MEMS pressure sensor manufacturing method capable of forming TSV hole in advance

Abstract

The invention provides a manufacturing method of an MEMS pressure sensor. The manufacturing method mainly comprises the following steps: 1) providing an SOI substrate; 2) forming a Wheatstone bridge piezoresistor; (3) forming a film Contact layer; (4) etching a Contact hole; 5) performing film formation and etching on a metal conductive substance; (6) etching the SOI substrate to form a vacuum cavity groove; 7) bonding the SOI substrate and the second substrate to form a vacuum cavity; 8) filling the TSV with a conductive material; (9) TSV organic matter filling and pad etching are carried out; and 10) etching an opening on the back surface of the SOI substrate. The key innovation of the invention lies in that the TSV hole is formed in the second substrate in advance, accurate alignment and bonding can be realized, and the defect caused by bombardment of a subsequent etching process on the whole structure is avoided. By means of the method, the technological process is simpler and easier to implement, and the performance and reliability of the sensor are improved.

Description

Technical Field

[0001] The present invention relates to the field of micro-electromechanical systems (MEMS) technology, and in particular to a method for manufacturing a MEMS pressure sensor by forming a TSV hole in advance. Background Art

[0002] Pressure sensors are currently widely used in the automotive, medical and aerospace fields. Their basic principle is to convert the pressure change or deformation change into an electrical signal. Among them, MEMS pressure sensors are mainly piezoresistive and capacitive. The current mainstream MEMS pressure sensor is based on the principle of piezoresistors, that is, piezoresistive pressure sensors, which are widely used in automotive systems to test key parameters such as airbag pressure, fuel pressure, engine oil pressure, and intake pipe pressure.

[0003] In view of the technical improvement of MEMS sensors, existing patent documents have provided methods for improving the sensitivity and measurement range of MEMS pressure sensors. For example, patent document CN110775940B discloses a method for manufacturing a MEMS sensor component, and a MEMS sensor component manufactured by the method. The core principle is filter membrane preparation, buffer layer formation, filter membrane material deposition, heating separation, and buffer layer removal to protect the nano-thin film from damage caused by conventional mechanical transfer processes.

[0004] However, there are still problems and defects such as low sensitivity, which limit its wider application. In addition, some existing sensors are not sensitive enough to slight pressure changes, which affects the measurement accuracy. In some harsh environments, such as high humidity or environments containing corrosive substances, the sensors are also easily damaged. With the development of science and technology, the market demand for MEMS is expanding, and it is imperative to solve the current problems.

[0005] Therefore, the present invention designs and provides a method for manufacturing a MEMS pressure sensor with TSV holes formed in advance, and achieves accurate, sensitive and stable pressure measurement through special process treatment. Summary of the invention

[0006] The purpose of the present invention is to provide a method for manufacturing a MEMS pressure sensor with TSV holes formed in advance, integrating an improved cross-beam structure design, multi-layer composite thin film technology, enhanced mechanical stability design, pre-opening of TSV holes, and precise alignment and bonding, so as to achieve stress concentration and improve the sensitivity of the device, while increasing the overall stiffness of the structure and improving the linearity and dynamic response characteristics of the sensor.

[0007] To achieve the above objectives, the present invention proposes the following technical solutions. A method for manufacturing a MEMS pressure sensor with TSV holes formed in advance, the main steps of which include 1) providing an SOI substrate; 2) forming a Wheatstone bridge piezoresistor; 3) forming a contact layer; 4) etching the contact hole; 5) forming a film and etching a metal conductive material; 6) etching a vacuum cavity groove formed on the SOI substrate; 7) bonding the SOI substrate and a second substrate to form a vacuum cavity; 8) filling the TSV hole with a conductive material; 9) filling the TSV with an organic material and etching the pad; 10) etching an opening on the back of the SOI substrate. The key innovation of the present invention is that the TSV hole is formed in advance on the second substrate, which can be accurately aligned and bonded, avoiding defects caused by the bombardment of the overall structure by the subsequent etching process. Through this method, the process flow is simpler and easier to implement, which improves the performance and reliability of the sensor.

