Mask and piezoresistive pressure sensor
By using a rounded rectangular mask, the problem of poor linearity in piezoresistive pressure sensors was solved, achieving higher measurement accuracy and precision.
Patent Information
- Application Number
- CN202520033712.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-07
- Publication Date
- 2025-12-09
- Estimated Expiration
- 2035-01-07
AI Technical Summary
The linearity of existing piezoresistive pressure sensors is poor, mainly due to the poor linearity of the four sides of the deep cavity made by the mask, which affects the magnitude of resistance change and detection accuracy.
A rounded rectangular mask is used to ensure uniform distribution of etching gas in the mask pattern area. The cavity is formed by etching, which improves the linearity of the four straight edges of the cavity.
The linearity performance of the piezoresistive pressure sensor has been improved, ensuring the accuracy and precision of the measurement.
Smart Images
Figure CN223650023U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of microelectromechanical systems, specifically to a mask and a piezoresistive pressure sensor. Background Technology
[0002] A piezoresistive pressure sensor is a sensor that utilizes the piezoresistive effect and integrated circuit technology. The core component of a piezoresistive pressure sensor is a silicon diaphragm. Part of the silicon diaphragm forms a regular deep cavity, one side of which is connected to the pressure being measured, and the other side is connected to the atmosphere. A Wheatstone bridge is formed by a piezoresistor located above the deep cavity. When an external force is applied to the region containing the deep cavity, the resistance value in the bridge changes, generating a corresponding unbalanced output signal.
[0003] The linearity of the four sides of the deep cavity made using the existing mask is poor. Since the linearity of the four sides of the deep cavity affects the magnitude of the resistance change, the linearity performance of the final piezoresistive pressure sensor is not good. Utility Model Content
[0004] This invention provides a mask and a piezoresistive pressure sensor, aiming to improve the linearity testing performance of the pressure sensor.
[0005] To achieve the above objectives, the embodiments of this utility model adopt the following technical solutions:
[0006] In a first aspect, this application provides a mask, which includes a mask pattern area, and is used to fabricate the cavity of a piezoresistive pressure sensor. The mask pattern area is a rounded rectangle.
[0007] The mask provided in this application is used to fabricate the cavity of a piezoresistive pressure sensor. Since the shape of the mask pattern area is a rounded rectangle, each point of the rounded corner is a smooth point without obvious inflection points or corners. Therefore, during the process of forming the cavity by etching, the etching gas will not accumulate at the rounded corners. Relatively speaking, the etching gas in each part of the mask pattern area is more uniform. As a result, the rate of lateral diffusion of the etching gas is similar, so the linearity of the four straight edges of the cavity is high.
[0008] As one possible implementation, the mask pattern area includes four first straight edges and four first curved edges. The first straight edges are opposite each other in pairs, and the first curved edges are connected to the two adjacent first straight edges.
[0009] As one possible implementation, the four first edges are of the same length.
[0010] As one possible implementation, the distance between two opposite first straight edges is greater than or equal to 500 μm and less than or equal to 2000 μm.
[0011] As one possible implementation, the four first arc edges have the same radius of curvature.
[0012] As one possible implementation, the radius of curvature of the first arc edge is greater than or equal to 50 μm and less than or equal to 150 μm.
[0013] As one possible implementation, the four first arc sides are of equal length.
[0014] Secondly, this application also provides a piezoresistive pressure sensor, which includes a substrate with a cavity. The substrate includes a first surface and a second surface disposed opposite to each other in its thickness direction, and the opening of the cavity is located on the first surface. The projection of the cavity onto the second surface is a rounded rectangle.
[0015] As one possible implementation, the projected shape of the cavity includes four second straight edges and four second curved edges. The second straight edges are opposite each other in pairs, and the second curved edges are connected to the two adjacent second straight edges. The linearity of the second straight edges is less than a set value.
[0016] The beneficial effects of the second aspect and its specific implementation can be referred to the beneficial effects of the first aspect, and will not be repeated here. Attached Figure Description
[0017] Figure 1 A schematic diagram of a photomask pattern provided for an embodiment of this application;
[0018] Figure 2 A schematic diagram of a cavity morphology provided for an embodiment of this application;
[0019] Figure 3 A schematic diagram of another mask pattern provided in an embodiment of this application;
[0020] Figure 4 A schematic diagram illustrating another cavity morphology provided in an embodiment of this application;
[0021] Figure 5 A schematic diagram of a piezoresistive pressure sensor provided in an embodiment of this application;
[0022] Figure 6 This is a schematic diagram of the shape of a cavity projected onto a second surface, as provided in an embodiment of this application. Detailed Implementation
[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0024] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.
[0025] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances. Furthermore, when describing pipelines, the terms "connected" and "linked" in this utility model have the meaning of establishing conductivity. The specific meaning needs to be understood in conjunction with the context.
