High-reliability pressure sensor preparation method and pressure sensor
Through ICP etching process and back pressure feeding technology, the problem of difficult control of strain film size and thickness in pressure sensors is solved, and the preparation of small-range pressure sensors and the long-term maintenance of vacuum is achieved, which improves the stability and reliability of the sensor.
Patent Information
- Application Number
- CN202510096471.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-21
- Publication Date
- 2025-05-02
AI Technical Summary
During the production process, the size and thickness of the strain film of the existing pressure sensors are difficult to accurately control, and cannot meet the requirements of small-range pressure sensors. At the same time, there are problems such as the vacuum degree cannot be maintained for a long time and the nonlinear error is large.
ICP etching Cavity process on the back of the substrate is used to accurately control the size and thickness of the pressure-sensitive film, and maintain the vacuum degree through the back pressure injection to optimize the nonlinear error of the sensor.
The preparation of a small-range pressure sensor is realized, ensuring long-term maintenance of vacuum, improving the stability and reliability of the sensor, and optimizing nonlinear errors.
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Figure CN119911869A_ABST
Abstract
Description
Technical Field
[0001] The embodiments of the present disclosure belong to the technical field of pressure sensors, and particularly relate to a method for preparing a high-reliability pressure sensor and a pressure sensor. Background Art
[0002] Pressure sensors are micro-electromechanical systems (MEMS) devices used to measure pressure. These sensors are widely used in many fields such as automobiles, industrial control, weather monitoring, medical equipment, and consumer electronics. They can convert physical pressure changes into electrical signal outputs, thereby achieving accurate monitoring of the pressure in the environment or system.
[0003] At present, in the traditional manufacturing process of pressure sensors, the size and thickness of the strain film cannot be accurately controlled, and cannot meet all the requirements for the preparation of small-range pressure sensors. In addition, the pressure sensors in the related art also have the problem that the vacuum degree cannot be maintained for a long time, and the problem of large nonlinear error.
[0004] Therefore, how to solve the above problems has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention
[0005] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a method for preparing a high-reliability pressure sensor and a pressure sensor.
[0006] According to a first aspect of an embodiment of the present disclosure, there is provided a method for preparing a high-reliability pressure sensor, comprising: providing a substrate;
[0007] forming an oxide layer on the front side of the substrate;
[0008] Using an etching process to pattern the oxide layer to form a cavity exposing the front side of the substrate and a mass block;
[0009] forming a device layer covering the mass block and the cavity on a surface of the mass block;
[0010] Performing ion implantation on the front surface of the device layer to form a varistor corresponding to the mass block;
[0011] forming a polysilicon layer covering the device layer and the varistor on the front side of the device layer, wherein the polysilicon layer has a varistor-sensitive region corresponding to the varistor;
[0012] Etching the polysilicon layer to form a contact hole exposing the surface of the device layer on the periphery of the pressure-sensitive region;
[0013] forming a metal lead in the contact hole;
[0014] Performing back etching on the back side of the substrate by using an inductively coupled plasma etching process, and stopping at the mass block and the device layer, so as to form a back cavity connected to the cavity and used for pressure injection;
[0015] The glass sheet with the groove is bonded to the pressure-sensitive area by a bonding process to complete the preparation.
[0016] Furthermore, after the glass sheet is bonded to the pressure-sensitive region, the groove and the polysilicon layer form a vacuum cavity in the pressure-sensitive region;
[0017] Before the glass sheet with the groove is bonded to the pressure-sensitive area by the bonding process, the method further includes: arranging a vacuum getter in the groove.
[0018] Optionally, the material of the oxide layer includes silicon oxide, wherein the silicon oxide layer is grown on the front side of the substrate by using a thermal oxidation process.
[0019] Optionally, after forming a device layer covering the mass block and the cavity on the surface of the mass block, the method further includes: performing a chemical mechanical polishing thinning process on the device layer.
[0020] Optionally, a chemical vapor deposition process is used to form a polysilicon layer covering the device layer and the varistor on the front side of the device layer.
