CN111722707B

CN111722707B - Manufacturing method of back contact touch sensor and back contact touch sensor

Info

Publication number: CN111722707B
Application number: CN202010337982.9A
Authority: CN
Inventors: 于婷婷; 孙珂; 裴彬彬; 钟鹏; 杨恒; 李昕欣
Original assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Current assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Priority date: 2020-04-26
Filing date: 2020-04-26
Publication date: 2021-10-01
Anticipated expiration: 2040-04-26
Also published as: CN111722707A

Abstract

The invention relates to the technical field of sensors, and discloses a manufacturing method of a back contact touch sensor and the back contact touch sensor, wherein the manufacturing method of the sensor comprises the following steps: bonding a first conductive piece on the front surface of a wafer level unreleased sensing chip with a second conductive piece on the front surface of a wafer level packaging substrate to be bonded; the touch sensor to be released after packaging is released by utilizing the mechanical supporting effect of the packaging substrate, the transfer of the ultrathin sensing chip can be realized, after the releasing process, the back of the ultrathin sensing chip can spontaneously form a continuous silicon film structure, and then the touch sensor is subjected to a temporary bonding process, a substrate back thinning process and a scribing process to obtain a discrete packaged back contact type touch sensor, so that the obtained sensor can be arranged on the flexible substrate through an assembling process. The touch sensor provided by the invention has the characteristics of small size, low packaging cost and large-area scalability.

Description

Manufacturing method of back contact touch sensor and back contact touch sensor

Technical Field

The invention relates to the technical field of sensors, in particular to a back contact touch sensor and a manufacturing method thereof.

Background

The touch sense is a form of sensing the external environment through the skin of human beings, is a general term of mechanical stimulation such as contact, sliding and pressure sense, is caused by the action of pressure and traction force on a touch sensor, has sharp sensing capability and can realize the direct measurement of various characteristics of a target and the environment. People can sense physical characteristics of temperature, shape and the like of an object through touch sense, and also sense motion characteristics of slippage, positive pressure, vibration and the like of the object. Unlike the visual sense, which is irreplaceable although more difficult to mimic than the auditory and visual senses, the tactile sense can express the senses of temperature and force in a quantitative manner.

The touch sensor is used for simulating a touch function in the robot, and has very important practical significance for helping the robot to acquire object and environment information and finish certain operation tasks. The method has very important significance in the field of intelligent robots such as medical equipment, human body artificial limbs, wearable equipment and the like.

However, with the rapid development of the technical fields of intelligent robots, artificial intelligence, virtual reality and the like, the conventional touch sensor is difficult to meet the application requirements, and the touch sensor shows the development trends of global detection, multi-dimensional force detection, miniaturization and the like. The sensor prepared by the existing manufacturing method of the touch sensor has the defect of large size, and the structure of the sensor is only suitable for packaging by the traditional packaging process, so that the sensor has the defects of high packaging cost and difficulty in large-area expansion.

Disclosure of Invention

The invention aims to solve the technical problems of large size, high packaging cost and difficulty in large-area expansion of the touch sensor.

In order to solve the above technical problem, an aspect of the present application discloses a method for manufacturing a back contact tactile sensor, which includes the following steps:

1) etching a Silicon-On-Insulator (SOI) Silicon chip to form a beam-island structure and a support structure, manufacturing a force sensitive resistor, depositing a first barrier layer, manufacturing a metal lead and a first conductive piece which can be used for wafer-level bonding and can realize galvanic cell protection and corrosion resistance, and obtaining a wafer-level unreleased sensing chip;

2) manufacturing a conductive through hole in the packaging substrate, depositing a second barrier layer, preparing a second conductive piece which can be used for wafer-level bonding and can realize primary battery protection and corrosion resistance at the same time, and obtaining a corrosion-resistant wafer-level packaging substrate to be bonded;

3) transferring the wafer-level unreleased sensing chip to the wafer-level packaging substrate to be bonded through a transfer process, bonding the front surface of the wafer-level unreleased sensing chip and the front surface of the wafer-level packaging substrate to be bonded through a first conductive piece and a second conductive piece, and simultaneously realizing the electrical connection of a metal lead wire with the first conductive piece and the second conductive piece to obtain a wafer-level packaged tactile sensor to be released;

4) by utilizing the mechanical supporting effect of the packaging substrate, the bulk silicon layer and the oxygen burying layer on the back of the SOI silicon wafer of the wafer-level packaged touch sensor to be released are removed, the transfer of an ultrathin sensing chip can be realized, and the wafer-level packaged touch sensor is obtained, wherein the back of the ultrathin sensing chip can spontaneously form a continuous silicon film structure after the bulk silicon layer and the oxygen burying layer on the back of the SOI silicon wafer are removed to form a beam-film-island structure, and the back of the ultrathin sensing chip has no electrical structure and does not need subsequent protection;

5) and carrying out a temporary bonding process, a substrate back surface thinning process and a scribing process on the wafer-level packaged touch sensor to obtain a discrete packaged back contact touch sensor unit.

Optionally, the material of the first conductive member and the material of the metal lead are metals and alloys thereof, which are made by sputtering or evaporation process and are resistant to corrosion of alkaline solution such as Cr, Pt or Au;

the second conductive piece is made of gold which is resistant to corrosion of alkaline solution and manufactured through an electroplating process, so that the first conductive piece, the metal lead and the second conductive piece can resist corrosion of the alkaline corrosion solution in a release process after packaging.

Optionally, removing bulk silicon on the back surface of the SOI silicon wafer by an anisotropic wet etching process;

the bonding process of the first conductive piece and the second conductive piece is a gold bonding process, and is used for realizing wafer-level bonding under the conditions of corrosion resistance, conductivity and capability of serving as a primary battery electrode;

the bonding strength of the bonding between the front surface of the packaging substrate and the front surface of the ultrathin sensing chip through the first conductive piece and the second conductive piece is more than or equal to 15MPa, and the packaging substrate and the front surface of the ultrathin sensing chip are used for meeting the mechanical supporting requirement of the chip.

Optionally, the anisotropic wet etching solution includes TMAH, KOH, EPW, etc.;

removing silicon dioxide of an oxygen-buried layer of the SOI silicon wafer by reactive ion etching;

the first barrier layer and the second barrier layer are used as device structure protective layers and need to withstand the anisotropic wet etching process after packaging;

the first barrier layer is a silicon nitride layer manufactured by LPCVD (low pressure chemical vapor deposition) or a silicon carbide layer manufactured by PECVD (plasma enhanced chemical vapor deposition) and the like;

the second barrier layer is a silicon nitride layer formed by LPCVD or a silicon carbide layer formed by PECVD or the like.

