Preparation method of MEMS piezoresistive pressure sensor

Abstract

The invention discloses a preparation method of an MEMS piezoresistive pressure sensor. The method comprises the following steps: forming an alignment mark and a cavity on a first surface of a substrate; forming a window extending from the first surface of the pressure-sensitive layer to the interior of the pressure-sensitive layer in the pressure-sensitive layer, wherein the position of the window on the pressure-sensitive layer corresponds to the position of the alignment mark on the substrate; the pressure-sensitive layer is turned over to enable the first surface of the pressure-sensitive layer to face downwards, the first surface of the substrate and the first surface of the pressure-sensitive layer are bonded together, and the windows are opposite to the corresponding alignment marks; the pressure-sensitive layer is thinned to a preset thickness to form a pressure-sensitive thin film, and a window of the pressure-sensitive thin film penetrates through the thickness of the pressure-sensitive thin film to expose the alignment mark on the substrate; the alignment mark is exposed through the window, a piezoresistor is formed on the second surface of the pressure-sensitive film, and the first surface of the pressure-sensitive film is opposite to the second surface of the pressure-sensitive film.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a method for preparing a MEMS piezoresistive pressure sensor. Background Art

[0002] MEMS (micro-electromechanical systems) technology has been widely used in recent years, demonstrating tremendous potential and advantages in fields such as sensors, actuators, and microsystems. Silicon-based MEMS pressure sensors, a key branch of MEMS sensors, are widely used in automotive electronics, medical equipment, environmental monitoring, aerospace, and other fields due to their small size, high precision, fast response, and good stability.

[0003] Silicon-based MEMS piezoresistive pressure sensors are an important type of silicon-based MEMS pressure sensor. They obtain pressure information by measuring the change in resistance of the piezoresistor when the silicon-based diaphragm is compressed and deformed. With the advancement of technology, the performance requirements for silicon-based MEMS piezoresistive pressure chips are becoming increasingly higher, and the optimization of their manufacturing process has become an important research direction.

[0004] The existing manufacturing process for silicon-based MEMS piezoresistive pressure sensors involves forming a cavity in a substrate through deep silicon etching, bonding a pressure-sensitive film to the substrate, and then performing ion implantation or diffusion on the film to create the piezoresistors. However, this process makes it difficult to precisely align the cavity with the piezoresistors on the film. Summary of the Invention

[0005] In view of the above problems, the purpose of the present application is to provide a method for preparing a MEMS piezoresistive pressure sensor to achieve precise alignment of the cavity on the substrate and the piezoresistor on the pressure-sensitive film.

[0006] According to one aspect of the present invention, there is provided a method for preparing a MEMS piezoresistive pressure sensor, comprising: forming an alignment mark and a cavity on a first surface of a substrate; forming a window in a pressure-sensitive layer extending from the first surface of the pressure-sensitive layer toward the interior thereof, wherein a position of the window on the pressure-sensitive layer corresponds to a position of the alignment mark on the substrate; flipping the pressure-sensitive layer so that its first surface faces downward, and bonding the first surface of the substrate and the first surface of the pressure-sensitive layer together, wherein the window is opposite to the corresponding alignment mark; thinning the pressure-sensitive layer to a predetermined thickness to form a pressure-sensitive film, wherein the window of the pressure-sensitive film penetrates the thickness of the pressure-sensitive film to expose the alignment mark on the substrate; and aligning the alignment mark exposed through the window to form a piezoresistor on the second surface of the pressure-sensitive film, wherein the first surface and the second surface of the pressure-sensitive film are opposite.

[0007] Optionally, the opening size of the window is larger than the size of the alignment mark.

[0008] Optionally, the method of thinning the pressure-sensitive layer to a predetermined thickness to form the pressure-sensitive film includes: a first stage, thinning the pressure-sensitive layer until the bottom of the window is removed, and the remaining part of the window passes through the pressure-sensitive film; and a second stage, thinning the pressure-sensitive layer to a predetermined thickness to form a pressure-sensitive film; wherein, the remaining thickness of the pressure-sensitive layer is measured through the window passing through the pressure-sensitive layer to ensure that the pressure-sensitive layer is thinned to the predetermined thickness.