[0008] In view of claim 1, the present invention realizes a complete pressure sensor manufacturing technology through structural composition, and the SOI substrate is prepared to provide an SOI substrate as the basis of the device layer. The Wheatstone bridge piezoresistance is formed by forming a Wheatstone bridge piezoresistance on the SOI substrate by ion implantation and other methods to detect pressure changes. The Contact layer is formed into a film, and the Contact layer is deposited on the SOI substrate for subsequent contact hole production. The Contact hole is etched to form a contact hole on the Contact layer by photolithography and dry etching techniques. The metal conductive material is formed into a film and etched to deposit a metal conductive material in the contact hole, and a metal conductive path is formed by photolithography and etching techniques. The vacuum cavity groove is etched to etch a vacuum cavity groove on the SOI substrate to form a vacuum cavity. The SOI substrate is bonded to the second substrate, and the SOI substrate is bonded to the second substrate to form a sealed vacuum cavity. The TSV hole is filled with a conductive material, and a TSV hole is pre-formed on the second substrate and filled with a conductive material to ensure the reliability of the electrical connection. The TSV organic material filling and pad etching are to fill the TSV hole with organic material and etch out the pad for external connection. The SOI substrate backside etching is to etch from the backside of the SOI substrate to form an opening to release the thin film structure.

[0009] Preferably, with respect to claim 2 and claim 3, the back side of the silicon wafer is anisotropically etched by dry or wet method, so that a strain film structure with a thickness of micrometers is formed at the bottom of the local village. The etched silicon wafer is anodically bonded to the glass to form a sealed cavity. Through anisotropic etching, the thickness of the strain film can be accurately controlled to ensure the uniformity and consistency of the film structure. The formation of a thinner strain film can better respond to changes in external pressure and improve the sensitivity of the sensor. Anodic bonding technology can achieve high-quality sealing, prevent the influence of the external environment on the performance of the sensor, and improve the long-term stability of the sensor.

[0010] TSV holes are pre-formed on the second substrate to ensure accurate alignment before bonding. This avoids defects caused by the subsequent etching process bombarding the overall structure. With this method, the process flow is simpler and easier to implement, improving the performance and reliability of the sensor.

[0011] Forming TSV holes in advance can be precisely aligned before bonding, ensuring that the TSV holes are accurately aligned with the corresponding structures on the SOI substrate, improving the success rate and quality of bonding. It can avoid bombardment of the overall structure by subsequent etching processes, reduce defects caused by uneven or excessive etching, and improve the reliability and yield of the sensor. In addition, forming TSV holes in advance can simplify subsequent manufacturing steps, reduce process complexity, and improve production efficiency. By precisely aligning and reducing defects, the overall performance of the sensor, including sensitivity, linearity, and dynamic response characteristics, can be improved.

[0012] With respect to claim 4, two silicon wafers are used, one of which is used as the device layer and the other as the substrate. The substrate is thermally oxidized to form a layer of silicon dioxide, which serves as an insulating layer to isolate the device layer and the substrate. A cavity is made on the substrate by etching technology to form a vacuum cavity structure. The silicon wafer of the device layer is bonded to the substrate with the cavity to form a sealed vacuum cavity. The structure of the SOI silicon wafer is formed by thinning the thickness of the device layer to the required strain film thickness. Using two silicon wafers as the device layer and substrate respectively can better control the thickness and structure of each layer, thereby improving the stability and reliability of the overall structure. The structure of the SOI silicon wafer can reduce parasitic capacitance, improve the signal quality and stability of the sensor, and is suitable for high-precision measurement applications.

[0013] Furthermore, with respect to claim 5, the sidewalls of the etched shallow grooves are protected to prevent the sidewalls from being eroded during the subsequent isotropic etching process. After protecting the sidewalls, isotropic etching is performed to generate interconnected cavities. Isotropic etching can evenly erode silicon materials to form the desired cavity structure. A sealed cavity is formed on a substrate by epitaxial single crystal silicon or polycrystalline silicon. Epitaxial growth technology can ensure that the generated silicon layer has good crystal quality and uniformity. Finally, mechanical polishing is used to make the surface of the silicon substrate smooth, thereby improving the overall quality and reliability of the sensor.

