Preparation method of MEMS (Micro Electro Mechanical System) multi-type piezoresistive pressure sensor based on SON-SOI (Silicon On Insulator) composite structure

Abstract

The invention discloses a preparation method of MEMS (Micro Electro Mechanical System) multi-type piezoresistive pressure sensors based on an SON-SOI (Silicon On Insulator) composite structure, and belongs to the field of MEMS. According to the invention, a high-precision double-sided photoetching overlay process technology, an SON-SOI composite structure technology, an N-type isolation barrier structure process technology, a P-type piezoresistor strip structure process technology, a high-temperature metal material layer interconnection structure process technology, a back thinning process technology and a back cavity deep groove structure dry etching process technology are adopted; the method for preparing various types of MEMS piezoresistive pressure sensors based on an SON-SOI composite structure is realized by adopting a back cavity deep groove structure wet etching process technology and the like, and the types of the prepared MEMS piezoresistive pressure sensors comprise an absolute pressure type, a gauge pressure type, a differential pressure type and an absolute pressure and gauge pressure / differential pressure integrated type; the MEMS pressure sensor has the advantages that various types of MEMS pressure sensor process platforms are unified, the manufacturing process flow is obviously simplified, the material waste is reduced, the production cost is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the field of MEMS technology, and in particular to a method for preparing MEMS various types of piezoresistive pressure sensors based on a SON-SOI composite structure. Background Art

[0002] MEMS piezoresistive pressure sensor is a type of sensor based on micro-electromechanical system (MEMS) technology, which uses the piezoresistive effect of materials to measure pressure. This type of sensor has the characteristics of high sensitivity, miniaturization, low cost and suitability for mass production, and is widely used in medical, industrial control, consumer electronics and other fields.

[0003] The three common types of MEMS piezoresistive pressure sensors are absolute pressure type, gauge pressure type, and differential pressure type. Absolute pressure type piezoresistive pressure sensors are used to measure pressure relative to vacuum or reference pressure. Such sensor elements are usually located in a closed cavity structure, with one side of the cavity being vacuum or reference pressure, and the other side being exposed to the pressure environment to be measured. They are often used in aerospace, meteorology, and automotive engine management systems. Gauge pressure type piezoresistive pressure sensors are used to measure pressure relative to atmospheric pressure. Such sensors are usually exposed to the pressure to be measured, and the other side is exposed to the atmospheric environment. They are often used in sphygmomanometers, industrial equipment pressure monitoring, etc. Differential pressure type piezoresistive pressure sensors are used to measure the pressure difference between two different points. The two ports of such sensors are exposed to two different pressure environments respectively. The signal output by the sensor is proportional to the pressure difference at both ends. They are often used in filter blockage monitoring, flow measurement, and liquid level measurement.

[0004] At present, the preparation of the above three types of MEMS piezoresistive pressure sensor chips on the market requires different process flows and equipment, multiple production lines and special processing techniques, which increases the complexity of the process; since different types of pressure sensors need to switch to different process flows, the equipment needs to switch to different operating states, especially in small batch production or simultaneous processing of multiple types of products, resulting in low production efficiency; multiple production lines and process flows are required, resulting in high manufacturing and equipment maintenance costs; traditional processing models are difficult to quickly respond to market demand for new sensors, and the iteration speed is slow. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing various types of MEMS piezoresistive pressure sensors based on a SON-SOI composite structure, so as to solve the problems in the background technology.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing various types of MEMS piezoresistive pressure sensors based on a SON-SOI composite structure, comprising:

[0007] Step 1: Provide unlimited thickness, N <100> , a double-polished substrate material sheet, and a double-sided photolithography alignment mark structure photolithography process and a dry etching process are performed on the back side of the substrate material sheet;

[0008] Step 2: subjecting the substrate material sheet with the double-sided photolithography alignment mark structure processed on the back to a deep silicon slot array photolithography process, a dry etching process and a photoresist removal process;

[0009] Step 3: Perform high-temperature annealing in the epitaxial equipment to form a SON vacuum or reference pressure cavity structure; grow silicon dioxide layers on the front and back of the substrate material sheet through a thermal oxidation process in the furnace tube, where the silicon dioxide layer grown on the front is the BOX oxide layer of Cavity-SOI; grow a single crystal silicon layer in the epitaxial equipment to form a SON-SOI composite structure;