Optionally, the surface of the first conductive member and the second conductive member is made of gold, so that gold and an anisotropic corrosive liquid form a galvanic cell, thereby protecting the galvanic cell of the ultrathin sensing chip and preventing the corrosive liquid from corroding a buried oxide layer for a long time to form a pinhole, thereby further underetching and damaging the beam-film-island structure;

the ratio of the sum of the surface areas of the first conductive piece and the second conductive piece to the area of the pinhole is greater than a preset threshold value, so that the primary battery protection can be automatically formed, and the preset threshold value is 8:1 in TMAH solution.

Optionally, the thickness of the package substrate is less than or equal to 300 micrometers;

the thickness of the packaging substrate is greater than or equal to 50 microns, and the minimum thickness of the packaging substrate is determined by the following formula, so that the packaging substrate can provide mechanical support for the ultrathin sensing chip:

wherein h is₁-silicon based package substrate thickness; h is₂-ultra-thin sensor chip thickness; h is₃-the sum of the thicknesses of the first and second conducting members.

The present application discloses in another aspect a back contact tactile sensor comprising an ultra-thin sensing chip and a package substrate;

the ultrathin sensing chip comprises a supporting structure and a sensitive structure, wherein the thickness of the supporting structure is approximately equal to that of the sensitive structure;

the supporting structure is an annular structure, the sensitive structure is arranged in the supporting structure, and the sensitive structure is connected with the inner wall of the supporting structure; the packaging substrate and the ultrathin sensing chip are electrically connected through a conductive piece;

the packaging substrate is used for supporting the ultrathin sensing chip;

the thickness of the ultrathin sensing chip is less than or equal to 20 micrometers, so that the side length of a unit of the ultrathin sensing chip can be less than or equal to 500 micrometers;

the difference between the thickness of the supporting structure and the thickness of the sensitive structure is less than or equal to 3 microns, and the height difference between the front surface of the supporting structure and the front surface of the sensitive structure is less than or equal to 2 microns.

Optionally, the sensitive structure comprises a force sensitive resistor and a beam-film-island structure with mechanical properties determined by the beam structure;

the beam-film-island structure includes the beam structure and a film structure;

the force sensitive resistor is arranged on the front surface of the beam structure and used for measuring piezoresistance;

one end of the beam structure is connected with the inner wall of the supporting structure;

the periphery of the membrane structure is connected with the back of the supporting structure;

the back of the beam structure is connected with the membrane structure, and the thickness of the membrane structure is less than or equal to 1/4 of the thickness of the beam structure;

the thickness relationship between the membrane structure and the beam structure is determined by the following formula:

wherein, the length of the L-beam structure; a-side length of the film structure; b-the width of the beam structure; h is₄-a film structure thickness; h is₅-a beam structure thickness;

the back of the film structure is in direct contact with an object to be measured and is used for protecting the sensitive structure and the metal lead.

Optionally, the connection manner of the force-sensitive resistors on the positive pressure detection unit beam is as shown in fig. 3, and four of the force-sensitive resistors are all variable resistors, wherein two of the force-sensitive resistors are respectively located at the end portions, close to the central mass block, of the front surfaces of one group of symmetric beams, and the other two of the force-sensitive resistors are located at the end portions, close to the support structure, of the front surfaces of the other group of symmetric beams;

the connection mode of the force-sensitive resistors on the shear force detection unit beam is shown in fig. 5, wherein two of the force-sensitive resistors are variable resistors and are located at the end part of the front surface of one group of symmetrical beams close to the central mass block or the end part of the front surface of one group of symmetrical beams close to the support structure, and the other two of the force-sensitive resistors are constant value resistors and are located on the support structure;

the size and the input/output pad of the positive pressure detection unit and the size and the input/output pad of the shearing force detection unit are consistent, so that a standard touch sensing unit is formed, and a touch sensing array can be formed by freely combining different application scenes.

By adopting the technical scheme, the manufacturing method of the back contact touch sensor has the following beneficial effects:

a method of making a back contact tactile sensor, comprising the steps of:

5) the wafer-level packaged touch sensor is subjected to a temporary bonding process, a substrate back thinning process and a scribing process to obtain a discrete packaged back contact type touch sensor unit, so that the obtained touch sensor can be arranged on a flexible substrate through an assembly process, specifically, for example, the back of the packaging substrate is connected to the flexible substrate through a back ball-planting and reflow soldering process, the packaging cost of routing packaging is reduced, and the back sensing area of the back contact type touch sensor is increased.

Due to the mechanical supporting effect of the packaging substrate, the ultra-thin sensing chip can be transferred after the bulk silicon layer and the oxygen buried layer on the back of the SOI silicon wafer of the touch sensor to be released after wafer-level packaging are removed, the ultra-thin sensing chip is manufactured, a small-size back contact type touch sensor unit is obtained, and the development of the technical fields of intelligent robots, artificial intelligence, virtual reality and the like is promoted.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a flow chart of a method of making a back contact tactile sensor according to the present application;

FIG. 2 is a schematic process diagram of a method of making a back contact tactile sensor according to the present application;

FIG. 3 is a schematic diagram of a front side structure of a sensor chip according to an alternative embodiment of the present disclosure;

FIG. 4 is a cross-sectional view of a back contact tactile sensor in an alternative embodiment of the present application;

FIG. 5 is a schematic diagram of a front side structure of a sensor chip according to another alternative embodiment of the present disclosure;

FIG. 6 is a schematic process diagram of a method for manufacturing a back contact tactile sensor according to embodiment 1 of the present application;

fig. 7 is a schematic structural diagram of a back contact tactile sensor according to embodiment 1 of the present application;

fig. 8 is a schematic diagram of a positive pressure detection structure of a sensor chip in embodiment 1 of the present application;

FIG. 9 is a schematic diagram of a shear force detection structure of a sensor chip in embodiment 1 of the present application;

FIG. 10 is a cross-sectional view of a back contact tactile sensor according to embodiment 1 of the present application;

FIG. 11 is a schematic structural diagram of a back contact tactile sensor according to embodiment 2 of the present application;

FIG. 12 is a diagram showing the distribution of force sensors on a first sensor chip according to example 2 of the present application;

FIG. 13 is a diagram showing the distribution of force-sensitive resistors on a second sensor chip according to example 2 of the present application;

FIG. 14 is a cross-sectional view of a back contact tactile sensor in embodiment 3 of the present application;

fig. 15 is a cross-sectional view of a back contact tactile sensor according to embodiment 4 of the present application.

