A method for manufacturing a MEMS piezoresistive gauge pressure sensor

Abstract

The application discloses a preparation method of a gauge pressure sensor, and the method comprises the following steps: forming a sacrificial layer on a substrate; forming a pressure-sensitive resistor on the sacrificial layer; forming a pressure-sensitive film on the pressure-sensitive resistor; forming a support layer on the pressure-sensitive film, and forming a cavity penetrating through the thickness of the support layer; and removing the sacrificial layer to release the substrate. The MEMS piezoresistive gauge pressure sensor provided by the embodiment of the application is prepared in a reverse order by introducing the sacrificial layer, so that the ion implantation, diffusion and other process equipment can be effectively avoided.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a method for fabricating a MEMS piezoresistive gauge pressure sensor. Background Technology

[0002] MEMS (Micro-Electro-Mechanical Systems) technology has been widely applied in recent years, demonstrating enormous potential and advantages in fields such as sensors, actuators, and microsystems. Silicon-based MEMS pressure sensors, as an important branch of MEMS sensors, are widely used in automotive electronics, medical equipment, environmental monitoring, aerospace, and other fields due to their advantages such as small size, high precision, fast response speed, and good stability.

[0003] Among them, silicon-based MEMS piezoresistive pressure sensors are an important type of silicon-based MEMS pressure sensors. They obtain pressure information by measuring the change in resistance of a piezoresistive resistor when a silicon diaphragm is deformed under pressure. Traditional silicon-based MEMS piezoresistive gauge pressure sensor chips are mainly based on two process routes: The first route involves forming a piezoresistive resistor through ion implantation or diffusion on the front side, followed by deep silicon etching on the back side to fabricate a pressure-sensitive thin film; the second route involves first fabricating a silicon cup through deep silicon etching, then fabricating a pressure-sensitive thin film through wafer bonding and thinning on the front side, and finally fabricating a piezoresistive resistor through ion implantation or diffusion on the pressure-sensitive thin film.

[0004] Both process routes share some common drawbacks:

[0005] 1. Both processes require the use of ion implantation or diffusion to form varistors. However, ion implantation equipment is expensive, and the uniformity of diffusion is difficult to control, which is not conducive to the process stability or cost control of varistors.

[0006] 2. The sensitivity and size design of the pressure-sensitive film in both processes are entirely based on the performance parameters of silicon material, such as the elastic modulus, which makes it difficult to adapt to some special design requirements;

[0007] 3. Both process routes involve the alignment between the front varistor and the back silicon cup, which is difficult.

[0008] Ensure alignment accuracy. Summary of the Invention

[0009] In view of the above problems, the purpose of this application is to provide a method for fabricating a MEMS piezoresistive gauge pressure sensor.

[0010] According to one aspect of the present invention, a method for fabricating a MEMS piezoresistive gauge pressure sensor is provided, comprising: forming a sacrificial layer on a substrate; forming a piezoresistive resistor on the sacrificial layer; forming a piezoresistive thin film on the piezoresistive resistor; forming a support layer on the piezoresistive thin film, and forming a cavity extending through its thickness in the support layer; and removing the sacrificial layer to release the substrate.

[0011] Optionally, the sacrificial layer is one or more of thermosetting adhesives, metals, and oxides.

[0012] Optionally, the method for forming the varistor includes: forming a varistor layer on the sacrificial layer using a deposition process; and patterning the varistor layer to form a varistor.

[0013] Optionally, the varistor is made of one or more of the following materials: metal oxide, polymer, and coating.

[0014] Optionally, the pressure-sensitive film is formed using a deposition process.

[0015] Optionally, the pressure-sensitive film is made of an insulating material.

[0016] Optionally, the support layer may be one or more of an oxide layer, a nitride layer, or a metal.

[0017] Optionally, at least a portion of the varistor is opposite to the cavity.

[0018] Optionally, before forming the varistor, the method further includes: forming an insulating layer on the sacrificial layer; forming a through-hole in the insulating layer that extends through its thickness; forming a metal layer on the insulating layer, the metal layer covering the surface of the insulating layer and filling the through-hole; patterning the metal layer to form a metal line; and contacting the varistor with the metal line to lead out to the surface of the sacrificial layer via the metal line.

[0019] Optionally, the insulating layer is an oxide layer, a nitrided layer, or a composite stack of an oxide layer and a nitrided layer.

[0020] In this embodiment, by introducing a sacrificial layer, the varistor, varistor film and support layer are all formed by reverse coating. The process involves coating, photolithography and etching, which effectively avoids the use of ion implantation, diffusion and other process equipment.