[0010] Step 4: thermal oxidation process is performed again in the furnace tube to grow silicon dioxide layer on the front and back of the substrate material sheet of the SON-SOI composite structure, N-type isolation barrier structure photolithography process, with glue implantation, the implanted ion type is phosphorus, the implantation energy is 80-100keV, the implantation dose is 4E15-9E15, and the implantation angle is 7°-10°; remove the photoresist;

[0011] Step 5: Photolithography process of P-type varistor strip structure, injection of adhesive, and removal of photoresist;

[0012] Step 6: P-type interconnect structure photolithography process, adhesive injection, and photoresist removal;

[0013] Step 7: Using a low-pressure chemical vapor deposition process in the furnace tube, a silicon dioxide layer and a silicon nitride layer are sequentially deposited on the front and back of the device, an annealing process is performed, contact hole structure is photolithographically performed, the silicon dioxide layer and the silicon nitride layer on the front are dry-etched, and the photoresist is removed;

[0014] Step 8: photoresist coating process, high temperature metal material layer evaporation process coating, photoresist stripping, forming a metal interconnect structure; or, high temperature metal material layer sputtering process, photoresist lithography process, metal interconnect structure etching process, removing photoresist;

[0015] Step 9: Deposit a passivation layer on the front of the device through a plasma enhanced chemical vapor deposition process, perform passivation layer photolithography, perform a passivation layer structure dry etching process, remove the photoresist, and perform an alloy process.

[0016] In one embodiment, when a MEMS absolute pressure type piezoresistive pressure sensor chip is prepared, the thickness of the substrate material sheet is adjusted through a back thinning process according to the MEMS pressure sensor chip packaging requirement of 200 μm to 600 μm to complete the preparation of the MEMS absolute pressure type pressure sensor chip.

[0017] In one embodiment, when a MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor chip based on a wet etching process is selected for preparation, a back dielectric layer photolithography process and a back dielectric layer dry etching process are performed to remove the photoresist; the front side is protected by glue coating, and the protective glue is resistant to corrosion by strong alkali and strong acid corrosive liquids; KOH or TMAH wet etching is performed on the back cavity deep groove structure; the SOI intermediate oxide layer is removed by a BOE wet etching process, and the corrosion surface of the back cavity is checked for dehydration, indicating that the silicon dioxide layer has been removed cleanly; the front protective glue is removed to complete the preparation of the MEMS gauge pressure type or differential pressure type pressure sensor chip.

[0018] In one embodiment, when a MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor chip based on a dry etching process is selected for preparation, a back dielectric layer photolithography process and a back dielectric layer dry etching process are performed; the front side is protected by glue coating, and the protective glue has corrosion resistance to strong alkali and strong acid corrosive liquids; a back cavity deep groove structure dry etching process is performed; the SOI intermediate oxide layer is removed by a BOE wet etching process, and the corrosion surface of the back cavity is checked for dehydration, indicating that the silicon dioxide layer has been removed cleanly; the back photoresist is removed; the front protective glue is removed, and the preparation of the MEMS gauge pressure type or differential pressure type pressure sensor chip is completed.

[0019] In one embodiment, when selecting to prepare MEMS various types of piezoresistive pressure sensor integrated chips based on a wet etching process, a back dielectric layer photolithography process and a back dielectric layer dry etching process are performed on the preparation area of ​​the MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor to remove the photoresist; the front side is protected by glue coating, and the back cavity deep groove structure is wet-etched with KOH or TMAH; the SOI intermediate oxide layer is removed by a BOE wet etching process, and the corrosion surface of the back cavity is checked for dehydration, indicating that the silicon dioxide layer has been removed cleanly; the front protective glue is removed, and the preparation of the MEMS gauge pressure type or differential pressure type pressure sensor chip is completed.

[0020] In one embodiment, when selecting to prepare MEMS various types of piezoresistive pressure sensor integrated chips based on a dry etching process, the preparation area of ​​the MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor is subjected to a back dielectric layer photolithography process and a back dielectric layer dry etching process; the front side is protected by glue coating, and a back cavity deep groove structure dry etching process is performed; the SOI intermediate oxide layer is removed by a BOE wet etching process, and the corrosion surface of the back cavity is checked for dehydration, indicating that the silicon dioxide layer has been removed cleanly; the back photoresist is removed; the front protective glue is removed, and the preparation of the MEMS gauge pressure type or differential pressure type pressure sensor chip is completed.