The following is a supplementary description of the drawings:

1-ultrathin sensing chip; 11-a sensitive structure; a 111-beam structure; 112-island structure; 113-a membrane structure; 114-force sensitive resistor; 12-a support structure; 13-an insulating layer; 14-a first barrier layer; 15-a first electrically conductive member; 16-a first lead aperture; 17-a metal lead; 18-a bulk silicon layer; 19-buried oxide layer; 2-a package substrate; 21-a second barrier layer; 22-conductive vias; 23-a thin circular column; 24-an empty annular column; 25-a second wire hole; 26-a second electrically conductive member; 27-stressed polysilicon; 3-wafer level unreleased sensing chip; 4-wafer level packaging substrate to be bonded; 5-the tactile sensor is to be released after wafer level packaging; 6-wafer level packaged rear tactile sensor.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Reference herein to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic may be included in at least one implementation of the present application. In the description of the present application, it is to be understood that the terms "upper", "lower", "top", "bottom", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present application and simplifying the description, and do not indicate or imply that the referred devices or elements must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present application. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Moreover, the terms "first," "second," and the like are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the application described herein are capable of operation in sequences other than those illustrated or described herein.

As shown in fig. 1, 2 and 3, fig. 1 is a flow chart of a method for manufacturing a back contact tactile sensor according to the present application. Fig. 2 is a process diagram of a method for manufacturing a back contact tactile sensor according to the present application. Fig. 3 is a schematic front structure diagram of a sensor chip according to an alternative embodiment of the present disclosure. The application provides a method for manufacturing a back contact touch sensor, which comprises the following steps:

s101, etching a Silicon-On-Insulator (SOI) Silicon chip to form a beam-island structure and a supporting structure 12, manufacturing a force sensitive resistor 114, depositing a first barrier layer 14, manufacturing a metal lead 17 and a first conductive piece 15 which can be used for wafer-level bonding, can realize galvanic cell protection and corrosion resistance, and obtaining a wafer-level unreleased sensing chip 3;

s102, manufacturing a conductive through hole 22 in the packaging substrate 2, depositing a second barrier layer 21, preparing a second conductive piece 26 which can be used for wafer-level bonding and can realize primary battery protection and corrosion resistance, and obtaining a corrosion-resistant wafer-level packaging substrate 4 to be bonded;

s103, transferring the wafer level unreleased sensing chip 3 to the wafer level packaging substrate 4 to be bonded through a transfer process, bonding the front surface of the wafer level unreleased sensing chip 3 and the front surface of the wafer level packaging substrate 4 to be bonded through a first conductive piece 15 and a second conductive piece 26, and simultaneously realizing the electrical connection of a metal lead 17 with the first conductive piece 15 and the second conductive piece 26 to obtain the wafer level packaged tactile sensor 5 to be released;

s104, removing the bulk silicon layer 18 and the oxygen burying layer 19 on the back of the SOI silicon wafer of the wafer-level packaged touch sensor 5 to be released by utilizing the mechanical supporting effect of the packaging substrate 2, so that the ultra-thin sensing chip 1 can be transferred, and the wafer-level packaged touch sensor 6 is obtained, wherein the back of the ultra-thin sensing chip 1 can spontaneously form a continuous silicon film structure 113 after removing the bulk silicon layer 18 and the oxygen burying layer 19 on the back of the SOI silicon wafer to form a beam-film-island structure, and the back of the ultra-thin sensing chip 1 has no electric structure without subsequent protection;

s105, the wafer-level packaged tactile sensor 6 is subjected to a temporary bonding process, a substrate back surface thinning process and a scribing process to obtain a discrete packaged back contact type tactile sensor unit.

The obtained touch sensor can be arranged on the flexible substrate through an assembly process, and specifically, for example, the back surface of the packaging substrate 2 is connected to the flexible substrate through back surface ball-planting and reflow soldering processes, so that the packaging cost of wire bonding packaging is reduced, and the back surface sensing area of the back contact touch sensor is increased; due to the mechanical supporting effect of the packaging substrate 2, the ultra-thin sensing chip 1 can be transferred after the bulk silicon layer 18 and the buried oxide layer 19 on the back of the SOI silicon wafer of the wafer-level packaging to be released from the touch sensor 5 are removed, the ultra-thin sensing chip 1 is manufactured, a small-size back contact type touch sensor unit is obtained, and the development of the technical fields of intelligent robots, artificial intelligence, virtual reality and the like is promoted.

As shown in fig. 2, in an optional implementation, the manufacturing of the force-sensitive resistor 114 in step S101 specifically includes:

a specific region can be defined and formed on the SOI silicon chip through a conventional semiconductor process;

the force-sensitive resistor 114 is formed in a specific region by doping techniques such as ion implantation or diffusion, and the doping materials include, but are not limited to, boron, phosphorus, and the like.

As can be seen from fig. 2, in an alternative embodiment, in step S101, after the manufacturing of the force-sensitive resistor 114, the method further includes:

forming an insulating layer 13 on the SOI wafer by a deposition process including, but not limited to, thermal oxidation, Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), etc., wherein the material of the insulating layer 13 includes, but is not limited to, silicon dioxide;

the beam-island structure is formed by etching the SOI wafer with the insulating layer 13 attached thereto by an etching process, specifically, but not limited to, a deep etching technique, preferably, the etching depth during the etching process is less than the thickness of the top silicon on the front side of the SOI wafer, so that a continuous silicon film can be spontaneously formed on the back side after the release of the tactile sensor 6 after wafer level packaging, thereby forming the beam-film-island structure. In an alternative embodiment, the first barrier layer 14 is formed on the surface of the beam structure 111 of the beam-island structure by a deposition process.

As shown in fig. 2, in an alternative embodiment, the step S101 of manufacturing the first conductive member 15 includes:

etching the first barrier layer 14 to form a first lead hole 16;

a first conductive member 15 is formed on the first lead hole 16 through a deposition process.

In an alternative embodiment, the package substrate 2 in step S102 is a TSV interposer, and the process of manufacturing the TSV interposer is a MEMS conventional process.

Referring to fig. 4, fig. 4 is a cross-sectional view of a back contact tactile sensor in an alternative embodiment of the present application. In an alternative embodiment, the step S102 of depositing the second barrier layer 21 and the preparing the second conductive member 26 specifically includes:

the second barrier layer 21 is formed by a deposition process, and the second barrier layer 21 has an effect of protecting the package substrate 2 from being damaged, and specifically, the second barrier layer 21 is disposed on the upper surface, the lower surface, and the side surface of the package substrate 2.