[0021] Optionally, an ion beam etching process is used to form a contact hole exposing the surface of the device layer on the periphery of the pressure-sensitive area.
[0022] Optionally, a magnetron sputtering process is used to form a metal lead in the contact hole.
[0023] Optionally, an ion beam etching process is used to pattern and etch the oxide layer to form a cavity exposing the front side of the substrate and a mass block.
[0024] Optionally, the glass sheet with the groove is bonded to the pressure-sensitive area by an anodic bonding process.
[0025] According to a second aspect of an embodiment of the present disclosure, a high-reliability pressure sensor is provided. The sensor is prepared according to the method described above.
[0026] The beneficial effects of the embodiments of the present disclosure include:
[0027] In the present invention, the ICP Cavity etching process on the back side of the substrate is adopted. Compared with the traditional Cavity-SOI process, the size and thickness of the pressure-sensitive film (also called strain film) can be accurately controlled, the preparation of a large back cavity and low thickness pressure-sensitive film can be achieved, and the preparation of a small-range pressure sensor can be achieved.
[0028] The back side of the substrate is pressurized. For small-range pressure sensors, a getter is used on the front side to provide the required vacuum after the device is sealed, and the vacuum can be maintained for a long time to ensure the life, stability and reliability of the device. At the back side, a mass block structure is left at the varistor to optimize the nonlinear error of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 A schematic diagram of a process for preparing a high-reliability pressure sensor according to an embodiment of the present disclosure;
[0030] Figure 2-Figure 14 The present invention is a schematic structural flow chart of a method for preparing a high-reliability pressure sensor according to an embodiment of the present invention.
[0031] In the figure, 1, substrate; 2, oxide layer; 3, device layer; 4, varistor; 5, polysilicon layer; 6, metal lead; 7, glass sheet; 8, vacuum cavity; 9, vacuum absorber; 11, back cavity; 21, cavity; 22, mass block; 51, pressure-sensitive area; 52, contact hole; 71, groove. DETAILED DESCRIPTION
[0032] In order to enable those skilled in the art to better understand the technical solution of the present disclosure, the present disclosure is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0033] The following is a further detailed description of the implementation methods of the present application in conjunction with the accompanying drawings and examples. The detailed descriptions and drawings of the following examples are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments. In the description of the present application, it should be noted that, unless otherwise specified, the meaning of "multiple" is more than two; the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not vertical in the strict sense, but within the error tolerance range. "Parallel" is not parallel in the strict sense, but within the error tolerance range.
[0034] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.
[0035] like Figure 1-11 As shown, a method for preparing a high-reliability pressure sensor comprises:
[0036] S101 . Provide a substrate 1 .
[0037] refer to Figure 2 In some embodiments, the substrate 1 is an N-type silicon substrate 1 with a thickness of 300um to 600um.
[0038] In a specific example, the thickness of the substrate 1 is 300 um.
[0039] In another specific example, the thickness of the substrate 1 is 600 um.
[0040] In another specific example, the thickness of the substrate 1 is 500 um.
[0041] S102 , forming an oxide layer 2 on the front surface of the substrate 1 .
[0042] refer to Figure 3 In some embodiments, the material of the oxide layer 2 includes silicon oxide (SiO2), wherein the silicon oxide layer 2 is grown on the front side of the substrate 1 by a thermal oxidation process. Specifically, the silicon oxide layer 2 is grown on the front side of the substrate 1 to have a thickness of 200 to 500 nm.
[0043] In a specific example, a silicon oxide layer 2 with a thickness of 200 nm is grown on the front surface of the substrate 1 .
[0044] In another specific example, a silicon oxide layer 2 with a thickness of 500 nm is grown on the front surface of the substrate 1 .
[0045] In another specific example, a silicon oxide layer 2 with a thickness of 400 nm is grown on the front surface of the substrate 1 .