[0021] In one embodiment, the hole array is a symmetrical regular structure of square, circle, hexagon or octagon, with a width of 0.4 μm to 1.2 μm, a spacing of 0.4 μm to 1.2 μm, and an etching depth of 10 μm to 50 μm.

[0022] In one embodiment, in the fifth step, the implanted ion species is boron, the implantation energy is 25-80 keV, the implantation dose is 1.0E14-9E14, and the implantation angle is 7°-10°.

[0023] In one embodiment, in the sixth step, the implanted ion species is boron, the implantation energy is 25-80 keV, the implantation dose is 4E15-9E15, and the implantation angle is 7°-10°.

[0024] In one embodiment, the thickness of the high temperature metal material layer is 1 μm to 2 μm, and the high temperature metal material is selected from platinum, titanium / platinum / gold multilayer structure, nickel-chromium alloy, aluminum / copper alloy.

[0025] In one embodiment, in the ninth step, the passivation protective layer material is a single-layer silicon nitride layer or a stack of silicon dioxide and silicon nitride, wherein the stack of silicon dioxide and silicon nitride is a silicon dioxide layer and a silicon nitride layer deposited in sequence on the front side of the substrate material sheet that has completed the eighth step process, and the overall thickness of the passivation protective layer is 0.2μm to 1.2μm; the alloying temperature is 400℃ to 500℃, and the alloying time is 30min to 200min.

[0026] The present invention provides a method for preparing a MEMS multi-type piezoresistive pressure sensor based on a SON-SOI composite structure, which has the following beneficial effects:

[0027] (1) The present invention realizes a MEMS multi-type pressure sensor based on a SON-SOI composite structure and a preparation method thereof. The MEMS pressure sensor types that can be prepared include absolute pressure type, gauge pressure type, differential pressure type, and absolute pressure and gauge pressure / differential pressure integrated type; through innovative process design, the preparation method of "single set of main process-different types of pressure sensors" is successfully realized, breaking through the compatibility problem of MEMS different types of pressure sensor preparation processes, unifying the MEMS multi-type pressure sensor process platform, significantly simplifying the manufacturing process and reducing material waste, reducing production costs, and improving production efficiency;

[0028] (2) The present invention accurately controls the thickness of the single crystal top silicon layer of the SON-SOI composite structure through the epitaxial process, innovatively realizes the process processing mode of using a single set of photolithography layout structure to complete a variety of pressure range chips, speeds up the R&D cycle, reduces R&D costs, and responds to new market demands more quickly and flexibly;

[0029] (3) The present invention manufactures a closed vacuum or reference pressure cavity structure on an ordinary substrate material sheet. This innovative structural design provides a layer of super protection for the pressure sensor, making the pressure measurement more accurate and stable. The present invention uses the N-type isolation barrier structure process technology on the N-type single crystal top silicon of the SON-SOI composite structure substrate material sheet to improve the anti-interference ability and reliability of the MEMS pressure sensor chip. The high-temperature metal material layer interconnection structure process technology improves the high temperature resistance of the MEMS pressure sensor chip. Therefore, compared with the MEMS pressure sensors with traditional processing technology, the MEMS various types of pressure sensors based on the SON-SOI composite structure have the advantages of higher accuracy, higher reliability, stronger anti-interference ability, wider operating temperature range and more miniaturized structure size, which can meet the needs of more stringent environmental applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the cross-sectional structure of the double-sided photolithography alignment mark structure preparation process.

[0031] Figure 2 It is a schematic diagram of the cross-sectional structure of the deep silicon slot array structure preparation process.

[0032] Figure 3 It is a schematic diagram of the cross-sectional structure of the SON-SOI composite structure preparation process.

[0033] Figure 4 It is a schematic diagram of the cross-sectional structure of the N-type isolation barrier structure preparation process.

[0034] Figure 5 It is a schematic diagram of the cross-sectional structure of the preparation process of the P-type varistor strip structure.

[0035] Figure 6 It is a schematic diagram of the cross-sectional structure of the preparation process of the P-type interconnect structure.

[0036] Figure 7 It is a schematic diagram of the cross-sectional structure of the contact hole structure preparation process.