Etching the second barrier layer 21 to form a second lead hole 25, specifically, defining the region where the second lead hole 25 is located by patterning by using a semiconductor conventional process, then etching the second barrier layer 21 to form the second lead hole 25, sputtering and electroplating a seed layer in the region of the second lead hole 25, and forming a second conductive member 26 with a certain thickness in the region of the second lead hole 25 by using a photolithography patterning process; further, the material of the seed layer includes, but is not limited to, TiW/Au, TiW/Cu, Cr/Au, Cr/Cu, etc.

In an alternative embodiment, the seed layer is etched away by a maskless etching process, leaving the second conductive member 26.

In an alternative embodiment, the first barrier layer 14 and the second barrier layer 21 serve as device structure protection layers and need to withstand a post-packaging anisotropic wet etching process; the first barrier layer 14 is a silicon nitride layer manufactured by LPCVD or a silicon carbide layer manufactured by PECVD or the like; the second barrier layer 21 is a silicon nitride layer formed by LPCVD or a silicon carbide layer formed by PECVD, and has an advantage of reducing the influence of stress on device performance.

In another alternative embodiment, the process of depositing the first barrier layer 14 and the second barrier layer 21 is spin coating or thermal oxidation, and the material of the first barrier layer 14 and the second barrier layer 21 is a polymer material, which can be attached to the surface of the beam structure 111 in a form of a film, such as a polypropylene film, a polyester film, a polyethylene film, and the like.

In an alternative embodiment, the material of the first conductive member 15 and the material of the metal lead 17 are metals resistant to corrosion by alkaline solutions, such as Cr, Pt, or Au, manufactured by a sputtering or evaporation process, and alloys thereof, and the material of the second conductive member 26 is gold resistant to corrosion by alkaline solutions manufactured by a plating process, so that the first conductive member 15, the metal lead 17, and the second conductive member 26 can resist corrosion by alkaline corrosion solutions in a release process after packaging.

In an alternative embodiment, the material of the surfaces of the first conductive member 15 and the second conductive member 26 is gold, so that gold and an anisotropic etching solution form a galvanic cell, thereby achieving galvanic cell protection of the ultra-thin sensing chip 1 and preventing the etching solution from corroding on the buried oxide layer for a long time to form a pinhole, and further underetching the beam-film-island structure; the ratio of the sum of the surface areas of the first conductive member 15 and the second conductive member 26 to the area of the pinhole is greater than a preset threshold value, so that galvanic cell protection can be automatically formed, the structural integrity of the device is protected, and the yield of the transfer process is improved, wherein the preset threshold value is 8:1 in a TMAH solution.

In an alternative embodiment, the bonding process of the first conductive member 15 and the second conductive member 26 is a gold bonding process, which is used to achieve wafer level bonding under the conditions of corrosion resistance, conductivity and capability of being used as a galvanic cell electrode; the bonding strength of the front surface of the package substrate 2 and the front surface of the ultra-thin sensing chip 1 bonded through the first conductive member 15 and the second conductive member 26 is greater than or equal to 15MPa, which is used for meeting the mechanical supporting requirement of the chip, in another optional implementation manner, the bonding process of the first conductive member 15 and the second conductive member 26 may also be a gold-tin bonding, copper-tin bonding, or gold hot-press bonding, and the like, and it needs to be noted that the selection of the bonding process in the step is to ensure that the release process of the tactile sensor 6 after the subsequent wafer level package does not affect the bonding strength and quality.

In an optional implementation mode, removing bulk silicon on the back surface of the SOI silicon wafer by an anisotropic wet etching process; the anisotropic wet etching solution comprises TMAH, KOH, EPW and the like, and preferably TMAH etching solution is adopted; removing the silicon dioxide on the buried oxide layer 19 of the SOI silicon chip by reactive ion etching, wherein the step of removing the buried silicon dioxide by reactive ion etching is a conventional integrated circuit process;

in another alternative embodiment, the to-be-released tactile sensor 5 after wafer level packaging is released by a DRIE reactive ion dry etching process by using the mechanical support effect of the packaging substrate, and in order to ensure that the mechanical strength of the packaging substrate 2 can withstand the pressure difference caused by the substrate cooling process of the reactive ion etcher, the initial thickness of the wafer level packaging substrate 2 is greater than or equal to 300 micrometers.

In another alternative embodiment, the mechanical support of the package substrate is used, via XeF₂The tactile sensor 5 to be released after wafer-level packaging is released by isotropic dry etching, the first barrier layer 14 and the second barrier layer 21 are made of silicon dioxide or silicon carbide, the first barrier layer 14 and the second barrier layer 21 are used as device structure protective layers and need to resist the isotropic dry etching of XeF2 and the like, and preferably, the first conductive piece 15, the second conductive piece 26 and the metal lead 17 are made of materials of aluminum or chromium and the like which resist XeF₂Corroding the metal.

In an optional embodiment, in step S104, the method further includes thinning the tactile sensor 5 to be released after the wafer level package to a certain extent by using a mechanical grinding process, the thinned thickness being limited by the size of the cavity, and then performing anisotropic wet etching or DRIE or other reactive ion dry etching or XeF₂And (5) carrying out processes such as isotropic dry etching and the like, and carrying out back release by utilizing the mechanical supporting effect of the packaging substrate. In an alternative embodiment, the package substrate 2 has a thickness of 300 μm or less;

the thickness of the package substrate 2 is greater than or equal to 50 micrometers, and the minimum thickness of the package substrate 2 is determined by the following formula, so that the package substrate 2 can provide mechanical support for the ultra-thin sensor chip 1:

wherein h is₁Silicon-based package substrate 2 thickness; h is₂-the thickness of the ultra-thin sensor chip 1; h is₃-the sum of the thicknesses of the first and second conducting members. For example, when the side length of the sensor chip is less than or equal to 500 micrometers, the thickness of the package substrate 2 is required to be greater than or equal to 50 micrometers.

Specifically, the above equation 1 is derived from the condition that when the package substrate 2 is subjected to a uniform load and undergoes a small-deflection pure bending, the shear stress T can be considered due to the axisymmetric uniform deformation of the package substrate 2_rθ， T_θz0, the positive stress in the z direction is considered to be 0 due to the single-sided stress of the package substrate 2, and only T is in the package substrate 2_r，T_θAnd T_rzAnd (3) simultaneously obtaining a differential equation under a polar coordinate according to a force balance equation and a moment balance equation by the three non-zero stress components, namely the following formula:

wherein, P is a concentrated load; d1-bending stiffness.

And then according to the boundary conditions that the boundary conditions of the center fixed end and the free end of the packaging substrate 2 are that the radial stress is 0 and the applied moment is 0 and a formula 2, calculating to obtain the tensile quantity of the ultrathin sensing chip 1 caused by the deflection of the packaging substrate as follows:

wherein, a₁-package substrate side length.