[0009] Optionally, the sidewall of the window forms a fixed angle with the first surface of the piezoelectric film, and the method for measuring the remaining thickness of the piezoelectric film through the window includes: measuring an opening size b of the window on the second surface of the pressure-sensitive film, and obtaining the remaining thickness of the piezoelectric film based on a correspondence between the opening size b of the window on the second surface of the pressure-sensitive film and the remaining thickness h of the pressure-sensitive film; wherein the correspondence between the opening size b of the window on the second surface of the pressure-sensitive film and the remaining thickness h of the pressure-sensitive film is:

[0010] Wherein, h is the remaining thickness of the pressure-sensitive film, a is the opening size of the window on the first surface of the pressure-sensitive film, and b is the opening size of the window on the second surface of the pressure-sensitive film. is a fixed angle between the side wall of the window and the first surface of the piezoelectric film.

[0011] Optionally, during the process of forming the window in the pressure-sensitive film, the crystal orientation of the first surface of the pressure-sensitive film is controlled to control the fixed angle between the sidewall of the window and the first surface of the pressure-sensitive film.

[0012] According to another aspect of the present invention, there is provided a method for preparing a MEMS piezoresistive pressure sensor, comprising: forming a cavity on a first surface of a substrate; forming a window in a pressure-sensitive layer extending from the first surface of the pressure-sensitive layer toward the interior thereof; flipping the pressure-sensitive layer so that its first surface faces downward, and bonding the first surface of the substrate and the first surface of the pressure-sensitive layer together; thinning the pressure-sensitive layer until the bottom of the window is removed, with the remaining portion of the window penetrating the pressure-sensitive film; measuring the remaining thickness of the pressure-sensitive layer through the window penetrating the pressure-sensitive layer, thinning the pressure-sensitive layer to a predetermined thickness, and forming a pressure-sensitive film; and forming a piezoresistor on the second surface of the pressure-sensitive film, wherein the first and second surfaces of the pressure-sensitive film are opposite.

[0013] Optionally, the sidewall of the window forms a fixed angle with the first surface of the piezoelectric film, and the method for measuring the remaining thickness of the piezoelectric film through the window includes: measuring an opening size b of the window on the second surface of the pressure-sensitive film, and obtaining the remaining thickness of the piezoelectric film based on a correspondence between the opening size b of the window on the second surface of the pressure-sensitive film and the remaining thickness h of the pressure-sensitive film; wherein the correspondence between the opening size b of the window on the second surface of the pressure-sensitive film and the remaining thickness h of the pressure-sensitive film is:

[0014] Wherein, h is the remaining thickness of the pressure-sensitive film, a is the opening size of the window on the first surface of the pressure-sensitive film, and b is the opening size of the window on the second surface of the pressure-sensitive film. is a fixed angle between the side wall of the window and the first surface of the piezoelectric film.

[0015] Optionally, during the process of forming the window in the pressure-sensitive film, the crystal orientation of the first surface of the pressure-sensitive film is controlled to control the fixed angle between the sidewall of the window and the first surface of the pressure-sensitive film.

[0016] Optionally, before the substrate and the pressure-sensitive film are bonded together, an alignment mark is formed on the first surface of the substrate. After the pressure-sensitive film is bonded together, the position of the window on the pressure-sensitive layer corresponds to the position of the alignment mark on the substrate.

[0017] Optionally, the opening size of the window is larger than the size of the alignment mark; the window of the pressure-sensitive film penetrates the thickness of the pressure-sensitive film, exposing the alignment mark on the substrate, and the alignment mark exposed through the window is aligned on the second surface of the pressure-sensitive film to form a piezoresistive resistor.

[0018] The preparation method of the MEMS piezoresistive pressure sensor provided in the present application forms a window on the piezoelectric film, and the position of the window on the piezoelectric film corresponds to the position of the alignment mark on the substrate. When the substrate and the piezoelectric film are bonded together, the window is opposite to the corresponding alignment mark, and during the thinning process of the piezoelectric film, the window exposes the alignment mark. The alignment mark realizes precise alignment of the piezoresistor during the process of forming the piezoresistor.

[0019] In the method for preparing a MEMS piezoresistive pressure sensor provided in the present application, the opening size of the window is larger than the size of the alignment mark, so that the alignment mark can be fully exposed.

[0020] In the method for preparing a MEMS piezoresistive pressure sensor provided in the present application, the depth of the window is greater than the predetermined thickness of the pressure-sensitive film to ensure that the pressure-sensitive film has not been thinned to the predetermined thickness when the bottom of the window is removed.