[0037] Figure 8 It is a schematic diagram of the cross-sectional structure of the metal interconnect structure preparation process.

[0038] Fig. 9 It is a schematic diagram of the cross-sectional structure of the passivation protection layer structure preparation process.

[0039] Figure 10-a It is a cross-sectional structural schematic diagram of the MEMS absolute pressure type piezoresistive pressure sensor chip structure preparation process.

[0040] Figure 10-b It is a schematic diagram of the cross-sectional structure of a MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor chip preparation process based on a wet etching process.

[0041] Figure 10-c It is a schematic cross-sectional structure diagram of the preparation process of a MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor chip based on a dry etching process.

[0042] Figure 10-d It is a schematic diagram of the cross-sectional structure of the preparation process of MEMS various types of piezoresistive pressure sensor integrated chips based on wet etching technology.

[0043] Figure 10-e It is a schematic diagram of the cross-sectional structure of the preparation process of MEMS various types of piezoresistive pressure sensor integrated chips based on dry etching technology. DETAILED DESCRIPTION

[0044] The following is a further detailed description of a method for preparing a MEMS multi-type piezoresistive pressure sensor based on a SON-SOI composite structure proposed by the present invention in combination with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer according to the following description. It should be noted that the accompanying drawings are all in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

[0045] The present invention provides a MEMS multi-type piezoresistive pressure sensor based on a SON-SOI composite structure and a preparation method thereof. Through innovative structure and process design, the preparation method of "single set of main body process-different types of pressure sensors" is successfully realized, breaking through the compatibility problem of MEMS different types of pressure sensor preparation processes, unifying the MEMS multi-type pressure sensor process platform, significantly simplifying the manufacturing process flow and reducing material waste, reducing production costs, and improving production efficiency.

[0046] The present invention uses an epitaxial process to precisely control the thickness of the single crystal top silicon layer of the SON-SOI composite structure, innovatively realizing a process processing mode of using a single set of photolithography layout structures to complete a variety of pressure range chips, accelerating the R&D cycle and reducing R&D costs; it can flexibly adjust the design, quickly respond to market demand, and support faster product iteration and upgrades. Through innovative structural and process design, the present invention enables various types of MEMS pressure sensors based on the SON-SOI composite structure to have higher accuracy, higher reliability, stronger anti-interference ability, wider operating temperature range, and more miniaturized structural dimensions compared to MEMS pressure sensors using traditional processing technology, and can meet more stringent environmental application requirements.

[0047] According to the technical solution provided by the present invention, the specific process flow of the method includes the following steps:

[0048] Step 1: Provide unlimited thickness, N <100> , double-polished substrate material sheet, double-sided photolithography alignment mark structure photolithography process and dry etching process are performed on the back of the substrate material sheet, the double-sided photolithography overlay accuracy requirement is ≤0.5μm, and the etching depth is generally 0.2μm~0.5μm, such as Figure 1 shown.

[0049] Step 2: The N <100> , double-polished substrate material sheet is subjected to deep silicon slot array photolithography process, dry etching process and photoresist removal process, the hole array is a symmetrical regular structure such as square, circular, hexagonal, octagonal, etc., the width is generally 0.4μm~1.2μm, the spacing is generally 0.4μm~1.2μm, the etching depth is generally 10μm~50μm, such as Figure 2 shown.

[0050] The third step: high-temperature annealing treatment is carried out in the epitaxial equipment to form a SON vacuum or reference pressure cavity structure. Generally, the annealing temperature is higher than 1000-1300°C, and the reaction gas is hydrogen (H2); a silicon dioxide layer is grown on the front and back sides of the substrate material sheet through a thermal oxidation process in the furnace tube. The thickness of the silicon dioxide layer on the front and back sides is 0.5μm-1μm respectively, and the silicon dioxide layer grown on the front side is the BOX oxide layer of Cavity-SOI; a single crystal silicon layer of a certain thickness is grown in the epitaxial equipment. The temperature of the epitaxial growth of the single crystal silicon layer is 1000-1300°C. The thickness of the single crystal silicon layer depends on the pressure range requirements of the MEMS pressure sensor product, forming a SON-SOI composite structure, such as Figure 3 shown.