[0014] The Wheatstone bridge piezoresistor is manufactured on the surface of a wafer by ion implantation or other methods. The local thinning of the strain film structure is set as a cross beam structure to further improve the sensitivity of the device.

[0015] Preferably, with respect to claim 8, the strain membrane structure is locally thinned, and a thinning process is performed in a local area of ​​the strain membrane structure to form a cross-beam structure. The cross-beam structure refers to a cross-shaped thin area formed at the center of the strain membrane, so that stress is concentrated in the area. By setting the cross-beam structure, stress can be concentrated in the cross-beam area, thereby improving the response sensitivity of the strain membrane to pressure changes.

[0016] Furthermore, local thinning of the cross-beam structure on the strain membrane can significantly improve the sensitivity, linearity and dynamic response characteristics of the MEMS pressure sensor. This method not only improves the performance of the sensor, but also enhances the rigidity and reliability of the structure, making it suitable for high-precision measurement applications.

[0017] The packaging structure formed by the manufacturing method can effectively prevent external shock and vibration from damaging the internal structure of the sensor, especially the film and the cross beam structure. It not only improves the durability of the sensor, but also simplifies the installation process of the sensor and reduces maintenance costs.

[0018] The above technical solution can achieve the following beneficial effects:

[0019] Compared with the prior art, the present invention has the following advantages and positive effects:

[0020] (1) The pressure sensor chip manufacturing technology provided by the present invention, through the improved cross-beam structure design, concentrates the stress in the cross-beam area, significantly improving the response sensitivity of the strain film to pressure changes. Setting up the cross-beam structure can significantly improve the sensor's response to tiny pressure changes and improve measurement accuracy.

[0021] (2) The pressure sensor chip manufacturing technology provided by the present invention forms TSV holes in advance through the second substrate, which can be accurately aligned before bonding to avoid defects caused by the subsequent etching process bombarding the overall structure. The method simplifies the manufacturing steps, reduces the process complexity, and improves production efficiency and yield rate.

[0022] (3) The pressure sensor chip manufacturing technology provided by the present invention adopts the design of forming TSV holes in advance to ensure accurate alignment before bonding, improve the success rate and quality of bonding, and reduce bonding defects. The back of the silicon wafer is anisotropically etched using dry or wet methods to form a precise strain film structure, and a high-quality sealed cavity is formed through anodic bonding technology to prevent the external environment from affecting the performance of the sensor.

[0023] (4) The pressure sensor chip manufacturing technology provided by the present invention adopts a cross-beam structure to increase the overall rigidity of the structure, reduce the error caused by external vibration or impact, and improve the reliability and stability of the sensor. The packaging structure can effectively prevent external impact and vibration from damaging the internal structure of the sensor, especially for the film and cross-beam structure, thereby improving the durability of the sensor.

[0024] (5) The pressure sensor chip manufacturing technology provided by the present invention finally makes the surface of the silicon substrate flat through mechanical polishing, reduces the surface roughness, and improves the surface quality and packaging effect of the sensor. The high-quality sealing and surface treatment technology of the sealed cavity ensures that the sensor maintains stable performance during long-term use and extends its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0026] Figure 1 It is a schematic diagram of the structural model of the MEMS pressure sensor with TSV holes formed in advance according to the present invention.

[0027] Figure 2 It is a flow chart of steps 1 to 2 in the method for manufacturing a MEMS pressure sensor in which a TSV hole is formed in advance according to the present invention.

[0028] Figure 3 This is a flow chart of steps three to four in the method for manufacturing a MEMS pressure sensor in which a TSV hole is formed in advance according to the present invention.

[0029] Figure 4 It is a flow chart of steps five to six in the method for manufacturing a MEMS pressure sensor in which a TSV hole is formed in advance according to the present invention.

[0030] Figure 5 This is a process flow chart of step seven in the method for manufacturing a MEMS pressure sensor in which a TSV hole is formed in advance according to the present invention.

[0031] Figure 6 It is a process flow chart of step eight in the method for manufacturing a MEMS pressure sensor in which a TSV hole is formed in advance according to the present invention.

