Production method for flip-chip pressure sensor for back pressure

Abstract

A production method for a flip-chip pressure sensor for back pressure, the flip-chip pressure sensor for back pressure comprising a main chip portion (1) and a cover plate portion (2), wherein a Wheatstone bridge (12) and a first electrical connection structure (13) are provided on a main body (11) of the main chip portion (1), the first electrical connection structure (13) being electrically connected to the Wheatstone bridge (12); and the cover plate portion (2) comprises a cover plate (21) and a second electrical connection structure (22), the cover plate (21) being bonded to the main body (11), and realizing electrical connection between the second electrical connection structure (22) and the first electrical connection structure (13). The second electrical connection structure (22) passes through the cover plate (21) and extends to the side surface of the cover plate (21) facing away from the main body (11), enabling direct soldering packaging of the second electrical connection structure (22) and an external substrate by means of SMT, and thereby facilitating packaging, improving the packaging efficiency and reliability of the flip-chip pressure sensor for back pressure.

Description

Manufacturing method of inverted back pressure sensor

[0001] This application claims priority to Chinese Patent Application No. 2024114589509, filed on October 18, 2024, entitled “Inverted Back Pressure Sensor and Manufacturing Method Thereof”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of sensor technology, and in particular to a method for manufacturing an inverted back-pressure sensor. Background Technology

[0003] Currently, pressure sensors used for measuring low pressure generally fall into two structural forms: one is front-facing pressure sensors, which require bonding and encapsulation. Both the bonding wires and the adhesive need to be in contact with the measured medium. Due to the alternating pressure, the bonding wires are prone to breakage and failure during use, and the encapsulation also needs to be in contact with different detection media, making it unsuitable for invasive media. The other type is the standard back-facing pressure sensor, which uses adhesive bonding or eutectic bonding for encapsulation. In this type, the circuit surface and bonding wires of the encapsulation structure do not contact the detection medium. However, adhesive bonding and eutectic bonding are prone to peeling from the substrate, especially in high-vibration scenarios, such as excavators. This results in high usage risks for existing standard back-facing pressure sensors, and requires very high reliability in the encapsulation adhesive, eutectic material, and eutectic bonding process, further limiting the application of standard back-facing pressure sensor structures. Summary of the Invention

[0004] The purpose of this disclosure is to solve the problems of reliability, complex packaging process, and low packaging efficiency of front-pressure sensors and ordinary back-pressure sensors.

[0005] To address the aforementioned technical problems, this disclosure provides a method for manufacturing a flip-chip back-pressure sensor. The flip-chip back-pressure sensor includes a main chip portion and a cover plate portion. The main chip portion includes a body, a Wheatstone bridge, and a first electrical connection structure. A diaphragm is formed on the body, and the Wheatstone bridge is disposed on the diaphragm. One end of the first electrical connection structure is connected to the Wheatstone bridge, and the other end extends to the outside of the diaphragm. The cover plate portion includes a cover plate and a second electrical connection structure. The cover plate is bonded to the body as a single unit, and a vacuum cavity is constructed on the side of the diaphragm near the cover plate. The second electrical connection structure penetrates the cover plate, with one end electrically connected to the first electrical connection structure and the other end located on the surface of the cover plate opposite to the body, allowing the second electrical connection structure to be directly soldered and packaged to an external substrate via SMT (Surface Mount Technology).

[0006] The manufacturing method of the inverted back-mounted pressure sensor includes the following steps:

[0007] A10: Take a wafer and set a Wheatstone bridge on one side of the wafer;

[0008] A20: A first bonding element and a first electrical connection structure connected to a Wheatstone bridge are provided on one side of the wafer after the processing in step A10.

[0009] A30: Take a silicon wafer or glass sheet and make a through hole through the silicon wafer or glass sheet;

[0010] A40: A conductive filling layer is provided in the through-hole of the silicon wafer or glass sheet after the processing in step A30, and a second bonding element and a conductive bonding layer are provided on one side thereon.

[0011] A50: A photolithographic groove is formed on the side of the silicon wafer or glass sheet that has been processed in step A40, where the second bonding element is located.

[0012] A60: The wafer processed in step A20 is bonded to the silicon wafer or glass sheet processed in step A50 and then annealed to form a bonded crystal; wherein, the second bonding member is bonded to the first bonding member, the conductive filling layer is bonded to the first electrical connection structure, and the opening of the groove is sealed by the wafer with the first electrical connection structure to form a vacuum cavity.

[0013] A70: A pad connected to the conductive filling layer is formed on the surface of the bonded crystal; the pad is located on the side of the conductive filling layer away from the conductive bonding layer, and the pad, the conductive filling layer and the conductive bonding layer constitute a second electrical connection structure.

[0014] A80: A pressure chamber is formed on the side of the bonded crystal away from the pad; a diaphragm is formed between the pressure chamber and the vacuum chamber;

[0015] A90: Plating solder balls on the bonding pads of the bonded crystal;

[0016] A100: The bonded crystal with solder balls is cut into pieces to form a flip-chip back-mounted pressure sensor.

[0017] A method for manufacturing a flip-chip back-pressure sensor, wherein the flip-chip back-pressure sensor includes a main chip portion and a cover plate portion. The main chip portion includes a body, a Wheatstone bridge, and a first electrical connection structure. A diaphragm is formed on the body, and the Wheatstone bridge is disposed on the diaphragm. One end of the first electrical connection structure is connected to the Wheatstone bridge, and the other end extends to the outside of the diaphragm. The cover plate portion includes a cover plate and a second electrical connection structure. The cover plate is bonded to the body as a single unit, and a vacuum cavity is constructed on the side of the diaphragm near the cover plate. The second electrical connection structure penetrates the cover plate, and one end is electrically connected to the first electrical connection structure, while the other end is located on the surface of the cover plate opposite to the body, allowing the second electrical connection structure to be directly soldered and packaged to an external substrate via SMT. The method for manufacturing the flip-chip back-pressure sensor includes the following steps:

[0018] B10: Take a wafer and set a Wheatstone bridge on one side of the wafer;

[0019] B20: A first electrical connection structure connected to a Wheatstone bridge is provided on one side of the wafer after the processing in step B10.

[0020] B30: Take a silicon wafer or glass sheet and make a through hole through the silicon wafer or glass sheet;

[0021] B40: Photolithographically etched grooves on one side of the silicon wafer or glass sheet after step B30;

[0022] B50: The wafer processed in step B20 is bonded to the silicon wafer or glass sheet processed in step B40 and then annealed to form a bonded crystal; wherein the opening of the groove is sealed by the wafer with the first electrical connection structure to form a vacuum cavity.