The transverse tensile stress of the ultrathin sensing chip 1 is obtained according to the formula 3 as follows:

wherein E is Young's modulus.

Similarly, the maximum stress of the surface of the ultrathin sensing chip 1 is calculated as follows:

wherein, a₂-the side length of the sensor chip.

According to the maximum stress T of the ultrathin sensing chip 1_mTransverse tensile stress T of ultrathin sensing chip 1 caused by bending of packaging substrate 2_xxThe ratio is 10% smaller, that is, equation 1 can be obtained according to equation 4 and equation 5

I.e., the minimum thickness of the back contact sensor package substrate 2 satisfies equation 1.

As shown in fig. 4, the present application discloses in another aspect a back-contact tactile sensor comprising an ultra-thin sensing chip 1 and a package substrate 2; the ultrathin sensing chip 1 comprises a supporting structure 12 and a sensitive structure 11, wherein the thickness of the supporting structure 12 is approximately equal to that of the sensitive structure 11, namely the difference between the thickness of the supporting structure 12 and the thickness of the sensitive structure 11 is less than or equal to 3 micrometers, and the height difference between the front surface of the supporting structure 12 and the front surface of the sensitive structure 11 is less than or equal to 2 micrometers; the supporting structure 12 is an annular structure, the sensitive structure 11 is arranged in the supporting structure 12, and the sensitive structure 11 is connected with the inner wall of the supporting structure 12; the packaging substrate 2 and the ultrathin sensing chip 1 are electrically connected through a conductive piece; the packaging substrate 2 is used for supporting the ultrathin sensing chip 1;

the thickness of the ultrathin sensing chip 1 is less than or equal to 20 micrometers, so that the unit side length of the ultrathin sensing chip 1 can be less than or equal to 500 micrometers.

In an alternative embodiment, the conductive members include a first conductive member 15 and a second conductive member 26, the first conductive member 15 is disposed on the front surface of the supporting structure 12, the second conductive member 26 is disposed on the front surface of the package substrate 2 corresponding to the first conductive member 15, the package substrate 2 and the ultra-thin sensor chip 1 are connected by bonding the first conductive member 15 and the second conductive member 26, and a gap exists between the first conductive members 15 and a gap exists between the second conductive members 26, so that a bonding cavity of the package substrate 2 and the ultra-thin sensor chip 1 is communicated with the atmosphere.

In an alternative embodiment, the sensitive structure 11 includes a force sensitive resistor 114 and a beam-film-island structure with mechanical properties determined by the beam structure 111; the beam-film-island structure includes the beam structure 111 and the film structure 113; the force sensitive resistor 114 is arranged on the front surface of the beam structure 111 and used for measuring piezoresistance; one end of the beam structure 111 is connected to the inner wall of the support structure 12; the periphery of the membrane structure 113 is connected to the back of the support structure 12; the back of the beam structure 111 is connected with the film structure 113, and the thickness of the film structure 113 is less than or equal to 1/4 of the thickness of the beam structure 111; the thickness relationship between the membrane structure 113 and the beam structure 111 is determined by the following equation:

wherein the L-beam structure 111 is long; a-the side length of the film structure 113; b-beam structure 111 width; h is₄-a film structure 113 thickness; h is₅-beam structure 111 thickness;

as can be seen from formula 6, the stiffness coefficient of the beam structure 111 is greater than the stiffness coefficient of the film structure 113, the beam structure 111 mainly plays a role of mechanical support, and the back surface of the film structure 113 is in direct contact with an object to be tested, and is used for protecting the sensitive structure 11 and the metal lead 17.

In an alternative embodiment, the beam-film-island structure further comprises an island structure 112, one end of the beam structure 111 being connected to the support structure 12, and the other end of the beam structure 111 being connected to the island structure 112.

In an alternative embodiment, the force-sensitive resistors 114 on the positive pressure detecting unit beams are connected as shown in fig. 3, and four of the force-sensitive resistors 114 are all variable resistors, wherein two of the force-sensitive resistors 114 are respectively located at the end portions of the front surfaces of one set of symmetric beams close to the central mass, and the other two force-sensitive resistors 114 are located at the end portions of the front surfaces of the other set of symmetric beams close to the supporting structure 12;

the connection mode of the force-sensitive resistor 114 on the beam of the shear force detection unit is shown in fig. 5, and fig. 5 is a schematic front structural view of a sensor chip in another alternative embodiment of the present application. Two of the force-sensitive resistors 114 are variable resistors and are located at the end of the front surface of one set of symmetric beams close to the central mass block or at the end of the front surface of one set of symmetric beams close to the support structure 12, and the other two are constant value resistors and are located on the support structure 12.

In order to better embody the advantageous effects of the back contact tactile sensor disclosed in the present application, a detailed description will be given below.

Example 1

The embodiment mainly provides a method for manufacturing a back contact touch sensor, and the scheme of the embodiment mainly includes that an SOI silicon wafer is used for manufacturing an MEMS micromechanical sensing structure, as shown in fig. 6 and 7, fig. 6 is a schematic process diagram of the method for manufacturing the back contact touch sensor in embodiment 1 of the present application; fig. 7 is a schematic structural diagram of a back contact tactile sensor according to embodiment 1 of the present application. Referring to fig. 4, the beam-film-island structure of the back contact tactile sensor includes 4 beam structures 111, and the specific process implementation steps are as follows:

1) providing an SOI silicon wafer, and growing a silicon dioxide layer on the SOI silicon wafer by thermal oxidation, wherein the thickness of the silicon dioxide layer is

Etching the layer to form a specific region, implanting and diffusing boron ions to form the force-sensitive resistor 114, specifically, the boron ion doping concentration of the specific region is 1 × 10¹⁷-1×10²⁰atoms/cm²。

2) An insulating layer 13 is formed on the surface of the SOI silicon chip, the material of the insulating layer 13 is photoresist, silicon dioxide outside a force sensitive resistor 114 area is etched, the influence of silicon dioxide film stress on a device can be reduced to a certain extent, then silicon on the top layer of the SOI silicon chip is etched to form a beam-film-island structure, and specifically, the etching depth range is 9-13 mu m.

3) Depositing a layer of low-stress silicon nitride as a first barrier layer 14 on the sensitive structure 11 by LPCVD, the thickness of the first barrier layer 14 being in the range of

4) Using photoresist as mask, etching the first barrier layer 14 and the silicon dioxide layer to form a first lead hole 16, and then forming a metal lead 17 by metal sputtering and patterning, as can be seen from fig. 3, specifically, the composition of the metal lead 17 is Cr/Pt/Au, and the thickness of the metal lead 17 is in the range of Cr/Pt/Au

As shown in fig. 6, a gap exists between the first conductive members 15 and a gap exists between the second conductive members 26, so that a gap exists at a connection position between the ultra-thin sensing chip 1 and the package substrate 2, and thus the pressure of the inner cavity and the outer cavity of the back contact touch sensor are the same, and the wafer-level unreleased sensing chip 3 is obtained.

