Structure, array and fabrication method of variable stiffness cantilever beam sensor

Abstract

This invention discloses a variable stiffness cantilever beam sensor structure, a variable stiffness cantilever beam sensor array, and a method for fabricating the variable stiffness cantilever beam sensor structure. The variable stiffness cantilever beam sensor structure includes a support structure and a cantilever beam structure, with the cantilever beam structure disposed on the support structure. The cantilever beam structure includes a sensing part and a transmitting part arranged sequentially along a direction away from the support structure. The thickness of the sensing part is less than the thickness of the transmitting part, and a piezoresistor is disposed on the sensing part. The variable stiffness cantilever beam sensor structure of this invention, through a variable stiffness structure design—different thicknesses for the transmitting and sensing parts—increases the local stress in the area where the piezoresistor is located under the same external force, thereby improving the sensitivity of the cantilever beam sensor.

Description

Technical Field

[0001] This invention relates to the field of micro-nano equipment and device technology, and in particular to a variable stiffness cantilever beam sensor structure, a variable stiffness cantilever beam sensor array, and a method for fabricating the variable stiffness cantilever beam sensor structure. Background Technology

[0002] Cantilever beam sensors are currently widely used in environmental monitoring, underwater navigation, and micro-force calibration. Ultra-high sensitivity cantilever beam sensors are considered important tools for next-generation physical, chemical, and biological sensing. To develop sensors with higher sensitivity and threshold detection limits, researchers have studied the sensing principles, morphology, geometry, and design principles of biological flow sensors in nature, and fabricated cantilever-type biomimetic beard sensors. However, current fabrication methods for cantilever biomimetic beard sensors mainly focus on 3D printing, inkjet printing, and self-adhesive technologies. These cantilever beams are usually composed of two different materials, and the bonding error between the two materials is relatively large, resulting in poor sensor uniformity and limiting the large-scale production and further application of cantilever biomimetic beard sensors. Microelectromechanical systems (MEMS) technology is a traditional sensor fabrication technology. Cantilever sensors based on MEMS technology have the advantages of easy integration, miniaturization, and mass production. However, current biomimetic MEMS beard sensors based on biomimetic principles mostly have complex fabrication processes, requiring innovative process technologies to fabricate uniform, integrally molded, and highly sensitive cantilever biomimetic sensors.

[0003] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0004] The purpose of this invention is to provide a variable stiffness cantilever beam sensor structure, a variable stiffness cantilever beam sensor array, and a method for manufacturing the variable stiffness cantilever beam sensor structure, which can achieve ultra-sensitive sensing.

[0005] To achieve the above objectives, embodiments of the present invention provide a variable stiffness cantilever beam sensor structure, including a support structure and a cantilever beam structure. The cantilever beam structure is disposed on the support structure. The cantilever beam structure includes a sensing part and a transmitting part arranged sequentially along a direction away from the support structure. The thickness of the sensing part is less than the thickness of the transmitting part. A piezoresistor is disposed on the sensing part.

[0006] In one or more embodiments of the present invention, the sensing part has a first surface parallel to the extension direction of the cantilever beam structure, and the piezoresistor is disposed on the first surface; the transmitting part has a second surface parallel to the extension direction of the cantilever beam structure; the first surface and the second surface are disposed parallel to each other.

[0007] In one or more embodiments of the present invention, the support structure has a third surface parallel to the extension direction of the cantilever beam structure, the third surface being located in the same plane as the first surface; a metal lead is provided on the third surface, the metal lead being connected to the varistor.

[0008] In one or more embodiments of the present invention, the ratio of the thickness of the sensing part to the thickness of the transmitting part is greater than or equal to 1 / 3 and less than 1, preferably, the ratio of the thickness of the sensing part to the thickness of the transmitting part is 1 / 2.

[0009] In one or more embodiments of the present invention, the aspect ratio of the transmission part is 200-800.

[0010] In one or more embodiments of the present invention, the aspect ratio of the transmission part is 400-600.

[0011] In one or more embodiments of the present invention, the support structure, the sensing part of the cantilever beam structure, and the transmission part of the cantilever beam structure are integrally formed.