[0023] B60: A conductive filler layer is provided inside the through hole;

[0024] B70: An insulating layer is formed on the surface of the bonded crystal, and a pad is formed that is connected to the conductive filling layer; the pad is located on the side of the conductive filling layer away from the conductive bonding layer, and the pad, the conductive filling layer and the conductive bonding layer constitute a second electrical connection structure.

[0025] B80: A pressure-receiving cavity is formed on the side of the bonded crystal away from the pad; a diaphragm is formed between the pressure-receiving cavity and the vacuum cavity;

[0026] B90: Plating solder balls on the bonding pads of the bonded crystal;

[0027] B100: The bonded crystal with solder balls is cut into pieces to form a flip-chip back-mounted pressure sensor.

[0028] As can be seen from the above technical solution, the beneficial effects of this disclosure are as follows: The flip-chip back-pressure sensor of this application includes a main chip portion and a cover plate portion. The main chip portion has a Wheatstone bridge and a first electrical connection structure on its main body. The first electrical connection structure is electrically connected to the Wheatstone bridge. The cover plate portion includes a cover plate and a second electrical connection structure. The cover plate is bonded to the main body and realizes the electrical connection between the second electrical connection structure and the first electrical connection structure. The second electrical connection structure penetrates through the cover plate, and one end of the second electrical connection structure is electrically connected to the first electrical connection structure, while the other end is located on the side surface of the cover plate away from the main body. This allows the second electrical connection structure to be directly soldered and packaged with an external substrate via SMT, making the packaging convenient and simple, thereby improving the packaging efficiency and reliability of the flip-chip back-pressure sensor. Attached Figure Description

[0029] Figure 1 is a schematic diagram of the structure of an inverted back-pressure sensor in one embodiment.

[0030] Figure 2 is a schematic diagram of the main chip structure of the inverted back-pressure sensor shown in Figure 1.

[0031] Figure 3 is a schematic diagram of the cover plate structure of the inverted back-mounted pressure sensor shown in Figure 1.

[0032] Figure 4 is a schematic diagram of the process flow of steps A10-A20 in the production method of the inverted back-pressure sensor.

[0033] Figure 5 is a schematic diagram of the process flow of steps A30-A50 in the production method of the inverted back-pressure sensor.

[0034] Figure 6 is a schematic diagram of the process flow of steps A60-A80 in the production method of the inverted back-pressure sensor.

[0035] Figure 7 is a schematic diagram of an inverted back-pressure sensor obtained by manufacturing method 1, wherein the Wheatstone bridge is formed by an SOI structure.

[0036] Figure 8 is a schematic diagram of a flip-chip back-pressure sensor obtained by manufacturing method 1, wherein the Wheatstone bridge is formed by a PN junction and the diaphragm has islands.

[0037] Figure 9 is a schematic diagram of an inverted back-pressure sensor obtained by manufacturing method 1, wherein the Wheatstone bridge is formed by SOI structure and the diaphragm has islands.

[0038] Figure 10 is a schematic diagram of the process flow of steps B10-B20 in the second method for producing an inverted back-pressure sensor.

[0039] Figure 11 is a schematic diagram of the process flow of steps B30-B40 in the second method for producing an inverted back-pressure sensor.

[0040] Figure 12 is a schematic diagram of the process flow of steps B50-B80 in the second method for producing an inverted back-mounted pressure sensor.

[0041] Figure 13 is a schematic diagram of a flip-chip back-pressure sensor obtained by manufacturing method two, wherein the cover plate is formed by processing a silicon wafer.

[0042] Figure 14 is a schematic diagram of an inverted back-pressure sensor obtained by production method two, wherein the cover plate is formed by processing a glass sheet.

[0043] The reference numerals in the attached figures are explained as follows: 1-Main chip section; 11-Body body; 12-Wheatstone bridge; 121-Resistor strip; 122-Conductive line; 13-First electrical connection structure; 111-Diaphragm; 14-First bonding component; 15-Pressure chamber; 2-Cover plate section; 21-Cover plate; 22-Second electrical connection structure; 23-Vacuum chamber; 221-Conductive filling layer; 222-Welding layer; 223-Conductive bonding layer; 24-Second bonding component; 25-Groove. Detailed Implementation

[0044] Typical embodiments embodying the features and advantages of this disclosure will be described in detail in the following description. It should be understood that this disclosure can have various variations in different embodiments without departing from the scope of this disclosure, and the descriptions and illustrations therein are for illustrative purposes only and not intended to limit this disclosure.

[0045] In the description of this application, it should be understood that, in the embodiments shown in the accompanying drawings, the indications of direction or positional relationships (such as up, down, left, right, front, and back, etc.) are merely for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. These descriptions are appropriate when these elements are in the positions shown in the accompanying drawings. If the description of the positions of these elements changes, these directional indications also change accordingly.

[0046] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0047] When front-facing pressure sensors and ordinary back-facing pressure sensors are used in scenarios with significant vibration or different measurement media, pressure sensors suffer from issues such as reliability, complex packaging processes, and low packaging efficiency. This application designs a flip-chip back-facing pressure sensor that can be packaged using SMT technology. By directly soldering the SMT package, complex processes such as wire bonding are eliminated, effectively improving the packaging efficiency and reliability of the pressure sensor.

[0048] In the case of ordinary back-pressure sensors, fine metal wires are required during packaging. Heat, pressure, and ultrasonic energy are used to bond the metal wires to the substrate pads at multiple points. This process is called wire bonding.

[0049] SMT, or surface mount technology, is a circuit assembly technology that mounts leadless or short-lead surface-mount components onto the surface of a printed circuit board or other substrate, and then assembles them using methods such as reflow soldering or dip soldering. SMT packaging offers high reliability, strong vibration resistance, and a low solder joint defect rate.

[0050] Referring to Figure 1, the flip-chip back-pressure sensor of this application includes a main chip portion 1 and a cover portion 2. The cover portion 2 and the main chip portion 1 are fixed together by bonding methods such as eutectic bonding or metal thermoforming bonding. A pressure-sensing cavity 15 is provided on the side of the main chip portion 1 facing away from the cover portion 2. The pressure-sensing cavity 15 is used to contact the fluid whose pressure is to be detected. A pad is provided on the side of the cover portion 2 facing away from the main chip portion 1. The pad can be directly soldered to the substrate and packaged using SMT process to form a flip-chip back-pressure sensor.

[0051] Referring to Figure 2, the main chip part 1 includes a body 11, a Wheatstone bridge 12 and a first electrical connection structure 13. A diaphragm 111 is formed on the body 11, the Wheatstone bridge 12 is disposed on the diaphragm 111, one end of the first electrical connection structure 13 is connected to the Wheatstone bridge 12, and the other end extends to the outside of the diaphragm 111.