[0021] The method for preparing the MEMS piezoresistive pressure sensor provided in the present application measures the remaining thickness of the pressure-sensitive film through the window of the pressure-sensitive film to ensure the accuracy of the thickness of the pressure-sensitive film. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and other objects, features and advantages of the present application will become more apparent through the following description of the embodiments of the present application with reference to the accompanying drawings, in which:

[0023] Figure 1a A schematic structural diagram of a MEMS piezoresistive pressure sensor provided in an embodiment of the application is shown;

[0024] Figure 1b Shown Figure 1a Cross-section along the AA direction;

[0025] Figures 2a to 2g shows cross-sectional views of various stages in the preparation process of a MEMS piezoresistive pressure sensor provided in an embodiment of the present application;

[0026] Figure 3 The corresponding relationship between the opening size of the window on the second surface of the pressure-sensitive film and the remaining thickness of the pressure-sensitive film is shown. DETAILED DESCRIPTION

[0027] The present application will be described in more detail below with reference to the accompanying drawings. In each of the drawings, identical elements are represented by similar reference numerals. For the sake of clarity, the various parts in the drawings are not drawn to scale. In addition, some well-known parts may not be shown.

[0028] When describing the structure of a device, when a layer or region is referred to as being "on" or "over" another layer or region, it may mean that the layer or region is directly above the other layer or region, or that other layers or regions are included between the layer or region and the other layer or region. Furthermore, if the device is turned over, the layer or region will be "below" or "beneath" the other layer or region.

[0029] If the purpose is to describe the situation of being directly on another layer or another area, this article will use the expression "directly on..." or "above and adjacent to...".

[0030] This application may be embodied in various forms, some examples of which are described below.

[0031] Figure 1aThe structure diagram of the MEMS piezoresistive pressure sensor provided by the embodiment of the application is shown. Figure 1b Shown Figure 1a Cross-sectional view along the AA direction, wherein, in order to Figure 1a and Figure 1b As shown, the sensor 10 includes a substrate 110 , a pressure-sensitive film 120 a located on a first surface of the substrate 110 , and a piezoresistor 130 located in the pressure-sensitive film 120 a .

[0032] The substrate 110 includes an alignment mark 111 located on a first surface of the substrate 110 , and a cavity 112 extending from the first surface of the substrate 110 toward the interior thereof.

[0033] A pressure-sensitive film 120a is located on the first surface of the substrate 110 and covers the cavity 112. The pressure-sensitive film 120a includes a window 121 extending through its thickness. The window 121 is located over the corresponding alignment mark 111 and exposes the corresponding alignment mark 111 on the substrate 110. The opening of the window 121 is larger than the size of the alignment mark 111, allowing the alignment mark 111 to be fully exposed. A dielectric layer 113 is also located between the substrate 110 and the pressure-sensitive film 120a.

[0034] The piezoresistor 130 is located in the piezoresistive film 120a and is exposed on the second surface of the piezoresistive film 120a, wherein the first surface and the second surface of the piezoresistive film 120a are opposite to each other. At least a portion of the piezoresistive resistor 130 is located above the cavity 112. In one embodiment, the piezoresistive resistor 130 includes a first resistor R1 and a second resistor R2, wherein the first resistor R1 is located above the first side of the cavity 112, and the second resistor R2 is located above the second side of the cavity 112. The first resistor R1 and the second resistor R2 both extend in a first direction, wherein the first side and the second side of the cavity are adjacent. When pressure acts on the piezoresistive film 120a, the piezoresistive film 120a above the cavity 112 deforms, causing the resistance values ​​of the first resistor R1 and the second resistor R2 to change, and the changes in the resistance value of the first resistor R1 and the resistance value of the second resistor R2 are opposite.

[0035] The sensor 10 also includes a heavily doped region 14, an insulating layer 150, and a lead structure 142. The heavily doped region 141 is located in the pressure-sensitive film 120a and is exposed on the second surface of the pressure-sensitive film 120a. The heavily doped region 141 penetrates the piezoresistor 130, meaning that the piezoresistor 130 and the heavily doped region 141 are adjacent to each other. The sensor 10 also includes an insulating layer 150, which covers at least the exposed surface of the pressure-sensitive film 120a and the exposed surface of the substrate 110. The lead structure 142 is located on the insulating layer 150 on the second surface of the pressure-sensitive film 120a and penetrates the insulating layer 150 to contact the heavily doped region 141. The lead structure 142 contacts the piezoresistor 130 and the pressure-sensitive film 120a via the heavily doped region 131. The piezoresistor 130 is connected to an external bridge via the lead structure 142. Changes in the bridge voltage reflect changes in the resistance of the piezoresistor. By measuring the output voltage of the bridge, the pressure applied to the sensor 10 is measured.