[0012] An embodiment of the present invention provides a variable stiffness cantilever beam sensor array, including a support structure and multiple sets of cantilever beam structures. The multiple sets of cantilever beam structures are arranged on the support structure. Each set of cantilever beam structures includes a sensing part and a transmitting part arranged sequentially along a direction away from the support structure. The thickness of the sensing part is less than the thickness of the transmitting part. A piezoresistor is provided on the sensing part. In particular, at least one set of cantilever beam structures has a different aspect ratio of the transmitting part than the other cantilever beam structures.

[0013] In one or more embodiments of the present invention, the length-to-diameter ratios of the multiple sets of cantilever beam structure transmission parts are all different.

[0014] In one or more embodiments of the present invention, the sensing part has a first surface parallel to the extension direction of the cantilever beam structure, and the varistor is disposed on the first surface; the transmitting part has a second surface parallel to the extension direction of the cantilever beam structure; the supporting structure has a third surface parallel to the extension direction of the cantilever beam structure, and a metal lead is disposed on the third surface, the metal lead being connected to the varistor; the third surface and the first surface are located in the same plane, and the second surface is disposed parallel to the first surface.

[0015] In one or more embodiments of the present invention, the supporting structure, the sensing part of the multiple sets of cantilever beam structures, and the transmission part are integrally formed.

[0016] Embodiments of the present invention also provide a method for fabricating the above-described variable stiffness cantilever beam sensor structure, comprising: providing a wafer having a first surface and a second surface disposed opposite to each other; forming a cantilever beam structure of the variable stiffness cantilever beam sensor structure on the first surface of the wafer; etching the sensing portion of the cantilever beam structure from the second surface of the wafer, such that its thickness is less than the thickness of the transmitting portion; and disposing a varistor at the sensing portion from the first surface of the wafer.

[0017] In one or more embodiments of the present invention, the step of etching the sensing portion of the cantilever beam structure from the second surface of a wafer includes: providing a mold assembly, the mold assembly including a first mold body and a second mold body, the second mold body having a through-hole formed therethrough; placing and positioning the wafer between the first mold body and the second mold body, wherein the first surface of the wafer is in contact with the first mold body, and the through-hole of the second mold body exposes the sensing portion of the cantilever beam structure; and etching the sensing portion of the cantilever beam structure through the through-hole.

[0018] In one or more embodiments of the present invention, a mold assembly is provided, comprising: providing a first mold body having a first limiting portion formed thereon for limiting a wafer, and a second limiting portion formed thereon for limiting relative to a second mold body; providing a second mold body having a protruding protective portion formed thereon, the protrusion height of the protective portion being less than or equal to the thickness difference between the wafer and the cantilever beam structure; and providing a limiting member cooperating with the second limiting portion to limit relative to the first mold body and the second mold body.

[0019] In one or more embodiments of the present invention, the protrusion height of the protective portion is less than the thickness difference between the wafer and the cantilever beam structure by about 50-100 micrometers.

[0020] In one or more embodiments of the present invention, placing and positioning a wafer between the first mold body and the second mold body includes: attaching a first surface of the wafer to the first mold body and positioning it by the first positioning portion; placing the second mold body on the wafer, wherein the protective portion is provided corresponding to the transmission portion of the cantilever beam structure, and the slot is provided corresponding to the sensing portion of the cantilever beam structure; and the positioning member cooperates with the second positioning portion to position the first mold body and the second mold body.

[0021] In one or more embodiments of the present invention, the shape of the second mold body is the same as the shape of the wafer, and the size of the second mold body is the same as the size of the wafer.

[0022] In one or more embodiments of the present invention, the first limiting part may be a limiting post protruding from the surface of the first mold body or a limiting groove formed on the surface of the first mold body, the second limiting part may be a limiting hole arranged in a circle, the radius of the circle containing the limiting hole is equal to the radius of the wafer, and the limiting member may be a pin or a buckle.