[0052] One side of the main body 11 is formed with a pressure-collecting cavity 15 through etching and photolithography processes. A diaphragm 111 is formed between the bottom of the pressure-collecting cavity 15 and the side of the main body 11 facing away from the pressure-collecting cavity 15. The pressure-collecting cavity 15 is used to contact the fluid whose pressure is to be detected. The diaphragm 111 is used to sense the fluid pressure entering the pressure-collecting cavity 15. For ease of description of the structure of the main body 11, this application defines the side of the main body 11 with the pressure-collecting cavity 15 as the bottom surface of the main body 11, and the side facing away from the pressure-collecting cavity 15 as the top surface of the main body 11.

[0053] A Wheatstone bridge 12 is formed on the top surface of the main body 11 by ion implantation. The Wheatstone bridge 12 includes resistance bars 121 and conductive wires 122. Four resistance bars 121 are arranged at intervals and are located on the side of the diaphragm 111 away from the pressure-applying cavity 15. Each pair of resistance bars 121 corresponds to the peak regions of tensile and compressive stresses of the diaphragm 111, respectively. The four resistance bars 121 are electrically connected to form the Wheatstone bridge 12.

[0054] When the diaphragm 111 undergoes elastic deformation under fluid pressure, the Wheatstone bridge 12 can generate a change in resistance value based on the elastic deformation, and then output a corresponding electrical signal according to the degree of elastic deformation. The pressure of the fluid can be determined based on the electrical signal output by the Wheatstone bridge 12.

[0055] In one embodiment, the four resistor strips 121 are formed via a PN junction or an SOI structure. A PN junction is formed by fabricating P-type and N-type semiconductors on the same semiconductor substrate (usually silicon or germanium) through processes such as epitaxy, dopant diffusion, or ion implantation. The boundary or interface between these two semiconductor materials is called a PN junction. SOI stands for Silicon-On-Insulator, a technology that introduces a buried oxide layer between the top silicon layer and the back substrate.

[0056] The first electrical connection structure 13 is deposited on the main body 11 through deposition and photolithography processes, and is located on the same side of the main body 11 as the Wheatstone bridge 12. One end of the first electrical connection structure 13 is connected to the conductive line 122 of the Wheatstone bridge 12, and the other end is connected to the second electrical connection structure 22 on the cover plate portion 2. Therefore, the Wheatstone bridge 12 is connected to the circuit on the substrate through the first electrical connection structure 13 and the second electrical connection structure 22. Four first electrical connection structures 13 are provided, and the four first electrical connection structures 13 are spaced apart.

[0057] In one embodiment, a silicon oxide layer is formed on the surface of the body 11 by a thermal oxidation process. The silicon oxide layer is an insulating structure that provides excellent insulation between the Wheatstone bridge 12 and the outside environment.

[0058] In one embodiment, silicon nitride is deposited on the top surface of the body 11 to form a silicon nitride layer. The silicon oxide layer and the silicon nitride layer form a passivation layer. The passivation layer effectively protects the diaphragm 111 and the Wheatstone bridge 12 and forms stress matching for the diaphragm 111.

[0059] The pressure-sensing diaphragm 111 is etched according to the range requirements, and the internal stress of the diaphragm 111 is balanced by matching the thickness of the passivation layer. The internal stress includes tensile stress and compressive stress.

[0060] In one embodiment, the main chip portion 1 further includes a first bonding member 14, which is used for bonding to the cover portion 2. The first bonding member 14 is annular and is disposed on the top surface of the main body 11, located outside the Wheatstone bridge 12 and the first electrical connection structure 13. The first bonding member 14 is a metal component or a semiconductor component. Specifically, the first bonding member 14 is formed by photolithographically etching lead holes on the top surface of the main body 11, depositing a metal layer, and then photolithographically etching the metal layer.

[0061] The cover plate portion 2 includes a cover plate 21 and a second electrical connection structure 22. The cover plate 21 can be formed by processing a silicon wafer or a glass sheet. A groove 25 is photolithographically formed on one side of the cover plate 21, and the side with the groove 25 is bonded to the top surface of the main body 11, so that the main body 11 seals the opening end of the groove 25 to form a closed vacuum cavity 23. The position of the diaphragm 111 corresponds to the position of the groove 25, so that the vacuum cavity 23 becomes the elastic deformation space when the diaphragm 111 undergoes elastic deformation. For ease of description of the structure of the main body 11, this application defines the side of the cover plate 21 with the groove 25 as the bottom surface of the cover plate 21, and the side away from the groove 25 as the top surface of the cover plate 21. The second electrical connection structure 22 penetrates the bottom surface and the top surface of the cover plate 21, so that the second electrical connection structure 22 connects the substrate and the first electrical connection structure 13.

[0062] Referring to Figure 3, the cover plate portion 2 also includes a second bonding member 24. The second bonding member 24 is disposed on the side of the cover plate 21 facing the main body 11 and corresponds to the position of the first bonding member 14. The second bonding member 24 is bonded to the first bonding member 14 to realize the bonding connection between the cover plate portion 2 and the main chip portion 1. The second bonding member 24 is annular and located outside the second electrical connection structure 22. The first bonding member 14 and the second bonding member 24 are metal parts or semiconductor parts. Specifically, the second bonding member 24 is formed by photolithographically etching lead holes on the bottom surface of the cover plate 21, depositing a metal layer, and then photolithographically etching the metal layer.

[0063] In embodiments where the second bonding member 24 is bonded to the first bonding member 14, the second electrical connection structure 22 and the first electrical connection structure 13 can be connected by bonding. Specifically, during the bonding process between the second bonding member 24 and the first bonding member 14, the bonding connection between the second electrical connection structure 22 and the first electrical connection structure 13 is simultaneously completed. A eutectic bond is formed between the second bonding member 24 and the first bonding member 14, and between the second electrical connection structure 22 and the first electrical connection structure 13, as shown in the flip-chip back-side pressure sensor in Figures 1 and 7 to 9.

[0064] When the cover plate 21 is a silicon wafer, a silicon oxide layer can be formed on the bottom surface of the cover plate 21 by oxidation to improve the insulation effect of the cover plate portion 2.

[0065] In one embodiment, the cover plate 21 is formed from a glass sheet. In this embodiment, the cover plate portion 2 does not have a second bonding member 24, and the main chip portion 1 does not have a first bonding member 14. The cover plate 21 is directly bonded to the main body 11, forming an anodic bond between the glass material and the silicon material. In this embodiment, the surface of the main body 11 may not have a silicon oxide layer and a silicon nitride layer; or a silicon oxide layer and a silicon nitride layer may only be provided above the Wheatstone bridge 12, while the position of the main body 11 used for bonding with the cover plate 21 does not have a silicon oxide layer and a silicon nitride layer, as shown in the flip-chip back pressure sensor in FIG14.