[0046] Specifically, the front side of the substrate 1 is cleaned before growth, and after cleaning, the substrate 1 is placed on a workbench of an oxidation furnace, and subjected to dry oxygen oxidation or wet oxygen oxidation treatment to grow a 200-500 nm silicon oxide layer 2 on the front side of the substrate 1 .
[0047] S103 , patterning and etching the oxide layer 2 to form a cavity 21 exposing the front side of the substrate 1 and a mass block 22 by using an etching process.
[0048] refer to Figure 4 In some embodiments, an ion beam etching process (IBE) is used to pattern and etch the oxide layer 2 to form a cavity 21 exposing the front side of the substrate 1 and a mass block 22 .
[0049] In a specific example, a photoresist layer is spin-coated on the oxide layer 2, and a region to be etched is defined on the photoresist layer by photolithography to form a mask pattern. The mask pattern is etched using an IBE device to transfer the mask pattern to the oxide layer 2 to complete the etching. Finally, the remaining photoresist is cleaned to obtain a layer structure having a cavity 21 and a mass block 22.
[0050] In another specific example, a hard mask is deposited on the oxide layer 2, and a region to be etched is defined on the hard mask by photolithography to form a mask pattern. The mask pattern is etched using an IBE device to transfer the mask pattern to the oxide layer 2 to complete the etching. Finally, the remaining hard mask is cleaned to obtain a layer structure having a cavity 21 and a mass block 22.
[0051] Specifically, Figure 4 As shown, after etching, four spaced masses 22 and three spaced cavities 21 are formed on the front side of the substrate 1 .
[0052] S104 , forming a device layer 3 covering the mass block 22 and the cavity 21 on the surface of the mass block 22 .
[0053] refer to Figure 5 In some embodiments, a bonding process is used to bond the device layer 3 to the front side of the mass block 22. In a direction perpendicular to the front side of the substrate 1, the projection of the device layer 3 covers the projection of the substrate 1. It can be understood that the front side of the mass block 22 is the surface of the mass block 22 facing away from the substrate 1.
[0054] In some embodiments, after forming the device layer 3 covering the mass block 22 and the cavity 21 on the surface of the mass block 22 , the process further includes: performing a chemical mechanical polishing (CMP) thinning process on the device layer 3 .
[0055] In some embodiments, the device layer 3 is thinned to 10-30 um by using a chemical mechanical polishing process.
[0056] In a specific example, the device layer 3 is thinned to 10 um using a chemical mechanical polishing process.
[0057] In another specific example, the device layer 3 is thinned to 30 um by using a chemical mechanical polishing process.
[0058] In another specific example, the device layer 3 is thinned to 20 um by using a chemical mechanical polishing process.
[0059] In the present invention, the device layer 3 and the mass block 22 are bonded by a bonding process, and the thickness of the pressure-sensitive film is precisely controlled by CMP thinning.
[0060] S105 , performing ion implantation on the front surface of the device layer 3 to form a varistor 4 corresponding to the mass block 22 .
[0061] refer to Figure 6 In some embodiments, P-type doping or N-type doping is used for ion implantation to form a varistor 4 on the device layer 3 .
[0062] In a specific example, there are two varistors 4 , and each of the two varistors 4 corresponds to a mass block 22 .
[0063] S106 , forming a polysilicon layer 5 covering the device layer 3 and the varistor 4 on the front side of the device layer 3 , wherein the polysilicon layer 5 has a varistor region 51 corresponding to the varistor 4 .
[0064] refer to Figure 7 In some embodiments, a polysilicon layer 5 covering the device layer 3 and the varistor 4 is formed on the front side of the device layer 3 by a chemical vapor deposition (CVD) process. It can be understood that the front side of the device layer 3 is the surface of the device layer 3 facing away from the substrate 1. In the direction perpendicular to the front side of the substrate 1, the projection of the polysilicon layer 5 covering the substrate 1 is formed.
[0065] In some embodiments, a chemical vapor deposition process is used to form a polysilicon layer 5 with a square resistance of 30-50Ω / □.