[0036] Figures 2a to 2g The cross-sectional views at various stages of the preparation process of the MEMS piezoresistive pressure sensor provided in accordance with an embodiment of the present application are shown.

[0037] like Figure 2a As shown, an alignment mark 111 is formed on the first surface of the substrate 110 .

[0038] In this step, alignment marks 111 are formed on the first surface of substrate 110 using, for example, photolithography and etching processes. Etching can be performed using dry etching and / or wet etching. Dry etching methods include ion milling, plasma etching, reactive ion etching, laser ablation, and the like. Preferably, substrate 110 can be a semiconductor substrate. More preferably, substrate 110 can be a silicon substrate, for example.

[0039] Next, a dielectric layer 113 is formed. Dielectric layer 113 is, for example, an oxide layer. In one embodiment, the dielectric layer is, for example, a SiO2 layer. Dielectric layer 113 covers all surfaces of substrate 110, that is, dielectric layer 113 completely covers substrate 110. For example, dielectric layer 113 is formed on the surface of substrate 110 using a thermal oxidation process, such as hydrothermal oxidation (HTO) or selective reactive oxidation (SRO).

[0040] like Figure 2b As shown, for example, photolithography and dry etching and / or wet etching processes are used to form a cavity 112 that penetrates the dielectric layer 113 on the first surface of the substrate 110 and extends into the interior of the substrate 110. That is, the cavity 112 extends from the dielectric layer 113 on the first surface of the substrate 110 toward the substrate 110 and terminates inside the substrate 110. During the formation of the cavity 112, the lateral position of the cavity 112 on the substrate 110 is determined by the alignment mark 111.

[0041] like Figure 2c As shown, a window 121 is formed on the first surface of the pressure-sensitive layer 120 .

[0042] In this step, for example, a mask layer is formed on the first surface of the pressure-sensitive layer 120, and the mask layer is patterned using a photolithography process to form an opening in the mask layer. The first surface of the pressure-sensitive layer 120 is then etched through the patterned mask layer to form a window 121 extending from the first surface to the interior of the pressure-sensitive layer 120. The window 121 is formed using dry etching and / or wet etching, and can be either isotropic or anisotropic etching.

[0043] The position of the window 121 on the pressure-sensitive layer 120 corresponds to the position of the alignment mark 111 on the substrate 110 , so that when the first surface of the substrate 110 and the first surface of the pressure-sensitive layer 120 are bonded, the window 121 and the corresponding alignment mark 111 are aligned.

[0044] Furthermore, the opening size a of the window 121 on the first surface of the pressure-sensitive layer 120 is controlled by controlling the opening size of the mask layer, and the window 121 is controlled to reach a predetermined depth h1 by controlling the etching rate and etching time. The sidewalls of the window 121 are perpendicular to the first surface of the pressure-sensitive layer 120, or the sidewalls of the window 121 are inclined relative to the first surface of the pressure-sensitive layer 120, and a fixed angle is formed between the sidewalls of the window 121 and the first surface of the pressure-sensitive layer 120. .

[0045] In one embodiment, by controlling the crystal orientation of the first surface of the pressure-sensitive layer 120, the sidewall of the window 121 is controlled to be inclined relative to the first surface of the pressure-sensitive layer 120, and a fixed angle is formed between the sidewall of the window 121 and the first surface of the pressure-sensitive layer 120. Specifically, the pressure-sensitive layer 120 is, for example, a silicon substrate, and the crystal orientation of the first surface of the pressure-sensitive layer 120 is (110). The window 121 is formed by wet etching, and the etching liquid is, for example, a heated KOH solution. Etching is performed from the first surface of the pressure-sensitive layer 120 to the inside of the pressure-sensitive layer 120. Since the etching rate of the (100) crystal plane of the pressure-sensitive layer 120 is higher than that of its (111) crystal plane, the etching surface can be etched along an etching angle of 54.74° to form a side wall inclined relative to the first surface of the pressure-sensitive layer 120, that is, =54.74°.