[0066] In one embodiment, the cover plate 21 is formed from a silicon wafer. In this embodiment, the cover plate portion 2 does not have a second bonding member 24, and the main chip portion 1 does not have a first bonding member 14. The cover plate 21 is directly bonded to the main body 11, forming a silicon-to-silicon bond between silicon materials. In this embodiment, a silicon oxide layer can be provided on the surface of the main body 11 and the surface of the cover plate 21 to improve the insulation effect of the flip-chip back-side pressure sensor. In one embodiment, a silicon oxide layer and a silicon nitride layer can be provided only above the Wheatstone bridge 12, while no silicon nitride layer is provided at the location of the main body 11 used for bonding with the cover plate 21, as shown in the flip-chip back-side pressure sensor in FIG13.

[0067] The cover plate 21 has a through hole photolithographically etched on it. The through hole connects the bottom surface and the top surface of the cover plate 21. The second electrical connection structure 22 is fixedly connected to the cover plate 21 and passes through the through hole, so that one end of the second electrical connection structure 22 is connected to the first electrical connection structure 13, and the other end forms a pad for direct soldering and packaging with the substrate via SMT.

[0068] There are four through holes, and the positions of the four holes correspond to the positions of the first electrical connection structure 13. Each through hole is provided with a second electrical connection structure 22, so that four second electrical connection structures 22 for connecting the substrate and the first electrical connection structure 13 are formed on the cover plate 21.

[0069] The second electrical connection structure 22 includes a conductive filler layer 221 and a solder layer 222. The conductive filler layer 221 is disposed within a through-hole, and the solder layer 222 is disposed on the side of the cover plate 21 opposite to the main body 11 and is electrically connected to the conductive filler layer 221. The solder layer 222 forms a pad and is used for SMT surface mount packaging with an external substrate. The conductive filler layer 221 can be formed within the through-hole by deposition or electroplating of a metal material. The solder layer 222 is formed on the top surface of the cover plate 21 by deposition and photolithography processes and is connected to the conductive filler layer 221.

[0070] In one embodiment, the second electrical connection structure 22 further includes a conductive bonding layer 223, which is disposed on the side of the conductive filler layer 221 opposite to the solder layer 222. One end of the conductive bonding layer 223 is electrically connected to the conductive filler layer 221, and the other end is bonded to the first electrical connection structure 13. The conductive bonding layer 223 can be formed by deposition and photolithography processes.

[0071] When manufacturing inverted back-mounted pressure sensors, production can be carried out by at least the following methods.

[0072] Method 1: Referring to Figures 4-6, first, a Wheatstone bridge 12 and a first electrical connection structure 13 are installed on the main body 11 (see Figure 4 for details), and a second electrical connection structure 22 and a groove 25 are installed on the cover plate 21 (see Figure 5 for details). Then, the two are bonded together, and the solder pads and pressure-sensing cavity 15 are machined (see Figure 6 for details). The specific steps of the production method for the flip-chip back-pressure sensor are as follows:

[0073] A10: Take a wafer and set a Wheatstone bridge 12 on one side of the wafer. In this step, the wafer can be a silicon wafer (as shown in Figures 1 and 8) or a silicon wafer with an internal oxide layer (as shown in Figures 7 and 9). The step of setting the Wheatstone bridge 12 on the wafer includes:

[0074] A11: A light boron region is photolithographically etched on the top surface of the wafer, and a resistor strip 121 is formed within the light boron region through ion implantation and annealing diffusion. Specifically, a light boron region is first photolithographically etched on the top surface of the wafer, and then the resistor strip 121 is formed through ion implantation and annealing diffusion.

[0075] A12: A boron-rich region is photolithographically etched on the top surface of the wafer where the resistor strip 121 is formed, and conductive lines 122 are formed within the boron-rich region through ion implantation and annealing diffusion processes. The conductive lines 122 are connected to the resistor strip 121 to form a Wheatstone bridge 12. Specifically, a boron-rich region is first photolithographically etched on the top surface of the wafer, and then conductive lines 122 are formed through ion implantation and annealing diffusion processes.

[0076] A20: A first bonding element 14 and a first electrical connection structure 13 connected to a Wheatstone bridge 12 are disposed on one side of the wafer after the processing in step A10. This step specifically includes:

[0077] A21: A second oxide layer is formed on the wafer on which the Wheatstone bridge 12 is formed, covering the Wheatstone bridge 12 and the wafer surface. Specifically, the wafer on which the Wheatstone bridge 12 is formed is oxidized using a thermal oxidation device to form an oxide layer on the surface of the wafer.

[0078] A22: A passivation layer is formed on the wafer with the second oxide layer by depositing silicon nitride. In this step, silicon nitride is deposited on the top surface of the wafer with the second oxide layer, such that the passivation layer covers the surface of the wafer on the side where the Wheatstone bridge 12 is located. The passivation layer protects the Wheatstone bridge 12 and provides stress matching for the subsequent formation of the film 111.

[0079] A23: Photolithographically pattern a first lead hole and a second lead hole on the top surface of the wafer with the passivation layer formed; the second lead hole is located outside the first lead hole.

[0080] A24: A metal layer is deposited on the top surface of the wafer after step A23. Then, photolithography is used to form the metal layer, creating a first electrical connection structure 13 within the first lead hole and a first bonding member 14 within the second lead hole. Specifically, during photolithography, the metal layer outside the locations of the first and second lead holes is removed, leaving the portion that forms the first electrical connection structure 13 and the first bonding member 14. The bottom surface of the first electrical connection structure 13 is connected to the conductive line 122, and the top surfaces of the first electrical connection structure 13 and the first bonding member 14 are exposed outside the passivation layer. The first electrical connection structure 13 can be a metal material such as aluminum, copper, gold, or tin, or a semiconductor material such as germanium or silicon. The first bonding member 14 can also be a metal material such as aluminum, copper, gold, or tin, or a semiconductor material such as germanium or silicon. Optionally, the material of the first bonding member 14 is the same as that of the first electrical connection structure 13, allowing the first bonding member 14 and the first electrical connection structure 13 to be formed simultaneously.

[0081] A30: Take another wafer and form through-holes on it. This wafer can be a silicon wafer or a glass sheet. For thicker wafers, first thin them to a set thickness; for example, in one embodiment of this application, the wafer needs to be thinned to 400µm. For wafers of suitable thickness, this step can be omitted. Then, photolithographically etch the through-holes onto the wafer, with the through-holes vertically positioned. That is, the through-holes can be formed using TSV or TGV processes. TSV stands for Through Silicon Via, a vertical interconnect via that penetrates a silicon wafer or chip. TGV stands for Through Glass Via, a vertical interconnect via that penetrates a glass substrate.