[0066] In a specific example, a chemical vapor deposition process is used to form a polysilicon layer 5 with a square resistance of 30Ω / □.
[0067] In another specific example, a chemical vapor deposition process is used to form a polysilicon layer 5 with a square resistance of 50Ω / □.
[0068] In another specific example, a chemical vapor deposition process is used to form a polysilicon layer 5 with a square resistance of 40Ω / □.
[0069] S107 , etching the polysilicon layer 5 to form a contact hole 52 around the pressure-sensitive region 51 to expose the surface of the device layer 3 .
[0070] refer to Figure 8In some embodiments, an ion beam etching (IBE) process is used to form a contact hole 52 exposing the surface of the device layer 3 on the periphery of the varistor region 51. Further, the contact hole 52 is formed at the edge of the polysilicon layer 5 and surrounds the periphery of the varistor region 51. In a direction perpendicular to the front surface of the substrate 1, the projection of the varistor region 51 covers the projection of the varistor 4, wherein the varistor region 51 and the device layer 3 together constitute a varistor film.
[0071] S108 , forming a metal lead 6 in the contact hole 52 .
[0072] refer to Fig. 9 In some embodiments, a magnetron sputtering process is used to form a metal lead 6 in the contact hole 52 , and the metal lead 6 is electrically connected to the device layer 3 .
[0073] In some embodiments, the material of the metal lead 6 includes aluminum. It is understandable that the material of the metal lead 6 includes but is not limited to aluminum, and may also be other metals.
[0074] Specifically, along the axial direction of the contact hole 52 , the metal lead 6 extends out of the contact hole 52 by a preset distance in a direction away from the substrate 1 .
[0075] In some embodiments, a magnetron sputtering process is used to form a metal lead 6 with a thickness of 1-2 um in the contact hole 52 .
[0076] In a specific example, a magnetron sputtering process is used to form a metal lead 6 with a thickness of 1 um in the contact hole 52 .
[0077] In another specific example, a magnetron sputtering process is used to form a metal lead 6 with a thickness of 2 um in the contact hole 52 .
[0078] In another specific example, a magnetron sputtering process is used to form a metal lead 6 with a thickness of 1.5 um in the contact hole 52 .
[0079] S109, performing back etching on the back side of the substrate 1 by using an inductively coupled plasma etching (ICP) process, and stopping at the mass block 22 and the device layer 3, so as to form a back cavity 11 (Cavity) connected to the cavity 21 and used for pressure injection.
[0080] refer to Fig.10 Specifically, after back etching is performed on the back side of the substrate 1, the back side of the device layer 3 and the mass block 22 are exposed.
[0081] S110, bonding the glass sheet 7 with the groove 71 to the pressure-sensitive area 51 using a bonding process to complete the preparation.
[0082] refer to Fig.11 In some embodiments, after the glass sheet 7 is bonded to the pressure-sensitive area 51, the groove 71 and the polysilicon layer 5 enclose a vacuum cavity 8 in the pressure-sensitive area 51. Before the glass sheet 7 having the groove 71 is bonded to the pressure-sensitive area 51 by a bonding process, it also includes: arranging a vacuum getter in the groove 71. In some embodiments, the vacuum getter includes metal titanium, silver or palladium, and is used to maintain the vacuum environment in the vacuum cavity 8.
[0083] In some embodiments, the glass sheet 7 having the groove 71 is bonded to the pressure-sensitive area 51 using an anodic bonding process.
[0084] In the present invention, the ICP process of etching the Cavity (back cavity 11) on the back of the substrate 1 is adopted. Compared with the traditional Cavity-SOI process, the size and thickness of the pressure-sensitive film (also called strain film) can be accurately controlled, and the preparation of a low-thickness pressure-sensitive film with a large back cavity 11 can be achieved, thereby realizing the preparation of a small-range pressure sensor.