[0046] like Figure 2d As shown, the pressure-sensitive layer 120 is flipped over so that the first surface of the pressure-sensitive layer 120 faces downward, and the first surface of the substrate 110 and the first surface of the pressure-sensitive layer 120 are bonded together, wherein the window 121 and the corresponding alignment mark 111 are aligned.

[0047] Next, the pressure-sensitive layer 120 is thinned to a predetermined thickness.

[0048] In this step, thinning starts from the second surface of the pressure-sensitive layer 120 , that is, thinning starts from the surface of the pressure-sensitive layer 120 away from the substrate 110 . The thinning process includes a first stage and a second stage.

[0049] In the first stage, the pressure-sensitive layer 120 is thinned until the bottom of the window 121 is removed, so that the window 121 extends through the thickness of the pressure-sensitive layer 120 and exposes the corresponding alignment mark 111 on the substrate 110. The depth h1 of the window 121 is greater than the predetermined thickness h0 of the pressure-sensitive layer 120 to ensure that the pressure-sensitive layer 120 has not been thinned to the predetermined thickness h0 when the bottom of the window 121 is removed.

[0050] In the second stage, the pressure-sensitive layer 120 is thinned to a predetermined thickness h0 to form a pressure-sensitive film 120a. During this process, the remaining thickness of the pressure-sensitive layer 120 is measured through the window 121 of the pressure-sensitive layer 120 to ensure the accuracy of the thickness of the pressure-sensitive layer 120.

[0051] When the sidewall of the window 121 is perpendicular to the first surface of the pressure-sensitive layer 120 , the remaining film thickness h of the pressure-sensitive layer 120 can be directly measured by a step profiler.

[0052] When the side wall of the window 121 is inclined relative to the first surface of the pressure-sensitive layer 120, the thickness h of the pressure-sensitive layer 120 is controlled by controlling the opening size b of the window 121 on the second surface of the pressure-sensitive layer 120 (that is, the surface of the pressure-sensitive layer 120 away from the substrate 110), so that the pressure-sensitive layer 120 is thinned to a predetermined thickness h0.

[0053] Specifically, first obtain the corresponding relationship between the opening size b of the window 121 on the second surface of the pressure-sensitive layer 120 and the thickness h of the pressure-sensitive layer 120. Figure 3 As shown, the opening size of the window 121 on the first surface of the pressure-sensitive layer 120 is a, the opening size of the window 121 on the second surface of the pressure-sensitive layer 120 (i.e., the surface of the pressure-sensitive layer 120 away from the substrate 110) is b, and the angle between the sidewall of the window 121 and its first surface is , the thickness of the pressure-sensitive layer 120 is h, the opening size of the window 121 on the second surface of the pressure-sensitive layer 120 is b, and the corresponding relationship between the thickness h of the pressure-sensitive layer 120 is:

[0054] Next, the opening size of the window 121 on the second surface of the pressure-sensitive layer 120 (i.e., the surface of the pressure-sensitive layer 120 away from the substrate 110) is measured, and the thickness h of the pressure-sensitive layer 120 is obtained through the correspondence between the opening size b of the window 121 on the second surface of the pressure-sensitive layer 120 and the thickness h of the pressure-sensitive layer 120, so that the pressure-sensitive layer 120 is thinned to a predetermined thickness h0.

[0055] It is worth noting that after the pressure-sensitive layer 120 is thinned to a predetermined thickness to form a pressure-sensitive film 120 a , an oxide layer 122 is formed on the surface of the pressure-sensitive film 120 a . The oxide layer 122 conformally covers the surface of the pressure-sensitive film 120 a and the sidewalls of the window 121 .

[0056] like Figure 2e As shown, a varistor 130 and a heavily doped region 123 are formed in the pressure-sensitive film 120 a.

[0057] In this step, the oxide layer 122 on the surface of the pressure-sensitive film 120 a and the dielectric layer 113 exposed by the window 121 are first removed to completely expose the alignment mark 111 .

[0058] Next, for example, a first mask is formed on the pressure-sensitive film 120a, and the first mask is patterned using photolithography to form an opening in the first mask. Ions are then implanted into the pressure-sensitive film 120a through the opening in the first mask to form a shallowly doped region, i.e., the varistor 130. Next, a second mask is formed on the pressure-sensitive film 120a, and the second mask is patterned using photolithography to form an opening in the second mask. Ions are then implanted into the pressure-sensitive film 120a through the opening in the second mask to form a heavily doped region 141. The heavily doped region 141 penetrates the varistor 130.