[0026] In this embodiment of the invention, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" or "for example" in this embodiment of the invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.
[0027] A piezoresistive pressure sensor is a sensor that utilizes the piezoresistive effect and integrated circuit technology. The core component of a piezoresistive pressure sensor is a silicon diaphragm. After photolithography and etching, a portion of the silicon diaphragm is formed into a regular deep cavity (hereinafter referred to as the cavity). One side of the cavity is connected to the pressure being measured, and the other side is connected to the atmosphere. A piezoresistive resistor and corresponding wiring are placed above the cavity, forming a Wheatstone bridge. When an external force is applied to the area containing the cavity, the resistance value in the bridge changes, generating a corresponding unbalanced output signal. By monitoring the output signal, the pressure can be measured.
[0028] The shape of the cavity formed on the silicon film is related to the mask pattern on the mask. The pattern on the mask consists of light-transmitting areas and light-blocking areas. These patterns are transferred to the photoresist through photolithography, and the cavity is formed after exposure, development and etching.
[0029] In a photomask, the light-transmitting areas allow light to pass through and illuminate the photoresist. After exposure, these areas undergo a chemical reaction (for positive photoresist, the exposed areas dissolve during development; for negative photoresist, the exposed areas remain). The light-blocking areas of the photomask block light from reaching the photoresist. Therefore, these areas do not undergo a chemical reaction and remain unchanged (positive photoresist remains, negative photoresist dissolves).
[0030] For example, the mask pattern area on the photomask is a light-transmitting area, meaning the area containing the rounded rectangle is light-transmitting, while the remaining areas on the photomask are opaque. For instance, the material of the mask pattern area is quartz glass, and the material of the remaining areas is chromium. In this case, a positive photoresist is used to transfer the pattern of the mask pattern area. After development, the positive photoresist is dissolved and etched to form the cavity.
[0031] For example, the mask pattern area on the photomask is a light-blocking area, that is, the area containing the rounded rectangle blocks light, while the remaining areas on the photomask are light-transmitting. For example, the material of the mask pattern area is chromium, and the material of the remaining areas is quartz glass. In this case, the pattern of the mask pattern area is transferred using negative photoresist. After development, the negative photoresist is dissolved and etched to form a cavity.
[0032] The purpose of forming a cavity on the silicon diaphragm is to thin the area and make it more sensitive. Since multiple piezoresistors are respectively set on the four straight edges of the cavity, they are the key to the resistance change in the inductive bridge. Therefore, it is necessary to ensure the linearity of the four straight edges of the cavity. If the linearity of the four straight edges is poor, when the cavity is subjected to pressure, the force will be dispersed along the curved surface, and the detection accuracy will be affected.
[0033] Traditional methods for manufacturing piezoresistive pressure sensors include... Figure 1 The mask pattern shown is based on Figure 1 It can be seen that the traditional mask pattern 100 is square. The topographic image of the cavity 200 fabricated using this mask is shown below. Figure 2 As shown. According to Figure 2 It can be seen that the straight edge corresponding to the mask pattern 100 has a curvature, and the reason for the poor linearity is:
[0034] Since the shape transferred from the mask pattern 100 is also square, a large amount of etching gas accumulates at the four right-angle inflection points of the square in the mask pattern 100 during the etching process. Figure 1For example, the etching gas accumulation at position A is relatively large. The etching gas that should have been evenly distributed at positions B and D has partially shifted to position A due to the inflection point. Therefore, the etching gas at positions B and D is relatively small. Positions C and E, being in the central region of the straight edge, are less affected by the inflection point accumulation, resulting in a more even distribution of etching gas. Consequently, the amount of etching gas at positions C and E is greater than that at positions B and D. This leads to a greater diffusion of the etching gas at positions C and E along the direction indicated by the arrow during etching compared to positions B and D. This results in the following pattern: Figure 2 The cavity morphology is shown.
[0035] In view of this, embodiments of this application provide a mask, exemplarily, such as... Figure 3 As shown, the mask includes a mask pattern area 100, which is used to fabricate the cavity of a piezoresistive pressure sensor. The mask pattern area 100 is a rounded rectangle.
[0036] The mask pattern area 100 includes four first straight edges 1 and four first curved edges 2. The first straight edges 1 are opposite each other in pairs, and the first curved edges 2 are connected to the two adjacent first straight edges 1. Since the shape of the mask pattern area 100 is a rounded rectangle, each point of the rounded corner is a smooth point without obvious inflection points or corners. Therefore, during the process of forming the cavity by etching, the etching gas will not accumulate at the rounded corners. Relatively speaking, the etching gas in each part of the mask pattern area 100 is more uniform. Therefore, the rate of lateral diffusion of the etching gas is similar, so the linearity of the four straight edges of the resulting cavity is high.