[0082] A40: A conductive filling layer 221 is disposed within the through-hole of the wafer after step A30, and a second bonding member 24 and a conductive bonding layer 223 are disposed on one side thereof. This step includes:

[0083] A41: A first oxide layer is formed on the inner wall and outer surface of the via of the wafer. In this step, the wafer with the via formed is subjected to an oxidation process using a thermal oxidation device, so that the first oxide layer is formed on the inner wall of the via and the surface of the wafer.

[0084] A42: An adhesion layer and a seed layer are sequentially formed within the via of a wafer with a first oxide layer through a deposition process. Prior to depositing the adhesion layer, an insulating layer, which can be made of silicon oxide, can be deposited on the inner wall of the via through a deposition process.

[0085] A43: A conductive filling layer 221 is formed in the through-hole of the wafer in which the seed layer is formed by electroplating. The conductive filling layer 221 is made of the same material as the seed layer. The conductive filling layer 221 can be a metal such as aluminum, copper, gold, or tin, or a semiconductor material such as germanium or silicon. In some embodiments, the electroplated conductive filling layer 221 is planarized by CMP treatment, where CMP refers to chemical mechanical polishing.

[0086] A44: An insulating layer is deposited on one end face of the wafer after step A43, and a third lead hole is photolithographically etched at the corresponding conductive fill layer, and a fourth lead hole is photolithographically etched on the outside of the conductive fill layer. The third lead hole is photolithographically etched onto the conductive fill layer.

[0087] A45: After processing in step A44, a metal layer is deposited on the bottom surface of one end of the wafer. Then, a conductive bonding layer 223 is formed at the third lead hole using photolithography, and a metal layer is formed at the fourth lead hole to create a second bonding element 24. The conductive bonding layer 223 is connected to the conductive filling layer 221. The conductive bonding layer 223 can be a metal material such as aluminum, copper, gold, or tin, or a semiconductor material such as germanium or silicon. The second bonding element 24 can also be a metal material such as aluminum, copper, gold, or tin, or a semiconductor material such as germanium or silicon. Optionally, the material of the second bonding element 24 is the same as that of the conductive bonding layer 223, so that the second bonding element 24 and the conductive bonding layer 223 can be processed and formed simultaneously.

[0088] A46: After step A45, an insulating layer is deposited on the end face of the wafer opposite to the conductive bonding layer 223 and the second bonding member 24, and a fifth lead hole is photolithographically etched at the corresponding conductive filling layer. The insulating layer can be silicon oxide or silicon nitride.

[0089] A50: A photolithographic groove 25 is formed on one side of the wafer processed in step A40, on which the second bonding member 24 is located. The groove 25 is located on the bottom surface of the wafer and is spaced apart from the conductive bonding layer 223.

[0090] A60: The wafer processed in step A20 is bonded to the wafer processed in step A50, and the stress at the bonding point is eliminated by an annealing process, fixing the two together to form a bonded crystal. In the bonding process, the second bonding element 24 is bonded to the first bonding element 14, the conductive filling layer 221 is bonded to the first electrical connection structure 13, and the groove 25 is sealed by the wafer with the first electrical connection structure 13 to form a vacuum cavity 23. The first bonding element 14 and the second bonding element 24 are bonded, achieving eutectic bonding between the main chip portion 1 and the cover plate portion 2.

[0091] A70: A pad connected to the conductive filling layer 221 is formed on the surface of the bonded crystal. The pad is located on the side of the conductive filling layer 221 away from the conductive bonding layer 223, i.e., on the top surface of the bonded crystal, and the pad, the conductive filling layer 221, and the conductive bonding layer 223 constitute a second electrical connection structure 22. Specifically, a metal layer is first formed at the fifth lead hole on the top surface of the bonded crystal through a deposition process, and then a solder layer 222 is formed at the fifth lead hole through photolithography, i.e., the pad is formed.

[0092] In other embodiments, step A46 can also be positioned between steps A60 and A70. That is, the wafer processed in step A20 is first bonded to the wafer processed in step A45, and then an insulating layer is deposited on the top surface of the bonded crystal, and a fifth lead hole is photolithographically formed. Next, a metal layer is deposited on the top surface of the bonded crystal, and the metal layer is photolithographically formed to create a solder layer at the fifth lead hole that connects to the conductive filler layer 221, thus forming a solder pad.

[0093] A80: A pressure-sensing cavity 15 is formed on the side of the bonded crystal away from the pads. Specifically, the pressure-sensing cavity 15 is formed on the bottom surface of the bonded crystal through etching and photolithography processes, creating a pressure-sensing diaphragm 111 between the pressure-sensing cavity 15 and the vacuum chamber 23. For bonded crystals with a large thickness, before processing the pressure-sensing cavity 15, the bottom surface of the bonded crystal is first photolithographically etched or polished to thin it, and then the pressure-sensing cavity 15 is photolithographically etched. For example, in one embodiment of this application, before etching and photolithographically etching the pressure-sensing cavity 15, the bottom surface of the bonded crystal is photolithographically etched or polished to thin it to a total thickness of 800 μm, meaning the wafer containing the Wheatstone bridge 12 is thinned to 400 μm. In other embodiments, other dimensions may also be used.

[0094] In one embodiment, the diaphragm 111 is thin-film, that is, the cross-section of the pressure-applying cavity 15 is C-shaped, as shown in Figures 1 and 7. In another embodiment, the diaphragm 111 has a larger thickness in the middle, that is, an island structure is formed in the pressure-applying cavity 15, as shown in Figures 8 and 9.

[0095] A90: Solder balls are placed on the bonding pads of the bonding crystal. The solder balls are used for soldering to the substrate.

[0096] A100: The bonded crystal with solder balls is cut into pieces to form a flip-chip back-mounted pressure sensor.

[0097] Method 2: Referring to Figures 10-12, first, a Wheatstone bridge 12 and a first electrical connection structure 13 are set on the main body 11 (see Figure 10 for details), and through holes and grooves 25 are set on the cover plate 21 (see Figure 11 for details). Then, the two are bonded together, and then the second electrical connection structure 22 and the pressure-applying cavity 15 are machined (see Figure 12 for details). The specific steps of the production method of the inverted back-mounted pressure sensor are as follows:

[0098] B10: Take a wafer and set a Wheatstone bridge 12 on one side of the wafer. In this step, the wafer can be a silicon wafer (as shown in Figure 13) or a silicon wafer with an internal oxide layer (as shown in Figure 14). The step of setting the Wheatstone bridge 12 on the wafer includes:

[0099] B11: A light boron region is photolithographically patterned on the top surface of the wafer, and a resistor strip 121 is formed within the light boron region through ion implantation and annealing diffusion. Specifically, a light boron region is first photolithographically patterned on the top surface of the wafer, and then the resistor strip 121 is formed through ion implantation and annealing diffusion.