[0051] The 4th step: in the furnace tube, through the thermal oxidation process again, the silicon dioxide layer is grown on the front and back sides of the substrate material sheet of the SON-SOI composite structure (because the thermal oxidation process in the 3rd step has grown the silicon dioxide layer on the back side of the substrate material sheet, the back side is blocked by the silicon dioxide layer generated for the first time in the thermal oxidation process again, and the "oxygen" or "mixed gas of water vapor and oxygen" reacts with silicon through the silicon dioxide layer for the first time. The thickness of the silicon dioxide layer generated is tiny, and therefore not shown in the figure), the thickness of the silicon dioxide layer is 0.1 μm~0.2 μm; N-type isolation barrier structure photolithography process, with glue injection, the implanted ion species is phosphorus (P), the implantation energy is 80~100 keV, the implantation dose is 4E15~9E15, and the implantation angle is 7 °~10 °; remove the photoresist, such as Figure 4 shown.

[0052] Step 5: Photolithography process of P-type varistor strip structure, with glue injection, the injection ion type is boron (Boron, B), the injection energy is 25~80keV, the injection dose is 1.0E14~9E14, and the injection angle is 7°~10°; remove the photoresist, such as Figure 5 shown.

[0053] Step 6: P-type interconnect structure photolithography process, with resin injection, the injection ion type is boron (Boron, B), the injection energy is 25~80keV, the injection dose is 4E15~9E15, and the injection angle is 7°~10°; remove the photoresist, such as Figure 6 shown.

[0054] Step 7: Through the LPCVD (low pressure chemical vapor deposition) process in the furnace tube, a silicon dioxide layer and a silicon nitride layer are sequentially deposited on the front and back of the substrate material sheet that has completed the sixth step process. The thickness of the silicon dioxide layer is 0.2μm to 0.5μm, and the thickness of the silicon nitride layer is 0.1μm to 0.2μm; annealing process, the annealing temperature is 950℃ to 1200℃, and the annealing time is 30min to 150min; contact hole structure lithography, the contact hole size is 5μm to 20μm, dry etching the silicon dioxide layer and silicon nitride layer on the front side, and removing the photoresist, such as Figure 7 shown.

[0055] Step 8: Photoresist coating process, high temperature metal material layer evaporation process coating, lift-off photoresist, and form metal interconnection structure. Alternatively, high temperature metal material layer sputtering process, photoresist photolithography process, metal interconnection structure etching process, and remove photoresist. The thickness of the high temperature metal material layer is 1μm to 2μm. The high temperature metal material can be selected from platinum (Platinum, Pt), titanium / platinum / gold (Ti / Pt / Au) multilayer structure, nickel-chromium alloy (Nickel-ChromiumAlloy, NiCr) aluminum / copper alloy (Al / Cu), etc. Figure 8 shown.

[0056] Step 9: Deposit a passivation protective layer on the front of the substrate material sheet after the eighth step by PECVD (plasma enhanced chemical vapor deposition) process. The passivation protective layer material can be a single silicon nitride layer or a stack of silicon dioxide and silicon nitride, wherein the stack of silicon dioxide and silicon nitride is a silicon dioxide layer and a silicon nitride layer deposited in sequence on the front of the substrate material sheet after the eighth step, and the overall thickness of the passivation protective layer is 0.2μm to 1.2μm; perform a passivation protective layer photolithography process, a passivation protective layer structure dry etching process, and remove the photoresist; alloy process, the alloy temperature is 400℃ to 500℃, the alloy time is 30min to 200min, such as Fig. 9 shown.

[0057] Step 10-a: When choosing to prepare a MEMS absolute pressure type piezoresistive pressure sensor chip, according to the MEMS pressure sensor chip packaging requirement thickness of 200μm to 600μm, adjust the thickness of the substrate material sheet through the back thinning process to complete the MEMS absolute pressure type pressure sensor chip preparation, such as Figure 10-a shown.

[0058] Step 10-b: When choosing to prepare a MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor chip based on a wet etching process, the back dielectric layer is subjected to a photolithography process, the back dielectric layer is subjected to a dry etching process, and the photoresist is removed; the front side is coated with glue for protection, and the thickness of the protective glue is 5μm to 10μm, and the protective glue is required to be resistant to strong alkali and strong acid corrosion liquids; the back cavity deep groove structure is subjected to KOH or TMAH wet etching, and the corrosion temperature is 70℃ to 80℃; the SOI intermediate oxide layer is removed by a BOE wet etching process, and the BOE etching rate is 100nm / min to 1000nm / min. Check that the corrosion surface of the back cavity is dehydrated, indicating that the silicon dioxide layer has been removed cleanly; remove the front protective glue, and complete the preparation of the MEMS gauge pressure type or differential pressure type pressure sensor chip, such as Figure 10-b shown.

