and form etched pins adjacent to each boss.

3. The method for fabricating a MEMS quad-in-one monolithic integrated sensor according to claim 1, characterized in that, Step S4 specifically includes: Step S41: Deposit a layer of low-stress polysilicon on the sensitive film, perform boron ion implantation annealing on it, and then perform photolithography and etching on the polysilicon to pattern it so as to form the sensitive resistors of the acceleration and pressure sensors at the positions corresponding to the sensitive resistors of the acceleration and pressure sensors, respectively. Step S42: Deposit a layer of low-stress silicon nitride at the sensitive resistors of the acceleration and pressure sensors as a protective layer for the sensitive resistors of the acceleration and pressure sensors. Step S43: Fabricate electrode leads on the sensitive resistors of the accelerometer and pressure sensor respectively; Step S44: Fabricate test electrodes for the gas sensor and humidity sensor respectively on the sensitive membranes of the gas sensor and humidity sensor.

4. The method for fabricating a MEMS quad-in-one monolithic integrated sensor according to claim 3, characterized in that, Step S43 specifically includes: etching the protective layers of the sensitive resistors of the acceleration and pressure sensors respectively to form lead holes for the sensitive resistors of the acceleration and pressure sensors, and sputtering a layer of gold at the lead holes as electrode leads.

5. The method for fabricating a MEMS quad-in-one monolithic integrated sensor according to claim 3, characterized in that, Step S4 further includes: Step S45: Fabricating a mass block on the sensitive diaphragm at the accelerometer, wherein the mass block is made of copper and its thickness is less than 10 μm.

6. The method for fabricating a MEMS quad-in-one monolithic integrated sensor according to claim 3, characterized in that, In step S41, the thickness of the sensitive resistor is 4000 Å ~ 4500 Å, the ion implantation energy for implantation annealing is 60 keV, and the implantation dose is 5 × 10⁻⁶. 15 ions / cm 2 The annealing temperature is 1000 degrees Celsius, and nitrogen gas is introduced; in step S42, the thickness of the protective layer of the sensitive resistor is 1400 Å ~ 2000 Å; and in step S43, the thickness of the electrode lead is 3000 Å ~ 4000 Å.

7. The method for fabricating a MEMS quad-in-one monolithic integrated sensor according to claim 1, characterized in that, In step S7, the sealing layer is obtained, specifically by: depositing silicon nitride, silicon dioxide, and silicon nitride using PECVD to obtain a multilayer material in the form of silicon nitride-silicon dioxide-silicon nitride, and performing photolithography and etching to pattern the multilayer material, thereby obtaining the sealing layer.

8. The method for fabricating a MEMS quad-in-one monolithic integrated sensor according to claim 1, characterized in that, The silicon wafer is a single-shot N+ type. <100> Silicon wafer; the isolation layer is low-stress silicon nitride with a thickness of 2000 Å ~ 5000 Å; the thickness of the boss is 8000 Å ~ 20000 Å, and the thickness of the etched pins is 2000 Å ~ 4000 Å.

9. The method for fabricating a MEMS quad-in-one monolithic integrated sensor according to claim 1, characterized in that, The gas-sensitive material of the gas sensor is SnO2 / TiO2, and the humidity-sensitive material of the humidity sensor is ZnO / PEG. The gas-sensitive material of the gas sensor and the humidity-sensitive material of the humidity sensor are obtained by spotting the materials onto the test electrodes of the gas and humidity sensors.

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