[0100] B12: A boron-rich region is photolithographically formed on the top surface of the wafer where the resistor strip 121 is formed, and conductive lines 122 are formed by ion implantation and annealing diffusion. The conductive lines 122 are connected to the resistor strip 121 to form a Wheatstone bridge 12. Specifically, a boron-rich region is first photolithographically formed on the top surface of the wafer, and then conductive lines 122 are formed by ion implantation and annealing diffusion.

[0101] B20: A first electrical connection structure 13 connected to the Wheatstone bridge 12 is formed on one side of the wafer after step B10. In this step, a first lead hole is photolithographically etched on the top surface of the wafer forming the Wheatstone bridge 12, and a metal layer is deposited on the top surface of the wafer. Then, the metal layer is photolithographically etched to form the first electrical connection structure 13 within the first lead hole. The bottom surface of the first electrical connection structure 13 is connected to the conductive line 122. The first electrical connection structure 13 can be made of metal materials such as aluminum, copper, gold, or tin.

[0102] In an embodiment where the cover plate 21 is formed from a silicon wafer, between step B10 and step B20, a second oxide layer is further formed on the wafer where the Wheatstone bridge 12 is formed, covering the Wheatstone bridge 12 and the wafer surface. That is, the wafer where the Wheatstone bridge 12 is formed is first oxidized using a thermal oxidation device to form an oxide layer on the wafer surface, and then a first electrical connection structure 13 is formed on the top surface of the wafer through deposition and photolithography processes, with the top surface of the first electrical connection structure 13 exposed outside the oxide layer.

[0103] In one embodiment, after the step of forming a second oxide layer covering the Wheatstone bridge 12 and the wafer surface on the wafer to which the Wheatstone bridge 12 is formed, and before bonding with the cover plate, the method further includes: forming a silicon nitride layer on the wafer to which the second oxide layer is formed over the Wheatstone bridge 12 by deposition and photolithography processes, wherein the silicon nitride layer and the oxide layer form a passivation layer. The passivation layer protects the Wheatstone bridge 12 and provides stress matching for the subsequent formation of the film 111. In this embodiment, a silicon nitride layer is not provided at the location on the top surface of the wafer to which the Wheatstone bridge 12 is formed, where it is bonded to the cover plate; or neither a silicon nitride layer nor an oxide layer is provided at the location on the top surface of the wafer to which the Wheatstone bridge 12 is formed, where it is bonded to the cover plate.

[0104] In an embodiment where the cover plate 21 is formed from a glass sheet, no silicon nitride layer or oxide layer is provided on the top surface of the wafer where the Wheatstone bridge 12 is formed and at the location for bonding with the cover plate.

[0105] B30: Take another wafer and form through-holes on it. This wafer can be a silicon wafer or a glass sheet. For thicker wafers, first thin them to a predetermined thickness; for example, in one embodiment of this application, the wafer needs to be thinned to 400µm. For wafers of suitable thickness, this step can be omitted. Then, photolithographically etch the through-holes onto the wafer, with the through-holes vertically positioned. That is, the through-holes can be formed using TSV or TGV processes.

[0106] B40: A recess 25 is photolithographically etched on one side of the wafer after step B30. The recess 25 is located on the bottom surface of the wafer and is spaced apart from the via.

[0107] In an embodiment where the cover plate 21 is formed from a silicon wafer, an oxide layer is formed on the inner wall of the through hole and the outer surface of the wafer between steps B30 and B40.

[0108] B50: The wafer processed in step B20 and the wafer processed in step B40 are bonded to the wafer with the groove 25 formed, and the stress at the bonding point is eliminated by an annealing process, so that the two are fixed together to form a bonded crystal. The groove 25 is sealed by the wafer with the first electrical connection structure 13 to form a vacuum cavity 23. In this process, when the cover plate 21 is formed from a glass sheet, the bottom surface of the cover plate 21 is directly bonded to the top surface of the main body 11 to form an anodic bond between the glass material and the silicon material. When the cover plate 21 is formed from a silicon wafer, the bottom surface of the cover plate 21 is bonded to the top surface of the main body to form a silicon-silicon bond between silicon materials, or a silicon-silicon bond between silicon oxide materials.

[0109] B60: A conductive filling layer 221 is provided inside the through-hole. This step includes:

[0110] B61: An adhesion layer and a seed layer are sequentially formed within the through-hole using a deposition process. Before depositing the adhesion layer, an insulating layer, which can be made of silicon oxide, can be deposited on the inner wall of the through-hole using a deposition process.

[0111] B62: A conductive filler layer 221 is formed on a wafer with a seed layer through an electroplating process. The conductive filler layer 221 is made of the same material as the seed layer. The conductive filler layer 221 can be a metal such as aluminum, copper, gold, or tin.

[0112] B70: An insulating layer is formed on the surface of the bonded crystal, and pads are formed to connect with the conductive filling layer 221. This step specifically includes:

[0113] B71: An oxide layer is formed on the end face where the bonded crystal is connected to the conductive filler layer through an oxidation process. The oxide layer is used for insulation between the flip-chip back pressure sensor and the substrate, i.e., it serves as an insulating layer.

[0114] B72: Photolithographically print the fifth lead hole on the insulating layer of the wafer after step B71. The position of the fifth lead hole corresponds to the conductive filling layer 221, and the fifth lead hole completely penetrates the insulating layer formed in step B71.

[0115] B73: A bonding pad is formed at the fifth lead hole using deposition and photolithography. Specifically, a metal layer is first deposited on the top surface of the bonded crystal, and then the metal layer is photolithographically lithographically formed to create a bonding layer 222 at the fifth lead hole, thus forming the bonding pad.

[0116] B80: A pressure-sensing cavity 15 is formed on the side of the bonded crystal away from the pads. Specifically, the pressure-sensing cavity 15 is formed on the bottom surface of the bonded crystal through etching and photolithography processes, creating a pressure-sensing diaphragm 111 between the pressure-sensing cavity 15 and the vacuum chamber 23. For bonded crystals with a large thickness, before processing the pressure-sensing cavity 15, the bottom surface of the bonded crystal is first photolithographically etched or polished to thin it, and then the pressure-sensing cavity 15 is photolithographically etched. For example, in one embodiment of this application, before etching and photolithographically etching the pressure-sensing cavity 15, the bottom surface of the bonded crystal is photolithographically etched or polished to thin it to a total thickness of 800 μm, meaning the wafer containing the Wheatstone bridge 12 is thinned to 400 μm. In other embodiments, other dimensions may also be used.