[0021] Furthermore, since the pressure-sensitive film is formed using a coating process, pressure films with diverse performance parameters can be formed by selecting different materials.

[0022] In a preferred embodiment, to prevent leakage, the pressure-sensitive film is preferably an insulating or high-resistivity material. Attached Figure Description

[0023] The above and other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0024] Figure 1 A flowchart illustrating a method for fabricating a MEMS piezoresistive gauge pressure sensor according to an embodiment of this application is shown;

[0025] Figures 2a to 2h Cross-sectional views of various stages in the fabrication process of the MEMS piezoresistive gauge pressure sensor provided according to embodiments of this application are shown. Detailed Implementation

[0026] The present application will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements are indicated by similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale. Furthermore, some well-known parts may not be shown.

[0027] When describing the structure of a device, when referring to a layer or region as being "above" or "on top of" another layer or region, it can mean that it is directly above another layer or region, or that it contains other layers or regions between it and another layer or region. Furthermore, if the device is flipped, the layer or region will be located "below" or "under" another layer or region.

[0028] To describe a situation where it is located directly on another layer or another area, this article will use the expressions "directly on top of" or "on and adjacent to".

[0029] This application may be presented in various forms, some of which will be described below.

[0030] Figure 1 A flowchart illustrating the fabrication method of a MEMS piezoresistive gauge pressure sensor according to an embodiment of this application is shown, as follows: Figure 1 As shown, the fabrication method of the MEMS piezoresistive gauge pressure sensor includes:

[0031] S110: A sacrificial layer is formed on the substrate;

[0032] S120: A varistor is formed on the sacrificial layer;

[0033] S130: A varistor film is formed on the varistor;

[0034] S140: A support layer is formed on the pressure-sensitive film, and a cavity extending through its thickness is formed in the support layer;

[0035] S150: Remove the sacrificial layer to release the substrate.

[0036] The MEMS piezoresistive gauge pressure sensor provided in this application introduces a sacrificial layer, which allows the entire fabrication process to be completed in reverse order, effectively avoiding processes such as ion implantation and diffusion.

[0037] Figures 2a to 2h Cross-sectional views of various stages in the fabrication process of the MEMS piezoresistive gauge pressure sensor according to embodiments of this application are shown below. Figures 2a to 2h The fabrication method of MEMS piezoresistive gauge pressure sensor is described in detail.

[0038] like Figure 2a As shown, a sacrificial layer 120 is formed on the first surface of the substrate 110.

[0039] In this step, a sacrificial layer 120 is formed on the substrate 110, for example, by spin coating or deposition; the sacrificial layer 120 covers the first surface of the substrate 110. The sacrificial layer 120 can be, but is not limited to, a thermosetting adhesive with good leveling properties and solubility in a specific solution, a metal or oxide that can be wet-etched, etc.

[0040] like Figure 2b As shown, an insulating layer 130 is formed on the sacrificial layer 120.

[0041] In this step, for example, PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition) processes are used to form an insulating layer 130 on the surface of the sacrificial layer 120 away from the substrate 110. The insulating layer 130 includes an oxide layer, a nitride layer, or a composite stack of an oxide layer and a nitride layer. In one embodiment, the insulating layer 130 is, for example, SiO2 or SiN. x Or other materials with good insulation, corrosion resistance, and wear resistance.

[0042] like Figure 2c As shown, a through-hole 131 is formed in the insulating layer 130, extending through its thickness.

[0043] In this step, a mask layer is formed on the surface of the insulating layer 130, and the mask layer is patterned using a photolithography process to form an opening for etching via 131 in the mask layer. Then, the insulating layer 130 is etched through the opening of the mask layer to form a via 131 penetrating the insulating layer 130. The via 131 is used for external metal solder joints.

[0044] like Figure 2d As shown, a metal circuit 140 is formed.

[0045] In this step, a metal layer is formed on the insulating layer 130 using, for example, PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition) processes. The metal layer covers the surface of the insulating layer 130 and fills the vias 131. Next, the metal layer is patterned using photolithography and etching processes to form a metal line 140 on the insulating layer 130. The metal line 140 includes a portion located on the insulating layer 130 and a portion filling the vias 131, and the portion located on the insulating layer 130 and the portion filling the vias 131 are connected together.

[0046] like Figure 2e As shown, a 150 varistor is formed.