[0037] Typically, the cavity of a piezoresistive pressure sensor is square; therefore, as Figure 3 As shown, the four first straight edges 1 are of the same length. Based on the size of a conventional piezoresistive pressure sensor cavity, in the mask pattern 100 provided in this application, the distance between two opposite first straight edges is greater than or equal to 500 μm and less than or equal to 2000 μm. For example, the distances between two opposite first straight edges are 500 μm, 1250 μm, and 2000 μm.
[0038] In some embodiments, refer to Figure 3The four first arc-shaped edges 2 have the same radius of curvature. The size of the radius of curvature of the first arc-shaped edge 2 determines the length of the first straight edge 1. When the radius of curvature of the first arc-shaped edge 2 is too small, it is still close to the right-angle inflection point, and the impact of the accumulated etching gas generated during the etching process is still relatively large. When the radius of curvature of the first arc-shaped edge 2 is too large, it will cause the first straight edge 1 to be too short, which will also affect the measurement accuracy. Therefore, the radius of curvature of the first arc-shaped edge 2 of the mask pattern 100 provided in this application embodiment is greater than or equal to 50 μm and less than or equal to 150 μm. For example, the radius of curvature of the first arc-shaped edge 2 is 50 μm, 75 μm, and 150 μm.
[0039] As one possible implementation, the four first arc-shaped sides are of equal length. The equal length of the four first arc-shaped sides ensures the uniformity of the etching gas during the etching process, ensuring that the shape of the cavity obtained after etching meets the process requirements. The straight edges of the cavity are also aligned, guaranteeing the accuracy of the pressure sensor measurements.
[0040] Use inclusion Figure 3 The topographic image of cavity 200 created from the mask pattern shown is as follows: Figure 4 As shown, comparison Figure 2 and Figure 4 It can be seen that the use of including Figure 3 The mask pattern shown shows that the cavity 200 produced has better linearity of straight edges, which better meets the cavity shape requirements and ensures the accuracy of pressure sensor measurements.
[0041] This application also provides a piezoresistive pressure sensor, exemplarily as follows: Figure 5 As shown, the piezoresistive pressure sensor 300 includes a substrate 3, and the substrate 3 has a cavity 4. The substrate 3 includes a first surface 31 and a second surface 32 disposed opposite to each other in its thickness direction, and the opening of the cavity 4 is located on the first surface 31. The shape of the projection of the cavity 4 onto the second surface 32 is a rounded rectangle.
[0042] For example, the shape of the projection of the cavity onto the second surface is as follows: Figure 6 As shown, the projected shape of the cavity includes four second straight edges 5 and four second curved edges 6. The second straight edges 5 are opposite each other in pairs, and the second curved edges 6 are connected to the two adjacent second straight edges 5. The linearity of the second straight edges 5 is less than a set value.
[0043] It is important to note that the set value is the maximum linearity requirement that ensures the measurement accuracy of the piezoresistive pressure sensor.
[0044] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the utility model disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.
[0045] Finally, it should be noted that the above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A photomask, characterized in that, The mask includes a mask pattern area, and the mask is used to fabricate the cavity of the piezoresistive pressure sensor; The shape of the mask pattern area is a rounded rectangle.
2. The photomask according to claim 1, characterized in that, The mask pattern area includes four first straight edges and four first arc edges; the first straight edges are opposite each other in pairs, and the first arc edges are connected to the two adjacent first straight edges.
3. The photomask according to claim 2, characterized in that, The four first straight edges are all the same length.
4. The photomask according to claim 3, characterized in that, The distance between the two opposite first straight edges is greater than or equal to 500 μm and less than or equal to 2000 μm.
5. The photomask according to claim 2, characterized in that, The four first arc edges have the same radius of curvature.
6. The photomask according to claim 5, characterized in that, The radius of curvature of the first arc-shaped edge is greater than or equal to 50 μm and less than or equal to 150 μm.
7. The photomask according to claim 5 or 6, characterized in that, The lengths of the four first arc-shaped sides are equal.
8. A piezoresistive pressure sensor, characterized in that, The piezoresistive pressure sensor includes a substrate, and the substrate has a cavity; the substrate includes a first surface and a second surface disposed opposite to each other in its own thickness direction, and the opening of the cavity is located on the first surface. The shape of the cavity's projection onto the second surface is a rounded rectangle.
9. The piezoresistive pressure sensor according to claim 8, characterized in that, The projected shape of the cavity includes four second straight sides and four second arc-shaped sides; The second straight edges are opposite each other in pairs, and the second arc-shaped edge is connected to the two adjacent second straight edges; The linearity of the second straight edge is less than the set value.