[0117] In one embodiment, the diaphragm 111 is thin-film, that is, the cross-section of the pressure-applying cavity 15 is C-shaped, as shown in Figures 13 and 14. In another embodiment, the diaphragm 111 has a larger thickness in the middle, that is, an island structure is formed in the pressure-applying cavity 15.

[0118] B90: Solder balls are placed on the bonding pads of the bonding crystal. The solder balls are used for soldering to the substrate.

[0119] B100: The bonded crystal with solder balls is cut into pieces to form a flip-chip back-mounted pressure sensor.

[0120] The flip-chip back-pressure sensor of this application includes a main chip portion 1 and a cover portion 2. The main chip portion 1 has a Wheatstone bridge 12 and a first electrical connection structure 13 on its main body 11. The first electrical connection structure 13 is electrically connected to the Wheatstone bridge 12. The cover portion 2 includes a cover plate 21 and a second electrical connection structure 22. The cover plate 21 is bonded to the main body 11 and realizes the electrical connection between the second electrical connection structure 22 and the first electrical connection structure 13. The second electrical connection structure 22 penetrates the cover plate 21, and one end of the second electrical connection structure 22 is electrically connected to the first electrical connection structure 13, while the other end is located on the side surface of the cover plate 21 away from the main body 11. This allows the second electrical connection structure 22 to be directly soldered and packaged with an external substrate via SMT, which facilitates packaging and improves the packaging efficiency and reliability of the flip-chip back-pressure sensor.

[0121] Although this disclosure has been described with reference to several typical embodiments, it should be understood that the terminology used is descriptive and exemplary, and not restrictive. Because this disclosure can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A method for manufacturing an inverted back-pressure sensor, the inverted back-pressure sensor comprising: The main chip includes a body, a Wheatstone bridge, and a first electrical connection structure. A diaphragm is formed on the body, the Wheatstone bridge is disposed on the diaphragm, one end of the first electrical connection structure is connected to the Wheatstone bridge, and the other end extends to the outside of the diaphragm. The cover plate portion includes a cover plate and a second electrical connection structure. The cover plate is bonded to the main body as a whole, and a vacuum cavity is constructed on the side of the diaphragm near the cover plate. The second electrical connection structure penetrates the cover plate, and one end is electrically connected to the first electrical connection structure, while the other end is located on the surface of the cover plate away from the main body, so that the second electrical connection structure can be directly soldered and packaged with an external substrate by SMT. The cover plate has a groove on the side facing the main body, and the main body seals the opening end of the groove to form a closed vacuum cavity; the main body has a pressure-inducing cavity on the side away from the cover plate, and the diaphragm is formed between the pressure-inducing cavity and the vacuum cavity. The production method includes the following steps: A10: Take a wafer and set a Wheatstone bridge on one side of the wafer; A20: A first bonding element and a first electrical connection structure connected to a Wheatstone bridge are provided on one side of the wafer after the processing in step A10. A30: Take a silicon wafer or glass sheet and make a through hole through the silicon wafer or glass sheet; A40: A conductive filling layer is provided in the through-hole of the silicon wafer or glass sheet after the processing in step A30, and a second bonding element and a conductive bonding layer are provided on one side thereon. A50: A photolithographic groove is formed on the side of the silicon wafer or glass sheet that has been processed in step A40, where the second bonding element is located. A60: The wafer processed in step A20 is bonded to the silicon wafer or glass sheet processed in step A50 and then annealed to form a bonded crystal; wherein, the second bonding member is bonded to the first bonding member, the conductive filling layer is bonded to the first electrical connection structure, and the opening of the groove is sealed by the wafer with the first electrical connection structure to form a vacuum cavity. A70: A pad connected to the conductive filling layer is formed on the surface of the bonded crystal; the pad is located on the side of the conductive filling layer away from the conductive bonding layer, and the pad, the conductive filling layer and the conductive bonding layer constitute a second electrical connection structure. A80: A pressure chamber is formed on the side of the bonded crystal away from the pad; a diaphragm is formed between the pressure chamber and the vacuum chamber; A90: Plating solder balls on the bonding pads of the bonded crystal; A100: The bonded crystal with solder balls is cut into pieces to form a flip-chip back-mounted pressure sensor.

2. The method for manufacturing the inverted back-side pressure sensor according to claim 1, wherein, A10: The steps of taking a wafer and setting a Wheatstone bridge on one side of the wafer specifically include: A11: A light boron region is photolithographically patterned on one side of the wafer, and a resistor strip is formed in the light boron region by ion implantation and annealing diffusion process; A12: A boron-rich region is photolithographically formed on a wafer with resistor strips, and conductive lines are formed in the boron-rich region by ion implantation and annealing diffusion process; the conductive lines are connected to the resistor strips to form a Wheatstone bridge.

3. The method for manufacturing the inverted back-side pressure sensor according to claim 1, wherein, A20: The step of setting a first bonding element and a first electrical connection structure connected to a Wheatstone bridge on one side of the wafer after step A10 specifically includes: A21: Form a second oxide layer covering the Wheatstone bridge and the wafer surface on the wafer in which the Wheatstone bridge is formed; A22: A passivation layer is formed on a wafer with a second oxide layer by depositing silicon nitride; the passivation layer covers the surface of the wafer on the side where the Wheatstone bridge is located; A23: Photolithographically print the first and second lead holes on a wafer with a passivation layer. A24: The wafer processed in step A23 is deposited and photolithographically etched to form a first electrical connection structure in the first lead hole and a first bonding element in the second lead hole.

4. The method for manufacturing the inverted back-side pressure sensor according to claim 1, wherein, In step A30, before “forming a through-hole through the silicon wafer or glass sheet”, the silicon wafer or glass sheet is thinned to a set thickness.

5. The method for manufacturing the inverted back-side pressure sensor according to claim 1, wherein, A40: The step of setting a conductive filling layer in the through-hole of the silicon wafer or glass sheet after step A30 and setting a second bonding element and a conductive bonding layer on one side thereof, specifically including: A41: A first oxide layer is formed on the inner wall and outer surface of the through-hole of a silicon wafer or glass sheet; A42: An adhesion layer and a seed layer are sequentially formed in the through-hole of a silicon wafer or glass sheet with a first oxide layer formed by a deposition process; A43: A conductive filling layer is formed in the through-hole of a silicon wafer or glass sheet with a seed layer formed by electroplating. A44: Deposit an insulating layer on one end face of the silicon wafer or glass sheet after the process in step A43, and photolithographically etch a third lead hole at the corresponding conductive filling layer and a fourth lead hole on the outside of the conductive filling layer. A45: A conductive bonding layer is formed at the third lead hole on one end face of the silicon wafer or glass sheet after the processing in step A44 by deposition and photolithography, and a second bonding element is formed at the fourth lead hole by deposition and photolithography. A46: Deposit an insulating layer on one end face of the silicon wafer or glass sheet away from the conductive bonding layer and the second bonding element after step A45, and photolithographically etch a fifth lead hole at the corresponding conductive filling layer.