[0059] During the photolithography of the first mask and the second mask, the alignment mark 111 exposed through the window 121 is aligned to achieve precise alignment of the varistor 130 and the cavity 112 on the substrate 110 , as well as precise alignment of the heavily doped region 141 and the varistor 130 .

[0060] like Figure 2f As shown, an insulating layer 150 is formed.

[0061] In this step, the insulating layer 150 is formed by, for example, using a PECVD (Plasma Enhanced Chemical Vapor Deposition) or LPCVD (Low Pressure Chemical Vapor Deposition) process. The insulating layer 150 covers at least the surface of the pressure-sensitive film 120a away from the substrate 110. In this embodiment, the insulating layer 150 covers, for example, the exposed surface of the pressure-sensitive film 120a and the exposed surface of the substrate 110. The insulating layer 150 is, for example, an oxide layer (e.g., a SiO2 layer), a nitride layer (e.g., a SiN x layer) or oxynitride layer (such as SiO x N y layer) or a composite layer of any of the above insulating layers.

[0062] Next, a through hole 151 is formed in the insulating layer 150 on the second surface of the pressure-sensitive film 120 a by, for example, using a photolithography and etching process. The through hole 151 exposes the surface of the heavily doped region 141 .

[0063] like Figure 2g As shown, a lead structure 142 is formed.

[0064] In this step, a metal layer is formed on the insulating layer 150 on the second surface of the pressure-sensitive film 120a using methods such as magnetron sputtering, vapor deposition, and electron beam evaporation. The metal layer covers the insulating layer 150 on the second surface of the pressure-sensitive film 120a and fills the through-holes 151 in the insulating layer 150. Next, the metal layer is etched using, for example, photolithography and etching processes to form the lead structure 142. The lead structure 142 is located on the insulating layer 150 on the second surface of the pressure-sensitive film 120a and penetrates the insulating layer 150 to contact the heavily doped region 141.

[0065] Although Figure 2g Only one layer of lead structure 142 is shown in the figure, but it should be understood that in other embodiments, multiple layers of lead structure 142 may be included to ensure ohmic contact and welding reliability.

[0066] The preparation method of the MEMS piezoresistive pressure sensor provided in the present application forms a window on the piezoelectric film, and the position of the window on the piezoelectric film corresponds to the position of the alignment mark on the substrate. When the substrate and the piezoelectric film are bonded together, the window is opposite to the corresponding alignment mark, and during the thinning process of the piezoelectric film, the window exposes the alignment mark. The alignment mark realizes precise alignment of the piezoresistor during the process of forming the piezoresistor.

[0067] In the method for preparing a MEMS piezoresistive pressure sensor provided in the present application, the opening size of the window is larger than the size of the alignment mark, so that the alignment mark can be fully exposed.

[0068] The preparation method of the MEMS piezoresistive pressure sensor provided in the present application measures the remaining thickness of the pressure-sensitive film through the window of the pressure-sensitive film to ensure the accuracy of the thickness of the pressure-sensitive film. In addition, the number of windows and the number of alignment marks may be different. The alignment marks are preferably located on the periphery of the substrate, and the windows can be located on the periphery of the substrate or in the middle area of ​​the substrate. Some or all of the windows can also be precisely aligned with the alignment marks.

[0069] While the embodiments of the present application are described above, these embodiments do not exhaustively describe all details, nor do they limit the present application to the specific embodiments described. Clearly, numerous modifications and variations are possible based on the above description. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present application, thereby enabling those skilled in the art to better utilize the present application and its modifications. The present application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a MEMS piezoresistive pressure sensor, comprising: forming an alignment mark and a cavity on the first surface of the substrate; forming a window in the pressure-sensitive layer, the window extending from the first surface of the pressure-sensitive layer toward the interior thereof, wherein a position of the window on the pressure-sensitive layer corresponds to a position of the alignment mark on the substrate; flipping the pressure-sensitive layer so that its first surface faces downward, and bonding the first surface of the substrate and the first surface of the pressure-sensitive layer together, wherein the window is opposite to the corresponding alignment mark; Thinning the pressure-sensitive layer to a predetermined thickness to form a pressure-sensitive film, wherein a window of the pressure-sensitive film penetrates the thickness of the pressure-sensitive film to expose the alignment mark on the substrate; and The alignment marks exposed through the window are aligned to form a pressure-sensitive resistor on the second surface of the pressure-sensitive film, wherein the first surface and the second surface of the pressure-sensitive film are opposite to each other.