The metal lead 17 is connected to a force sensitive resistor 114 to form a Wheatstone bridge.

As shown in fig. 8 and 9, fig. 8 is a schematic diagram of a positive pressure detection structure of a sensor chip in embodiment 1 of the present application; FIG. 9 is a schematic diagram of a shear force detection structure of a sensor chip in embodiment 1 of the present application; as shown in fig. 8, 8 force-sensitive resistors 114 are distributed on the sensitive structure 11, that is, the beam-film-island structure, and as can be seen from fig. 8, the circuit is a circuit formed by connecting two sets of series circuits in parallel, when the back surface of the back-contact tactile sensor is subjected to a positive pressure F1, the change in stress at one end of the beam structure 111 close to the island structure 112 changes the magnitude of the resistance of the force-sensitive resistor 114, and the acting force with the target object can be measured by measuring the output voltage of the tactile sensor, as can be seen from fig. 8, under the action of FI, the beam structure 111 close to the island structure 112 is in a compressive stress region, that is, the resistances of R5, R6, R7, and R8 are reduced; and the other end of the beam structure 111 is in a tensile stress region, i.e., R1, R2, R3, R4 increase in resistance.

Of course, the metal lead 17 shown in fig. 9 may be connected to the circuit according to actual requirements. When the back surface of the back contact tactile sensor is subjected to a tangential force F2, in the shearing direction, R9 and R11 are in a compressive stress region, and R10 and R12 are in a tensile stress region.

5) As shown in fig. 10, fig. 10 is a cross-sectional view of a back contact tactile sensor in embodiment 1 of the present application; referring to fig. 2, a package substrate 2 is prepared, where the package substrate 2 is a TSV interposer, and the TSV interposer is a heavily doped low-resistance silicon wafer.

6) A thin circular column 23 is etched on top of the package substrate 2 using a plasma deep etching technique (ICP-DRIE), preferably, the thin circular column 23 has a diameter ranging from 2 to 6 μm and a height ranging from 80 to 140 μm.

7) A silicon dioxide layer is grown on the inner side wall of the thin circular column 23 by a thermal oxidation process, and the thickness of the silicon dioxide layer is within the range

The etched thin annular column 23 is filled with low-stress polysilicon 27 by an LPCVD process, in order to ensure the filling quality, the low-stress polysilicon 27 on the surface of the silicon wafer can be deposited twice within the range of 1-3 μm each time, and preferably, the low-stress polysilicon 27 is etched off.

8) Depositing a layer of silicon nitride on the upper surface, the lower surface and the side surface of the packaging substrate 2 by a deposition process to form a second barrier layer 21, wherein the thickness range of the second barrier layer 21 is

9) By patterned etching of the second barrier layer 21And a silicon dioxide layer forming a second lead hole 25, sputtering a Cr/Pt/Au seed layer in the second lead hole 25, wherein the thickness range of the Cr/Pt/Au seed layer is

And forming a second conductive member 26 by an electroplating process, specifically, the height of the second conductive member 26 is 3-8 μm, and removing the seed layer by maskless etching to obtain the wafer-level packaging substrate 4 to be bonded.

11) And carrying out gold-gold hot-pressure welding on the wafer-level unreleased sensing chip 3 and the wafer-level packaging substrate to be bonded 4, transferring the wafer-level unreleased sensing chip 3 to the wafer-level packaging substrate to be bonded 4, and specifically, carrying out vacuum at the temperature of 300-500 ℃ to obtain the wafer-level packaged touch sensor to be released 5.

12) The back contact touch sensor 8 to be released is placed and the bulk silicon layer 18 of the SOI silicon chip is removed through a KOH solution corrosion process, and the buried oxide layer 19 of the SOI silicon chip is removed through a gas-phase HF corrosion process. Specifically, during the KOH etching process, the ratio of the sum of the areas of the first conductive member 15 and the second conductive member 26 to the pore area of the buried oxide layer 19 of the SOI silicon wafer is greater than 8.

13) The top of the packaging substrate 2 is subjected to dry etching by a plasma deep etching technology to form an empty circular column 24, the diameter range of the empty circular column 24 is 30-50 mu m, the thickness range is 240-300 mu m, the empty circular column is subjected to dry etching until the empty circular column is connected with the fine circular column 23 etched on the front side to form an insulating ring, and the middle of the empty circular column 24 is provided with a low-resistance silicon conductive column.

14) Due to the low TSV density, copper wiring and ball mounting can be performed on the bottom of the package substrate 2. And manufacturing a force guide column on the contact surface of the force of the back contact touch sensor to obtain the wafer-level packaged touch sensor 6.

The wafer-level packaged touch sensor 6 is subjected to a temporary bonding process, a substrate back surface thinning process and a scribing process to obtain a discrete packaged back contact touch sensor unit;

the bottom of the discrete back contact type touch sensor unit distributed with the copper wires is connected with a flexible PCB by an SMT machine, and the packaging process is replaced by the assembling processes such as the surface mounting process, the reflow soldering process and the like, so that the low-cost large-area flexible touch sensing array is formed.

Example 2

As shown in fig. 11, fig. 11 is a schematic structural diagram of a back contact tactile sensor in embodiment 2 of the present application; this embodiment mainly provides another method for manufacturing a back contact tactile sensor, and for simplifying this application, the same parts as those in embodiment 1 will not be described again.

The main differences between the present application and the method for manufacturing the back contact tactile sensor in embodiment 1 are as follows:

the packaging substrate 2 is a conventional TSV adapter plate manufactured by using a double-polished low-resistance silicon wafer, the sensitive structure 11 comprises two beam structures 111, the two beam structures 111 are located on the same straight line and located on two sides of the island structure 112 respectively, and the transferred wafer level sensor is released by adopting a dry etching process. The specific distinguishing process steps comprise the following steps:

1) the formed beam-film-island structure is a two-beam structure;

2) a metal lead 17 is formed at the first lead hole 16, and the metal lead 17 is connected with the force sensitive resistor 114 to form a Wheatstone bridge.

As shown in fig. 12 and fig. 13, fig. 12 is a schematic diagram of the distribution of force-sensitive resistors on the first sensor chip in embodiment 2 of the present application; FIG. 13 is a diagram showing the distribution of force-sensitive resistors on a second sensor chip according to example 2 of the present application; as shown in fig. 12 and fig. 13, four force-sensitive resistors 114 are distributed on the beam-film-island structure of the sensor chip, and two ends of each beam structure 111 are respectively provided with one force-sensitive resistor 114.