[0032] Figure 7 It is a process flow chart of step nine in the method for manufacturing a MEMS pressure sensor in which a TSV hole is formed in advance according to the present invention.

[0033] Figure 8 It is a process flow chart of step 10 in the method for manufacturing a MEMS pressure sensor in which a TSV hole is formed in advance according to the present invention.

[0034] In the figure: (1) SOI silicon substrate, (2) top silicon, (3) piezoresistors, (4) contact layers, (5) electrical contact metal pillars, (6) SOI silicon substrate with vacuum cavity, (7) TSV hole filling material, (8) pad, and (9) organic epoxy insulating packaging layer. DETAILED DESCRIPTION

[0035] The present invention is further explained below with reference to the accompanying drawings and specific embodiments.

[0036] The embodiments of the present invention relate to a MEMS pressure sensor with TSV holes formed in advance and a manufacturing method thereof, such as Figure 1 As shown, the MEMS pressure sensor structure includes the following components: SOI silicon substrate 1, top silicon 2, piezoresistors 3, Contact layer 4, electrical contact metal pillars 5, SOI silicon substrate with vacuum cavity 6, TSV hole filling material 7, pad 8, organic epoxy insulating packaging layer 9. The SOI silicon substrate 1 serves as the basis of the device layer. The top silicon 2 is the top silicon layer of the SOI substrate. The piezoresistors 3 are varistor used to detect pressure changes. The Contact layer 4 is used for the subsequent production of contact holes. The electrical contact metal pillars 5 are used for electrical connection. The SOI silicon substrate 6 with vacuum cavity forms a sealed vacuum cavity. The TSV hole filling material 7 is used for electrical connection of the TSV hole. The pad 8 is used for external connection. The organic epoxy insulating packaging layer 9 is used to protect the sensor.

[0037] like Figure 2 As shown in the flowchart of steps 1 to 2, an SOI substrate 1 is provided, and a SOI substrate 1 is prepared, wherein the SOI substrate includes a top silicon layer, a buried oxide layer, and a bottom silicon layer. A Wheatstone bridge piezoresistor 2 is formed, and a piezoresistive region is defined using photolithography. Ion implantation is performed to form a varistor. The implanted ions are activated by an annealing process to form a stable piezoresistor.

[0038] The working principle of the MEMS pressure sensor includes key steps such as the formation of the Wheatstone bridge structure, the change of the piezoresistive resistance, signal amplification and processing, and finally converts the pressure into an electrical signal. The process is that the external pressure is sensed to the sensor, and the pressure causes the sensor diaphragm to deform. The deformation of the diaphragm transmits the stress to the piezoresistive element. Furthermore, the piezoresistive element changes its resistance value due to the stress. The change in resistance is converted into a voltage signal through the Wheatstone bridge circuit. Furthermore, the signal is amplified and filtered, the voltage signal is amplified, and unnecessary noise is filtered out. The signal range is checked, and if it is within the normal working range, the processed analog voltage signal is converted into a digital signal. The digital signal is further processed to display the pressure value.

[0039] like Figure 3As shown, the specific process of steps three to four is as follows. Form the Contact layer 3, and use plasma enhanced chemical vapor deposition or other deposition techniques to deposit a layer of insulating material, such as silicon dioxide. Form contact holes on the insulating layer by photolithography and dry etching techniques. Contact hole etching, form contact holes on the Contact layer 3 by photolithography and dry etching techniques to facilitate subsequent filling of metal conductive materials. Furthermore, the position and size of the contact holes and metal conductive paths can be accurately defined by photolithography technology to ensure the performance and reliability of the device. And dry etching technology can achieve high-precision etching to ensure that the shape and size of the contact holes and vacuum cavity grooves meet the design requirements.

[0040] Further, such as Figure 4 As shown, the specific process of steps five to six is ​​as follows: film formation and etching of metal conductive materials, using physical vapor deposition (PVD) or chemical vapor deposition (CVD) technology to deposit metal layers, such as aluminum or copper. The metal layer is deposited by PVD or CVD technology to ensure the continuity and reliability of the metal conductive path and avoid the problem of poor electrical connection. The insulating layer is deposited using PECVD or other deposition technology to ensure the uniformity and thickness of the insulating layer and improve the electrical insulation performance of the device. The metal conductive path is formed by photolithography and dry etching technology.