2. The method according to claim 1, wherein The opening size of the window is larger than the size of the alignment mark.

3. The method according to claim 1, wherein The method of thinning the pressure-sensitive layer to a predetermined thickness to form the pressure-sensitive film comprises: In a first stage, the pressure-sensitive layer is thinned until the bottom of the window is removed, and the remaining portion of the window penetrates the pressure-sensitive film; and In the second stage, the pressure-sensitive layer is thinned to a predetermined thickness to form a pressure-sensitive film; The remaining thickness of the pressure-sensitive layer is measured through a window penetrating the pressure-sensitive layer to ensure that the pressure-sensitive layer is thinned to a predetermined thickness.

4. The method according to claim 3, wherein: The sidewall of the window forms a fixed angle with the first surface of the piezoelectric film, and the method for measuring the remaining thickness of the piezoelectric film through the window includes: Measuring an opening size b of the window on the second surface of the pressure-sensitive film, and obtaining the remaining thickness of the piezoelectric film based on a correspondence between the opening size b of the window on the second surface of the pressure-sensitive film and the remaining thickness h of the pressure-sensitive film; The corresponding relationship between the opening size b of the window on the second surface of the pressure-sensitive film and the remaining thickness h of the pressure-sensitive film is: Wherein, h is the remaining thickness of the pressure-sensitive film, a is the opening size of the window on the first surface of the pressure-sensitive film, and b is the opening size of the window on the second surface of the pressure-sensitive film. is a fixed angle between the side wall of the window and the first surface of the piezoelectric film.

5. The method according to claim 3, wherein: During the process of forming the window in the pressure-sensitive film, the crystal orientation of the first surface of the pressure-sensitive film is controlled to control the fixed angle between the sidewall of the window and the first surface of the pressure-sensitive film.

6. A method for preparing a MEMS piezoresistive pressure sensor, comprising: forming a cavity on the first surface of the substrate; forming a window in the pressure-sensitive layer extending from the first surface of the pressure-sensitive layer toward the interior thereof; flipping the pressure-sensitive layer so that its first surface faces downward, and bonding the first surface of the substrate and the first surface of the pressure-sensitive layer together; thinning the pressure-sensitive layer until the bottom of the window is removed, with the remaining portion of the window penetrating the pressure-sensitive film; measuring the remaining thickness of the pressure-sensitive layer through a window penetrating the pressure-sensitive layer, and thinning the pressure-sensitive layer to a predetermined thickness to form a pressure-sensitive film; as well as A varistor is formed on the second surface of the pressure-sensitive film, wherein the first surface and the second surface of the pressure-sensitive film are opposite to each other.

7. The method according to claim 6, wherein: The sidewall of the window forms a fixed angle with the first surface of the piezoelectric film, and the method for measuring the remaining thickness of the piezoelectric film through the window includes: Measuring an opening size b of the window on the second surface of the pressure-sensitive film, and obtaining the remaining thickness of the piezoelectric film based on a correspondence between the opening size b of the window on the second surface of the pressure-sensitive film and the remaining thickness h of the pressure-sensitive film; The corresponding relationship between the opening size b of the window on the second surface of the pressure-sensitive film and the remaining thickness h of the pressure-sensitive film is: Wherein, h is the remaining thickness of the pressure-sensitive film, a is the opening size of the window on the first surface of the pressure-sensitive film, and b is the opening size of the window on the second surface of the pressure-sensitive film. is a fixed angle between the side wall of the window and the first surface of the piezoelectric film.

8. The method according to claim 6, wherein: During the process of forming the window in the pressure-sensitive film, the crystal orientation of the first surface of the pressure-sensitive film is controlled to control the fixed angle between the sidewall of the window and the first surface of the pressure-sensitive film.

9. The method according to claim 6, wherein: Before the substrate and the pressure-sensitive film are bonded together, an alignment mark is formed on the first surface of the substrate. After the pressure-sensitive film is bonded together, the position of the window on the pressure-sensitive layer corresponds to the position of the alignment mark on the substrate.

10. The method according to claim 9, wherein: The opening size of the window is larger than the size of the alignment mark; the window of the pressure-sensitive film penetrates the thickness of the pressure-sensitive film, exposing the alignment mark on the substrate, and the alignment mark exposed through the window is aligned on the second surface of the pressure-sensitive film to form a piezoresistive resistor.

Images