3) The manufacturing process of the package substrate 2 and the process of transferring and bonding the ultrathin sensor chip 1 to the package substrate 2 are the same as those of embodiment 1, because the subsequent release is performed by adopting a dry process, the initial thickness of the provided package substrate 2 is more than or equal to 300 micrometers.

4) And (3) performing dry etching on the wafer level touch sensor after transfer bonding by using a plasma deep etching technology (ICP-DRIE), removing bulk silicon on the back of the SOI silicon wafer, and removing an oxygen buried layer on the back of the SOI silicon wafer by using a BOE solution (Buffered Oxide etch) to obtain the wafer level packaged touch sensor 6.

The back contact tactile sensor provided by the method has the advantages of high strength and low packaging process cost.

Example 3

Fig. 14 is a cross-sectional view of a back contact tactile sensor according to embodiment 3 of the present application, as shown in fig. 14; and refer to fig. 2. In order to simplify the present application, the same portions of this embodiment as those of embodiment 1 will not be described again.

The difference between the method for manufacturing the back contact touch sensor in embodiment 1 and the package substrate 2 is that a conventional silicon wafer is used to manufacture a TSV interposer with a conductive through hole 22, and an ultrathin sensor chip is transferred onto the package substrate 2. The specific distinguishing process steps comprise the following steps:

1) etching a Silicon-On-Insulator (SOI) Silicon wafer to form a beam-island structure and a support structure 12, manufacturing a force sensitive resistor 114, depositing a first barrier layer 14, manufacturing a metal lead 17 and a first conductive piece 15, and obtaining a wafer-level unreleased sensing chip 3, wherein the specific process and parameters are the same as those of embodiment 1;

2) providing a double polished silicon wafer to manufacture a packaging substrate 2, and growing an oxide layer on the silicon wafer for the first time, wherein the thickness range is 1-4 microns;

3) photoetching the front side of the silicon wafer, removing silicon dioxide at the window, and etching the conductive through hole 22 on the front side of the silicon wafer by a dry method by utilizing the plasma deep etching technology (ICP-DRIE);

4) removing residual silicon dioxide layers on the front side and the back side of the silicon wafer by using a BOE solution (Buffered Oxide Etchant), and performing thermal oxidation again to form the silicon dioxide layers serving as the insulating layers of the TSV, wherein the thickness range of the silicon dioxide layers is 1-4 microns, so as to obtain the TSV silicon wafer;

5) carrying out gold-gold bonding on the TSV silicon chip and the gold layer supported by the bare silicon chip to form an electroplating seed layer, carrying out copper electroplating filling on the TSV silicon chip, removing the bare supporting silicon chip, and obtaining a wafer-level packaging substrate 4 to be bonded;

6) carrying out gold-gold hot pressure welding on the wafer level unreleased sensing chip 3 and a wafer level packaging substrate 4 to be bonded, transferring the wafer level unreleased sensing chip 3 to the wafer level packaging substrate 4 to be bonded, releasing the wafer level unreleased sensing chip after bonding is finished, and carrying out wafer level packaging and then carrying out a touch sensor 6;

7) the wafer-level packaged back touch sensor unit 6 is subjected to a temporary bonding process, a substrate back thinning process and a scribing process to obtain a discrete packaged back touch sensor unit.

Example 4

In order to simplify the present application, the same portions as those in embodiment 3 will not be described again. Fig. 15 is a cross-sectional view of a back contact tactile sensor according to embodiment 4 of the present application, as shown in fig. 15. Referring to fig. 14, the main difference between the manufacturing method of the back contact tactile sensor provided in this embodiment and that in embodiment 3 is that the position of the conductive via 22 is made to correspond to the position of the center of the sensor, so as to meet the requirements of different application scenarios.

The above description is only exemplary of the present application and should not be taken as limiting, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a back contact tactile sensor, comprising the steps of:

1) manufacturing a force sensitive resistor (114) On an SOI (Silicon-On-Insulator) Silicon chip, and etching to form a beam-island structure (112) and a support structure (12), wherein the force sensitive resistor is positioned On the beam structure of the beam-island structure (112); depositing a first barrier layer (14) on the surface of the SOI silicon wafer, and etching the first barrier layer (14) to form a first lead hole (16); forming a first conductive member (15) on the first lead hole (16) by a deposition process, the first conductive member (15) being located on the support structure (12); forming metal leads (17) on the beam-island structure (112) and the support structure (12) by metal sputtering and patterning to obtain a wafer-level unreleased sensing chip (3); the metal lead (17) and the first conductive member (15) can be used for wafer level bonding and primary battery protection at the same time; and the metal lead (17) and the first electrically conductive member (15) are corrosion resistant; the metal lead (17) is electrically connected with the force-sensitive resistor (114);

2) manufacturing a conductive through hole (22) in a package substrate (2), depositing a second barrier layer (21) on the surface of the package substrate (2), and etching the second barrier layer (21) to form a second lead hole (25); forming a second conductive piece (26) which can be used for wafer-level bonding, primary battery protection and corrosion resistance on the second lead hole (25) through a deposition process to obtain a corrosion-resistant wafer-level packaging substrate (4) to be bonded; the second conductive member (26) corresponds to the first conductive member (15);

3) transferring the wafer-level unreleased sensing chip (3) onto the wafer-level packaging substrate (4) to be bonded through a transfer process, bonding the front surface of the wafer-level unreleased sensing chip (3) and the front surface of the wafer-level packaging substrate (4) to be bonded through a first conductive piece (15) and a second conductive piece (26), and simultaneously realizing the electrical connection of a metal lead (17) with the first conductive piece (15) and the second conductive piece (26) to obtain a wafer-level packaged tactile sensor (5) to be released;

4) by utilizing the mechanical supporting effect of the packaging substrate (2), a bulk silicon layer (18) and an oxygen burying layer (19) on the back surface of the SOI silicon wafer of the wafer-level packaged tactile sensor (5) to be released are removed, so that the ultra-thin sensing chip (1) can be transferred, and the wafer-level packaged tactile sensor (6) is obtained, wherein the back surface of the ultra-thin sensing chip (1) can spontaneously form a continuous silicon film structure (113) after the bulk silicon layer (18) and the oxygen burying layer (19) on the back surface of the SOI silicon wafer are removed to form a beam-film-island structure (112), and the back surface of the ultra-thin sensing chip (1) is free of an optical structure without subsequent protection;

5) and carrying out a temporary bonding process, a substrate back thinning process and a scribing process on the wafer-level packaged touch sensor (6) to obtain a discrete packaged back touch sensor unit.