[0041] The vacuum cavity groove is formed on the SOI substrate 5, and the back of the silicon wafer is anisotropically etched using a dry or wet method to form a strained film structure with a thickness of several microns to tens of microns. The vacuum cavity groove is etched on the SOI substrate by photolithography and dry etching technology. Multi-step photolithography and etching: Through multi-step photolithography and etching technology, precise control of each step is ensured, which simplifies the overall manufacturing process and improves production efficiency and yield rate.

[0042] like Figure 5 As shown, the specific process of step seven is as follows: SOI substrate 1 and second substrate 4 are bonded to form a vacuum cavity, and TSV holes are pre-formed on second substrate 4. SOI substrate 1 and second substrate 4 are bonded using anodic bonding technology to form a high-quality sealed cavity. TSV holes are formed in advance and pre-formed on second substrate 4 to ensure precise alignment before bonding to avoid defects caused by subsequent etching processes bombarding the overall structure. This method simplifies the process flow and improves the performance and reliability of the sensor.

[0043] like Figure 6As shown, the specific process of step eight is as follows: TSV hole is filled with conductive material 6, and the conductive material is filled in the TSV hole using electroplating or chemical vapor deposition technology. Conductive materials, such as copper, are filled in the TSV hole using electroplating technology. During the electroplating process, it is necessary to ensure that the composition of the plating solution and the plating conditions (such as current density, temperature, time, etc.) meet the requirements to ensure uniform filling of the conductive material and good conductivity. Conductive materials, such as tungsten, are filled in the TSV hole using CVD technology. During the CVD process, parameters such as gas flow, temperature and pressure need to be controlled to ensure uniform deposition of the conductive material and good conductivity. Both technologies can ensure uniform filling of the conductive material in the TSV hole, avoid voids or unevenness, and improve the performance of the sensor.

[0044] like Figure 7 As shown, the specific process of step nine is as follows: TSV organic material fills 6 and pad8 is etched, and pad8 is etched by photolithography and dry etching technology. The position of pad8 is defined by photolithography technology. The pattern of pad8 is formed by coating, exposing and developing photoresist. Pad8 is etched by dry etching technology (such as reactive ion etching RIE). The etching time and power need to be controlled during the etching process to ensure that the shape and size of pad8 meet the design requirements.

[0045] like Figure 8 As shown, the specific process of step ten is as follows: an opening is etched on the back of the SOI substrate 1, and an anisotropic etching is performed on the back of the SOI substrate 1 using a dry method or a wet method. Anisotropic etching can ensure the verticality and flatness of the opening, avoid unnecessary damage, and improve the long-term reliability of the sensor. The required opening is formed, and the size and position of the opening are accurately controlled by photolithography and dry etching technology.

[0046] Improved cross-beam structure design, thinning is performed in the local area of ​​the strain film structure to form a cross-beam structure. Use photolithography technology to define the cross-beam area. Use dry etching technology to etch a cross-shaped thin area on the strain film. Through the coating, exposure and development of photoresist, the pattern of the cross beam is formed. Use dry etching technology (such as reactive ion etching RIE) to etch a cross-shaped thin area on the strain film. During the etching process, the etching depth and shape need to be precisely controlled to ensure the uniformity and consistency of the cross-beam structure.

[0047] Furthermore, the cross-beam structure concentrates stress in the cross-beam area, improving the response sensitivity of the strain film to pressure changes. The cross-beam structure not only improves the sensitivity, but also enhances the overall stiffness of the structure, improving the linearity and dynamic response characteristics of the sensor.

[0048] Use multi-layer composite films to combine the characteristics of different materials to achieve a wider operating temperature range and higher chemical stability. Deposit multi-layer films such as silicon nitride and silicon dioxide on the strained film. Ensure the uniformity and stability of the film by optimizing the deposition parameters. Commonly used materials for depositing multi-layer films on strained films include silicon nitride (SiN) and silicon dioxide (SiO2).