[0059] Step 10-c: When choosing to prepare a MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor chip based on a dry etching process, the back dielectric layer photolithography process and the back dielectric layer dry etching process are used; the front side is coated with glue for protection, and the thickness of the protective glue is 5μm to 10μm, and the protective glue is required to be resistant to strong alkali and strong acid corrosion liquids; the back cavity deep groove structure dry etching process, the dry etching process adopts deep reactive ion etching (DRIE) with a high selectivity of Si to SiO2 of 150:1 to 220:1, and the etching gas is sulfur hexafluoride (SF6); the BOE wet etching process removes the SOI intermediate oxide layer, and the BOE etching rate is 100nm / min to 1000nm / min. Check that the corrosion surface of the back cavity cavity is dehydrated, indicating that the silicon dioxide layer has been removed cleanly; remove the back photoresist; remove the front protective glue, and complete the preparation of the MEMS gauge pressure type or differential pressure type pressure sensor chip, such as Figure 10-c shown.

[0060] Step 10-d: When choosing to prepare MEMS various types of piezoresistive pressure sensor integrated chips based on wet etching process, perform back dielectric layer photolithography process and back dielectric layer dry etching process on the preparation area of ​​MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor to remove photoresist; apply glue protection on the front side, the protective glue has the corrosion resistance of strong alkali and strong acid corrosive liquid; perform KOH or TMAH wet etching on the back cavity deep groove structure; remove the SOI intermediate oxide layer through BOE wet etching process, check the dehydration state of the corrosion surface of the back cavity cavity, indicating that the silicon dioxide layer has been removed cleanly; remove the front protective glue, and complete the preparation of MEMS gauge pressure type or differential pressure type pressure sensor chip, such as Figure 10-d shown.

[0061] Step 10-e: When choosing to prepare MEMS various types of piezoresistive pressure sensor integrated chips based on dry etching process, perform back dielectric layer photolithography process and back dielectric layer dry etching process on the preparation area of ​​MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor; apply glue protection on the front side, the protective glue has the corrosion resistance of strong alkali and strong acid corrosive liquid; perform back cavity deep groove structure dry etching process; remove SOI middle oxide layer through BOE wet etching process, check the corrosion surface of back cavity cavity for dehydration, indicating that silicon dioxide layer is removed cleanly; remove back photoresist; remove front protective glue, and complete the preparation of MEMS gauge pressure type or differential pressure type pressure sensor chip, such as Figure 10-e shown.

[0062] The present invention realizes a method for preparing various types of MEMS piezoresistive pressure sensors based on a SON-SOI composite structure through high-precision double-sided photolithography overlay technology, SON-SOI composite structure technology, N-type isolation barrier structure technology, P-type varistor strip structure technology, high-temperature metal material layer interconnection structure technology, back thinning technology, back cavity deep groove structure dry etching technology, back cavity deep groove structure wet etching technology, etc. The types of MEMS piezoresistive pressure sensors that can be prepared include absolute pressure type, gauge pressure type, differential pressure type, and absolute pressure and gauge pressure / differential pressure integrated type. The present invention successfully realizes the preparation method of "single set of main body process-different types of pressure sensors" through innovative structure and process design, breaks through the compatibility problem of MEMS different types of pressure sensor preparation processes, unifies the MEMS various types of pressure sensor process platforms, significantly simplifies the manufacturing process flow and reduces material waste, reduces production costs, and improves production efficiency.

[0063] The present invention accurately controls the thickness of the single crystal top silicon layer of the SON-SOI composite structure through the epitaxial process, and innovatively realizes the process processing mode of completing various pressure range chips using a single set of photolithography layout structure, which speeds up the R&D cycle and reduces R&D costs; it can flexibly adjust the design, quickly respond to market demand, and support faster product iteration and upgrading.