[0047] In this step, a resistive layer is formed on the insulating layer 130 and the metal line 140 using PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition) processes. A mask layer is formed on the surface of the resistive layer, and the mask layer is patterned using a photolithography process to form openings in the mask layer. Then, the resistive layer is etched through the openings in the mask layer to form a varistor 150. A portion of the varistor 150 covers the metal line 140, and a portion covers the insulating layer 130; that is, at least a portion of the varistor 150 is in contact with the metal line 140.

[0048] The materials for the 150 varistor can be, but are not limited to, metal oxides such as zinc oxide and barium oxide, or polymers and coatings with pressure-sensitive properties.

[0049] like Figure 2f As shown, a pressure-sensitive film 160 is formed.

[0050] In this step, a varistor film 160 is formed using epitaxy, PVD (Physical Vapor Deposition), or CVD (Chemical Vapor Deposition) processes. The varistor film 160 covers an insulating layer 130, a metal circuit 140, and a varistor 150. The varistor film 160 can be made of materials with different elastic moduli depending on the application and measurement range. To prevent leakage, the varistor film 160 is preferably made of insulating or high-resistivity material.

[0051] like Figure 2g As shown, a support layer 170 is formed on the pressure-sensitive film 160, and a cavity 171 penetrating the support layer 170 is formed in the support layer 170.

[0052] In this step, a support layer 170 is formed on the varistor film 160 using PVD (Physical Vapor Deposition) or CVD (Chemical Vapor Deposition) processes. Next, a cavity 171 penetrating the support layer 170 is formed, for example, using photolithography and etching processes. At least a portion of the varistor 150 is opposite the cavity 171.

[0053] like Figure 2h As shown, the sacrificial layer 120 is removed, and the substrate 110 is separated from the insulating layer 130.

[0054] In this step, for example, a wet etching process is used to remove the sacrificial layer 120. After the sacrificial layer 120 is removed, the substrate 110 and the insulating layer 130 are separated from each other. The surface of the insulating layer 130 away from the varistor film 160 and the metal lines 140 filling the vias 131 of the insulating layer 130 are exposed. The metal lines 140 are electrically connected to the varistor 150 for leading out the varistor 150.

[0055] In this embodiment, by introducing a sacrificial layer, the varistor, varistor film and support layer are all formed by reverse coating. The process involves coating, photolithography and etching, which effectively avoids the use of ion implantation, diffusion and other process equipment.

[0056] Furthermore, since the pressure-sensitive film is formed using a coating process, pressure films with diverse performance parameters can be formed by selecting different materials.

[0057] In a preferred embodiment, to prevent leakage, the pressure-sensitive film is preferably an insulating or high-resistivity material.

[0058] As described above, these embodiments of this application do not exhaustively cover all details, nor do they limit the application to merely the specific embodiments described. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to effectively utilize this application and its modifications. This application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for fabricating a MEMS piezoresistive gauge pressure sensor, comprising: A sacrificial layer is formed on the substrate; A varistor is formed on the sacrificial layer; A varistor film is formed on the varistor; A support layer is formed on the pressure-sensitive film, and a cavity extending through its thickness is formed in the support layer; Remove the sacrificial layer to release the substrate.

2. The method according to claim 1, wherein, The sacrificial layer is one or more of thermosetting adhesives, metals, and oxides.

3. The method according to claim 1, wherein, The method for forming the varistor includes: A varistor layer is formed on the sacrificial layer using a deposition process; The varistor layer is patterned to form a varistor.

4. The method according to claim 3, wherein, The varistor is made of one or more of the following materials: metal oxide and polymer.

5. The method according to claim 1, wherein, The pressure-sensitive film is formed using a deposition process.

6. The method according to claim 5, wherein, The pressure-sensitive film is made of insulating material.

7. The method according to any one of claims 1 to 6, wherein, The support layer is made of one or more of the following: oxide layer, nitride layer, and metal.

8. The method according to any one of claims 1 to 6, wherein, At least a portion of the varistor is opposite to the cavity.

9. The method according to any one of claims 1 to 6, wherein, The process before forming the varistor also includes: An insulating layer is formed on the sacrificial layer; A through-hole is formed in the insulating layer, extending through its thickness; A metal layer is formed on the insulating layer, the metal layer covering the surface of the insulating layer and filling the through-hole; The metal layer is patterned to form metal circuitry; The varistor is in contact with the metal line so that it can be led out to the surface of the sacrificial layer via the metal line.

10. The method according to claim 9, wherein, The insulating layer is an oxide layer, a nitrided layer, or a composite stack of an oxide layer and a nitrided layer.

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