2. The method of manufacturing a back contact tactile sensor according to claim 1,

the material of the first conductive piece (15) and the material of the metal lead (17) are metals and alloys thereof which are made by sputtering or evaporation technology and are resistant to corrosion of alkaline solutions such as Cr, Pt or Au;

the second conductive member (26) is made of gold which is resistant to corrosion of alkaline solutions and is manufactured through an electroplating process, so that the first conductive member (15), the metal lead (17) and the second conductive member (26) can resist corrosion of alkaline corrosion solutions in a release process after packaging.

3. The method of manufacturing a back contact tactile sensor according to claim 1,

removing bulk silicon on the back surface of the SOI silicon wafer by an anisotropic wet etching process;

the bonding process of the first conductive piece (15) and the second conductive piece (26) is a gold bonding process, and is used for realizing wafer-level bonding under the conditions of corrosion resistance, conductivity and capability of serving as a primary battery electrode;

the bonding strength of the front surface of the packaging substrate (2) and the front surface of the ultrathin sensing chip (1) bonded through the first conductive piece (15) and the second conductive piece (26) is greater than or equal to 15MPa, and the packaging substrate is used for meeting the mechanical supporting requirement of the chip.

4. The method of manufacturing a back contact tactile sensor according to claim 3,

the anisotropic wet etching solution comprises TMAH, KOH, EPW and the like;

removing silicon dioxide of an oxygen burying layer (19) of the SOI silicon wafer by reactive ion etching;

the first barrier layer (14) and the second barrier layer (21) are used as device structure protective layers and need to withstand a post-packaging anisotropic wet etching process;

the first barrier layer (14) is a silicon nitride layer manufactured by LPCVD (low pressure chemical vapor deposition) or a silicon carbide layer manufactured by PECVD (plasma enhanced chemical vapor deposition) and the like;

the second barrier layer (21) is a silicon nitride layer manufactured by LPCVD (low pressure chemical vapor deposition) or a silicon carbide layer manufactured by PECVD (plasma enhanced chemical vapor deposition) and the like.

5. The method of manufacturing a back contact tactile sensor according to claim 4,

the surfaces of the first conductive piece (15) and the second conductive piece (26) are made of gold, so that gold and anisotropic corrosive liquid form a galvanic cell, the galvanic cell protection of the ultrathin sensing chip (1) is realized, and the corrosive liquid is prevented from corroding a buried oxide layer for a long time to form a pinhole, so that the beam-film-island structure (112) is further underetched and damaged;

the ratio of the sum of the surface areas of the first conductive piece (15) and the second conductive piece (26) to the area of the pinhole is greater than a preset threshold value, so that galvanic cell protection can be automatically formed, and the preset threshold value is 8:1 in a TMAH solution.

6. The method of manufacturing a back contact tactile sensor according to claim 1,

the thickness of the packaging substrate (2) is less than or equal to 300 microns;

the thickness of the packaging substrate (2) is greater than or equal to 50 microns, and the minimum thickness of the packaging substrate (2) is determined by the following formula, so that the packaging substrate (2) can provide mechanical support for the ultrathin sensing chip (1):

7. A back contact tactile sensor produced by the production method according to any one of claims 1 to 6, comprising an ultra-thin sensor chip (1) and a package substrate (2);

the ultrathin sensing chip (1) comprises a supporting structure (12) and a sensitive structure (11), wherein the thickness of the supporting structure (12) is approximately equal to that of the sensitive structure (11);

the supporting structure (12) is an annular structure, the sensitive structure (11) is arranged in the supporting structure (12), and the sensitive structure (11) is connected with the inner wall of the supporting structure (12);

the sensitive structure (11) comprises a force sensitive resistor (114) and a beam-film-island structure with mechanical characteristics determined by a beam structure (111); the beam-film-island structure (112) comprises the beam structure (111), an island structure (112) and a film structure (113); the force-sensitive resistor (114) is arranged on the front surface of the beam structure (111) and used for measuring piezoresistance; one end of the beam structure (111) is connected with the inner wall of the support structure (12); the other end of the beam structure (111) is connected with an island structure (112); the periphery of the membrane structure (113) is connected to the back of the support structure (12); the back of the beam structure (111) is connected with the membrane structure (113);

a conductive through hole (22) is formed in the packaging substrate (2);

the packaging substrate (2) and the ultrathin sensing chip (1) are electrically connected through a conductive piece;

the conductive parts comprise a first conductive part (15) and a second conductive part (26), the first conductive part (15) is arranged on the front surface of the supporting structure (12), the second conductive part (26) is arranged on the front surface of the packaging substrate (2) corresponding to the first conductive part (15), and the packaging substrate (2) and the ultrathin sensing chip (1) are in bonding connection with the second conductive part (15) through the first conductive part (15);

metal leads (17) are arranged on the beam structure (111), the island structure (112) and the support structure (12), and the metal leads (17) are electrically connected with the first conductive piece (15) and the force-sensitive resistor (114);

the packaging substrate (2) is used for supporting the ultrathin sensing chip (1);

the thickness of the ultrathin sensing chip (1) is less than or equal to 20 micrometers, so that the unit side length of the ultrathin sensing chip (1) can be less than or equal to 500 micrometers;

the difference between the thickness of the supporting structure (12) and the thickness of the sensitive structure (11) is less than or equal to 3 microns, and the height difference between the front surface of the supporting structure (12) and the front surface of the sensitive structure (11) is less than or equal to 2 microns.

8. The tactile sensor according to claim 7, wherein the membrane structure (113) has a thickness less than or equal to 1/4 of the beam structure (111);

the thickness relationship between the membrane structure (113) and the beam structure (111) is determined by the following formula:

the back surface of the film structure (113) is in direct contact with an object to be tested and is used for protecting the sensitive structure (11) and the metal lead (17).

9. The back contact tactile sensor of claim 8,

four force-sensitive resistors (114) are arranged on the positive pressure detection unit beam, the four force-sensitive resistors (114) are all variable resistors, two force-sensitive resistors (114) are respectively positioned at the end part of the front surface of one group of symmetrical beams close to the central mass block, and the other two force-sensitive resistors (114) are positioned at the end part of the front surface of the other group of symmetrical beams close to the supporting structure (12);

the shear force detection unit beam is provided with four force-sensitive resistors (114), wherein two force-sensitive resistors (114) are variable resistors and are positioned at the end part of the front surface of one group of symmetrical beams close to the central mass block or the end part of the front surface of one group of symmetrical beams close to the support structure (12), and the other two force-sensitive resistors are constant value resistors and are positioned on the support structure (12);