[0064] The present invention manufactures a closed vacuum or reference pressure cavity structure on an ordinary substrate material sheet. This innovative structural design provides a layer of super protection for the pressure sensor, making the pressure measurement more accurate and stable. The present invention uses the N-type isolation barrier structure process technology on the N-type single crystal top silicon of the SON-SOI composite structure substrate material sheet to improve the anti-interference ability and reliability of the MEMS pressure sensor chip. The high-temperature metal material layer interconnection structure process technology improves the high temperature resistance of the MEMS pressure sensor chip. Therefore, compared with the MEMS pressure sensors with traditional processing technology, various types of MEMS pressure sensors based on the SON-SOI composite structure have the advantages of higher accuracy, higher reliability, stronger anti-interference ability, wider operating temperature range and more miniaturized structural size, which can meet the needs of more stringent environmental applications.

[0065] The above description is only a description of the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention. Any changes or modifications made by a person skilled in the art in the field of the present invention based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A method for preparing MEMS multi-type piezoresistive pressure sensors based on SON-SOI composite structure, characterized in that: include: Step 1: Provide unlimited thickness, N <100> , a double-polished substrate material sheet, and a double-sided photolithography alignment mark structure photolithography process and a dry etching process are performed on the back side of the substrate material sheet; Step 2: subjecting the substrate material sheet with the double-sided photolithography alignment mark structure processed on the back to a deep silicon slot array photolithography process, a dry etching process and a photoresist removal process; Step 3: Perform high-temperature annealing in the epitaxial equipment to form a SON vacuum or reference pressure cavity structure; grow silicon dioxide layers on the front and back of the substrate material sheet through a thermal oxidation process in the furnace tube, where the silicon dioxide layer grown on the front is the BOX oxide layer of Cavity-SOI; grow a single crystal silicon layer in the epitaxial equipment to form a SON-SOI composite structure; Step 4: thermal oxidation process is performed again in the furnace tube to grow silicon dioxide layer on the front and back of the substrate material sheet of the SON-SOI composite structure, N-type isolation barrier structure photolithography process, with glue implantation, the implanted ion type is phosphorus, the implantation energy is 80-100keV, the implantation dose is 4E15-9E15, and the implantation angle is 7°-10°; remove the photoresist; Step 5: Photolithography process of P-type varistor strip structure, injection of adhesive, and removal of photoresist; Step 6: P-type interconnect structure photolithography process, adhesive injection, and photoresist removal; Step 7: Using a low-pressure chemical vapor deposition process in the furnace tube, a silicon dioxide layer and a silicon nitride layer are sequentially deposited on the front and back of the device, an annealing process is performed, contact hole structure is photolithographically performed, the silicon dioxide layer and the silicon nitride layer on the front are dry-etched, and the photoresist is removed; Step 8: photoresist coating process, high temperature metal material layer evaporation process coating, photoresist stripping, forming a metal interconnect structure; or, high temperature metal material layer sputtering process, photoresist lithography process, metal interconnect structure etching process, removing photoresist; Step 9: Deposit a passivation layer on the front of the device through a plasma enhanced chemical vapor deposition process, perform passivation layer photolithography, perform a passivation layer structure dry etching process, remove the photoresist, and perform an alloy process.

2. The method for preparing MEMS multi-type piezoresistive pressure sensors based on SON-SOI composite structure according to claim 1, characterized in that: When choosing to prepare a MEMS absolute pressure type piezoresistive pressure sensor chip, according to the MEMS pressure sensor chip packaging requirement thickness of 200μm to 600μm, the thickness of the substrate material sheet is adjusted through a back thinning process to complete the preparation of the MEMS absolute pressure type pressure sensor chip.

3. The method for preparing MEMS multi-type piezoresistive pressure sensors based on SON-SOI composite structure according to claim 1, characterized in that: When a MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor chip based on a wet etching process is selected for preparation, a back dielectric layer photolithography process and a back dielectric layer dry etching process are performed to remove the photoresist; The front side is protected by glue, and the protective glue is resistant to corrosion by strong alkali and strong acid corrosive liquids; the back cavity deep groove structure is wet-etched by KOH or TMAH; the SOI intermediate oxide layer is removed by BOE wet-etching process, and the corrosion surface of the back cavity is checked for dehydration, indicating that the silicon dioxide layer has been removed cleanly; the front protective glue is removed to complete the preparation of MEMS gauge pressure type or differential pressure type pressure sensor chip.