[0085] By adopting the back side pressure of the substrate 1, for a small range pressure sensor, a vacuum getter is used on the front side to provide the required vacuum degree in the vacuum chamber 8 after the device is sealed, and the vacuum degree can be maintained for a long time to ensure the life, stability and reliability of the device. At the back side pressure, a mass block 22 is provided at the corresponding position of the varistor 4 to optimize the nonlinear error of the sensor.
[0086] refer to Figure 12-14 In some embodiments, a groove 71 is formed on the back of the glass sheet 7 by laser drilling technology, and a titanium metal layer is plated in the groove 71 by magnetron sputtering process. Specifically, a layer of titanium metal is plated on the bottom of the groove 71. It can be understood that the bottom of the groove is spaced opposite to the pressure sensitive area 51.
[0087] In a specific example, the thickness of the titanium metal layer is 100-500 nm.
[0088] According to a second aspect of an embodiment of the present disclosure, a high-reliability pressure sensor is provided. The sensor is prepared according to the above method.
[0089] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present disclosure, but the present disclosure is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and substance of the present disclosure, and these modifications and improvements are also considered to be within the scope of protection of the present disclosure.
Claims
1. A method for preparing a high-reliability pressure sensor, characterized in that: include: providing a substrate; forming an oxide layer on the front side of the substrate; Using an etching process to pattern the oxide layer to form a cavity exposing the front side of the substrate and a mass block; forming a device layer covering the mass block and the cavity on a surface of the mass block; Performing ion implantation on the front surface of the device layer to form a varistor corresponding to the mass block; forming a polysilicon layer covering the device layer and the varistor on the front side of the device layer, wherein the polysilicon layer has a varistor-sensitive region corresponding to the varistor; Etching the polysilicon layer to form a contact hole exposing the surface of the device layer on the periphery of the pressure-sensitive region; forming a metal lead in the contact hole; Performing back etching on the back side of the substrate by using an inductively coupled plasma etching process, and stopping at the mass block and the device layer, so as to form a back cavity connected to the cavity and used for pressure injection; The glass sheet with the groove is bonded to the pressure-sensitive area by a bonding process to complete the preparation.
2. A method for preparing a high-reliability pressure sensor according to claim 1, characterized in that: After the glass sheet is bonded to the pressure-sensitive area, the groove and the polysilicon layer form a vacuum cavity in the pressure-sensitive area; Before the glass sheet with the groove is bonded to the pressure-sensitive area by the bonding process, the method further includes: arranging a vacuum getter in the groove.
3. A method for preparing a high-reliability pressure sensor according to claim 1 or 2, characterized in that: The material of the oxide layer includes silicon oxide, wherein the silicon oxide layer is grown on the front side of the substrate by using a thermal oxidation process.
4. A method for preparing a high-reliability pressure sensor according to claim 1 or 2, characterized in that: After forming a device layer covering the mass block and the cavity on the surface of the mass block, the method further includes: performing a chemical mechanical polishing and thinning process on the device layer.
5. A method for preparing a high-reliability pressure sensor according to claim 1 or 2, characterized in that: A chemical vapor deposition process is adopted to form a polysilicon layer covering the device layer and the varistor on the front side of the device layer.
6. A method for preparing a high-reliability pressure sensor according to claim 1 or 2, characterized in that: An ion beam etching process is used to form a contact hole exposing the surface of the device layer on the periphery of the pressure-sensitive area.
7. A method for preparing a high-reliability pressure sensor according to claim 1 or 2, characterized in that: A magnetron sputtering process is used to form a metal lead in the contact hole.
8. A method for preparing a high-reliability pressure sensor according to claim 1 or 2, characterized in that: An ion beam etching process is used to pattern and etch the oxide layer to form a cavity exposing the front side of the substrate and a mass block.
9. A method for preparing a high-reliability pressure sensor according to claim 1 or 2, characterized in that: The glass sheet with the groove is bonded to the pressure-sensitive area by using an anodic bonding process.
10. A high reliability pressure sensor, characterized in that: The sensor is prepared according to the method according to any one of claims 1-9.