[0049] Furthermore, these materials have different physical and chemical properties and can be used in combination to optimize the performance of the sensor. By optimizing the deposition parameters (such as temperature, pressure, gas flow, etc.), the uniformity and stability of the film are ensured. Common deposition techniques include plasma enhanced chemical vapor deposition (PECVD) and low pressure chemical vapor deposition (LPCVD). Multilayer composite films can improve the stability and reliability of sensors at different temperatures and extend their operating temperature range.

[0050] The packaging structure produced in step 10 effectively prevents external shock and vibration from damaging the internal structure of the sensor. Mechanical polishing technology is used to make the surface of the silicon substrate flat to ensure the packaging of the sensor. Furthermore, mechanical polishing is used to make the surface of the silicon substrate flat, reduce surface roughness, and improve the surface quality and packaging effect of the sensor. The high-quality sealing and surface treatment technology of the sealed cavity ensures that the sensor maintains stable performance during long-term use and extends its service life.

[0051] The above-mentioned configuration can also be set in other embodiments, and the scope of protection of the present invention includes but is not limited to the situations listed in this embodiment. Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention, so the scope of protection of the present invention shall be subject to the scope defined by the claims.

[0052] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. The present invention provides a method for manufacturing a MEMS pressure sensor with a TSV hole formed in advance, and the process method mainly includes the following steps: 1) Providing an SOI substrate; 2) Forming a Wheatstone bridge piezoresistance; 3) Film forming contact layer; 4) Contact hole etching; 5) Film formation and etching of metal conductive materials; 6) Etching of vacuum cavity grooves on SOI substrate; 7) The SOI substrate and the second substrate are bonded to form a vacuum chamber; 8) Filling the TSV holes with conductive materials; 9)TSV organic material filling and pad etching; 10) An opening is etched on the back side of the SOI substrate.

2. The MEMS pressure sensor according to claim 1, characterized in that The method for forming the vacuum cavity groove includes performing anisotropic etching on the back of a silicon wafer using a dry method or a wet method, so that a strained film structure with a thickness of several microns to tens of microns is formed on the local bottom of the village, and the etched silicon wafer is anodically bonded to glass to form a sealed cavity.

3. The method for manufacturing a pressure sensor according to claim 1, characterized in that: The second substrate forms TSV holes in advance, which can be accurately aligned and bonded to avoid defects caused by the bombardment of the overall structure by the subsequent etching process. In this way, the process is simpler and easier to implement, improving the performance and reliability of the sensor.

4. The method for manufacturing a MEMS pressure sensor according to claim 1, characterized in that: The sensor uses two silicon wafers, one of which is used as a device layer and the other as a substrate; the substrate is thermally oxidized to form a layer of silicon dioxide; a cavity is made on the substrate by etching; the silicon wafer of the device layer is bonded to the substrate with the cavity; and a structure similar to an SOI silicon wafer and a sealed cavity are formed by thinning the thickness of the device layer to the required strain film.

5. The method for manufacturing a MEMS pressure sensor according to claim 1, characterized in that: The sensor etches shallow grooves on a silicon substrate by anisotropic etching; after protecting the sidewalls of the shallow grooves, isotropic etching is performed to generate interconnected cavities; a sealed cavity is formed on the substrate by epitaxial single crystal silicon or polycrystalline silicon; and finally the surface of the silicon substrate is flattened by mechanical polishing.

6. The method for manufacturing a pressure sensor according to claim 1, characterized in that: The Wheatstone bridge piezoresistor is manufactured on the surface of a wafer by methods such as ion implantation.

7. The method for manufacturing a MEMS pressure sensor according to claim 1, characterized in that: The local thinning of the strain film structure is set as a cross beam structure to further improve the sensitivity of the device.

8. The method for manufacturing a MEMS pressure sensor according to claim 1, characterized in that: The sensor adopts a multi-layer composite film and combines the characteristics of different materials to achieve a wider operating temperature range and higher chemical stability.

9. The method for manufacturing a MEMS pressure sensor according to claim 1, characterized in that The packaging structure formed by the manufacturing method can effectively prevent external shock and vibration from damaging the internal structure of the sensor, especially the film and the cross beam structure, which not only improves the durability of the sensor, but also simplifies the installation process of the sensor and reduces the maintenance cost.

Images