4. The method for preparing MEMS multi-type piezoresistive pressure sensors based on SON-SOI composite structure according to claim 1, characterized in that: When a MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor chip based on a dry etching process is selected for preparation, a back dielectric layer photolithography process and a back dielectric layer dry etching process are performed; the front side is coated with glue for protection, and the protective glue is resistant to strong alkali and strong acid corrosion liquids; a back cavity deep groove structure dry etching process is performed; the SOI intermediate oxide layer is removed by a BOE wet etching process, and the corrosion surface of the back cavity is checked for dehydration, indicating that the silicon dioxide layer has been removed cleanly; the back photoresist is removed; Remove the front protective glue and complete the preparation of the MEMS gauge pressure type or differential pressure type pressure sensor chip.

5. The method for preparing MEMS multi-type piezoresistive pressure sensors based on SON-SOI composite structure according to claim 1, characterized in that: When a MEMS multi-type piezoresistive pressure sensor integrated chip based on a wet etching process is selected for preparation, a back dielectric layer photolithography process and a back dielectric layer dry etching process are performed on the preparation area of ​​the MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor to remove the photoresist; The front side is protected by glue, and the back cavity deep groove structure is wet-etched by KOH or TMAH. The SOI intermediate oxide layer is removed by BOE wet-etching process, and the corrosion surface of the back cavity is checked for dehydration, indicating that the silicon dioxide layer has been removed cleanly. The front protective glue is removed to complete the preparation of MEMS gauge pressure type or differential pressure type pressure sensor chip.

6. The method for preparing MEMS multi-type piezoresistive pressure sensors based on SON-SOI composite structure according to claim 1, characterized in that: When selecting to prepare MEMS various types of piezoresistive pressure sensor integrated chips based on dry etching process, the preparation area of ​​MEMS gauge pressure type or differential pressure type piezoresistive pressure sensor is subjected to back dielectric layer photolithography process and back dielectric layer dry etching process; the front side is coated with glue for protection, and the back cavity deep groove structure is dry-etched; the SOI intermediate oxide layer is removed by BOE wet etching process, and the corrosion surface of the back cavity is checked for dehydration, indicating that the silicon dioxide layer is removed cleanly; the back photoresist is removed; Remove the front protective glue and complete the preparation of the MEMS gauge pressure type or differential pressure type pressure sensor chip.

7. The method for preparing MEMS multi-type piezoresistive pressure sensors based on SON-SOI composite structure according to claim 1, characterized in that: The hole array is a symmetrical regular structure of square, circle, hexagon and octagon, with a width of 0.4 μm to 1.2 μm, a spacing of 0.4 μm to 1.2 μm, and an etching depth of 10 μm to 50 μm.

8. The method for preparing MEMS various types of piezoresistive pressure sensors based on SON-SOI composite structure according to claim 1, characterized in that: In the fifth step, the implanted ion species is boron, the implantation energy is 25-80 keV, the implantation dose is 1.0E14-9E14, and the implantation angle is 7°-10°.

9. The method for preparing MEMS various types of piezoresistive pressure sensors based on a SON-SOI composite structure according to claim 1, characterized in that: In the sixth step, the implanted ion species is boron, the implantation energy is 25-80 keV, the implantation dose is 4E15-9E15, and the implantation angle is 7°-10°.

10. The method for preparing MEMS various types of piezoresistive pressure sensors based on a SON-SOI composite structure according to claim 1, characterized in that: The thickness of the high temperature metal material layer is 1 μm to 2 μm, and the high temperature metal material is selected from platinum, titanium / platinum / gold multilayer structure, nickel-chromium alloy, aluminum / copper alloy.

11. The method for preparing MEMS multi-type piezoresistive pressure sensors based on SON-SOI composite structure according to claim 1, characterized in that: In the ninth step, the passivation protective layer material is a single-layer silicon nitride layer or a stack of silicon dioxide and silicon nitride, wherein the stack of silicon dioxide and silicon nitride is a silicon dioxide layer and a silicon nitride layer deposited in sequence on the front side of the substrate material sheet that has completed the eighth step process, and the overall thickness of the passivation protective layer is 0.2μm to 1.2μm; the alloying temperature is 400℃ to 500℃, and the alloying time is 30min to 200min.

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