6. The method for manufacturing the inverted back-side pressure sensor according to claim 5, wherein, Before step "A42: Sequentially forming an adhesion layer and a seed layer within the via of a silicon wafer or glass sheet with a first oxide layer through a deposition process", the method further includes: An insulating layer is deposited on the inner wall of the through hole using a deposition process.

7. The method for manufacturing the inverted back-side pressure sensor according to claim 5, wherein, A70: The step of forming pads on the surface of a bonded crystal that are connected to a conductive filler layer, specifically including; A bonding pad is formed at the fifth lead hole of the bonded crystal through deposition and photolithography processes.

8. The method for manufacturing the inverted back-side pressure sensor according to claim 1, wherein, In step A80, before "forming a pressure chamber on the side of the bonding crystal away from the pad", the method further includes: performing photolithography or polishing on the bottom surface of the bonding crystal to reduce the thickness of the bonding crystal.

9. A method for manufacturing an inverted back-pressure sensor, the inverted back-pressure sensor comprising: The main chip includes a body, a Wheatstone bridge, and a first electrical connection structure. A diaphragm is formed on the body, the Wheatstone bridge is disposed on the diaphragm, one end of the first electrical connection structure is connected to the Wheatstone bridge, and the other end extends to the outside of the diaphragm. The cover plate portion includes a cover plate and a second electrical connection structure. The cover plate is bonded to the main body as a whole, and a vacuum cavity is constructed on the side of the diaphragm near the cover plate. The second electrical connection structure penetrates the cover plate, and one end is electrically connected to the first electrical connection structure, while the other end is located on the surface of the cover plate away from the main body, so that the second electrical connection structure can be directly soldered and packaged with an external substrate by SMT. The cover plate has a groove on the side facing the main body, and the main body seals the opening end of the groove to form a closed vacuum cavity; the main body has a pressure-inducing cavity on the side away from the cover plate, and the diaphragm is formed between the pressure-inducing cavity and the vacuum cavity. The production method includes the following steps: B10: Take a wafer and set a Wheatstone bridge on one side of the wafer; B20: A first electrical connection structure connected to a Wheatstone bridge is provided on one side of the wafer after the processing in step B10. B30: Take a silicon wafer or glass sheet and make a through hole through the silicon wafer or glass sheet; B40: Photolithographically etched grooves on one side of the silicon wafer or glass sheet after step B30; B50: The wafer processed in step B20 is bonded to the silicon wafer or glass sheet processed in step B40 and then annealed to form a bonded crystal; wherein the opening of the groove is sealed by the wafer with the first electrical connection structure to form a vacuum cavity. B60: A conductive filler layer is provided inside the through hole; B70: An insulating layer is formed on the surface of the bonded crystal, and a pad is formed that is connected to the conductive filling layer; the pad is located on the side of the conductive filling layer away from the conductive bonding layer, and the pad, the conductive filling layer and the conductive bonding layer constitute a second electrical connection structure. B80: A pressure-receiving cavity is formed on the side of the bonded crystal away from the pad; a diaphragm is formed between the pressure-receiving cavity and the vacuum cavity; B90: Plating solder balls on the bonding pads of the bonded crystal; B100: The bonded crystal with solder balls is cut into pieces to form a flip-chip back-mounted pressure sensor.

10. The method for manufacturing the inverted back-side pressure sensor according to claim 9, wherein, B10: The steps of taking a wafer and setting a Wheatstone bridge on one side of the wafer specifically include: B11: A light boron region is photolithographically patterned on one side of the wafer, and a resistor strip is formed in the light boron region by ion implantation and annealing diffusion process; B12: A boron-rich region is photolithographically formed on a wafer with resistor strips, and conductive lines are formed in the boron-rich region through ion implantation and annealing diffusion processes; the conductive lines are connected to the resistor strips to form a Wheatstone bridge.

11. The method for manufacturing the inverted back-side pressure sensor according to claim 9, wherein, B20: The step of “setting a first electrical connection structure connected to a Wheatstone bridge on one side of the wafer after step B10” specifically includes: The first lead hole is photolithographically etched on the top surface of the wafer forming the Wheatstone bridge; A metal layer is deposited on the top surface of the wafer; The first electrical connection structure is formed in the first lead hole by photolithography to form a metal layer.

12. The method for manufacturing the inverted back-side pressure sensor according to claim 9, wherein, In step B30, before “forming a through-hole through the silicon wafer or glass sheet”, the silicon wafer or glass sheet is thinned to a set thickness.

13. The method for manufacturing the inverted back-side pressure sensor according to claim 9, wherein, Between step B10 and step B20, a second oxide layer is formed on the wafer on which the Wheatstone bridge is formed, covering the Wheatstone bridge and the wafer surface; Between step B30 and step B40, an oxide layer is formed on the inner wall of the through hole and on the outer surface of the silicon wafer or glass sheet.

14. The method for manufacturing the inverted back-side pressure sensor according to claim 13, wherein, After the step of forming a second oxide layer covering the Wheatstone bridge and the wafer surface on the wafer with the Wheatstone bridge and before step B50, the method further includes: forming a silicon nitride layer on the wafer with the second oxide layer over the Wheatstone bridge by deposition and photolithography processes.

15. The method for manufacturing the inverted back-side pressure sensor according to claim 9, wherein, B60: The step of setting a conductive filling layer inside the through-hole specifically includes: B61: An adhesion layer and a seed layer are formed in the through-hole through a deposition process; B62: A conductive filling layer is formed on a wafer with an adhesion layer and a seed layer by an electroplating process.

16. The method for manufacturing the inverted back-side pressure sensor according to claim 9, wherein, Before step "B61: Forming an adhesion layer and a seed layer within the via via using a deposition process", the following is also included: An insulating layer is deposited on the inner wall of the through hole using a deposition process.

17. The method for manufacturing the inverted back-side pressure sensor according to claim 9, wherein, B70: The steps of forming an insulating layer on the surface of the bonded crystal and forming pads that connect to the conductive filling layer specifically include: B71: An insulating layer is formed on the end face where the bonded crystal is connected to the conductive filling layer by an oxidation process; B72: Photolithographically print the fifth lead hole on the insulating layer of the wafer after step B71; B73: A pad is formed at the fifth lead hole using deposition and photolithography processes.

18. The method for manufacturing the inverted back-side pressure sensor according to claim 9, wherein, In step B80, "forming a pressure lead cavity on the side of the bonded crystal away from the pad" further comprises: performing lithography or grinding on the bottom surface of the bonded crystal to thin the thickness of the bonded crystal.

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