[0023] Compared with the prior art, the variable stiffness cantilever beam sensor structure according to the present invention improves the sensitivity of the cantilever beam sensor by using a variable stiffness structure design—different thicknesses of the transmission part and the sensing part—to increase the local stress in the area where the piezoresistor is located under the same external force.

[0024] The variable stiffness cantilever beam sensor structure according to the embodiments of the present invention is a novel variable stiffness piezoresistive bionic cantilever beam sensor based on MEMS technology, which achieves ultra-sensitive sensing.

[0025] According to an embodiment of the present invention, a variable stiffness cantilever beam sensor array is designed with multiple cantilever beam array structures. By integrating cantilever beam structures with different aspect ratios in the transmission part, the detection limit and sensitivity of the variable stiffness cantilever beam sensor array are increased, thereby improving the performance of the sensor.

[0026] The method for fabricating a variable stiffness cantilever beam sensor structure according to an embodiment of the present invention utilizes MEMS process technology with hard masks to extend the process of locally etching the back side of the cantilever beam structure (the surface corresponding to the first surface of the sensing part), which can ensure the uniformity of the varistor and also enable mass production.

[0027] The method for manufacturing a variable stiffness cantilever beam sensor structure according to an embodiment of the present invention facilitates mass production and improves the yield of wafer fabrication by using specific mold components, and simplifies the process steps. Attached Figure Description

[0028] Figure 1 This is a structural schematic diagram of a variable stiffness cantilever beam sensor structure according to an embodiment of the present invention.

[0029] Figure 2 This is a flowchart of a method for manufacturing a variable stiffness cantilever beam sensor structure according to an embodiment of the present invention;

[0030] Figures 3-6 This is a schematic diagram of the steps in the fabrication method of a variable stiffness cantilever beam sensor structure according to an embodiment of the present invention. Detailed Implementation

[0031] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0032] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0033] As mentioned in the background section, cantilever beam sensors are currently widely used in environmental monitoring, underwater navigation, and micro-force calibration. Ultra-high sensitivity cantilever beam sensors are considered important tools for next-generation physical, chemical, and biological sensing. Cantilever beam sensors have crucial applications in micro-force detection and density detection. Currently, effective methods for improving the sensitivity of cantilever beam sensors are based on biomimetic principles and design. However, most cantilever biomimetic cantilever sensors are fabricated using 3D printing and self-adhesion technologies, making mass production difficult. It is challenging to guarantee uniformity between different batches of devices, and integration is also difficult. Mass production of integrated ultra-sensitive cantilever beam sensors using simple methods remains a significant challenge. Furthermore, current variable stiffness cantilever beam sensors are often manufactured by etching the upper surface of the cantilever beam (the top surface in the sensor's operating state). The etching process increases surface roughness, causing non-uniform resistance values ​​in the varistor and affecting device performance. With the increasing demand for higher sensitivity in cantilever beam sensors, further research and development of high-sensitivity MEMS cantilever beam sensors has become particularly important.

[0034] To address the aforementioned issues, this invention creatively proposes a variable stiffness cantilever beam sensor structure, a variable stiffness cantilever beam sensor array, and a method for fabricating the variable stiffness cantilever beam sensor structure. This method ensures uniformity of the piezoresistive resistors while enabling mass production and achieving ultra-sensitive sensing.

[0035] like Figure 1 As shown, a variable stiffness cantilever beam sensor structure according to an embodiment of the present invention includes a support structure 10 and a cantilever beam structure 20. The cantilever beam structure 20 extends outward from one end of the support structure 10 and is disposed on the support structure 10. The cantilever beam structure 20 includes a sensing part 21 and a transmitting part 22 arranged sequentially in a direction away from the support structure 10. The thickness of the sensing part 21 is less than the thickness of the transmitting part 22, and a piezoresistive resistor 23 is disposed on the sensing part 21.

[0036] For example, the support structure 10 and the cantilever beam structure 20 can be integrally formed. The material of the support structure 10 and the cantilever beam structure 20 is preferably silicon.

[0037] The thickness of the support structure 10 is much greater than the overall thickness of the cantilever beam structure 20. The support structure 10 is mainly used to constrain one end of the cantilever beam structure 20. The support structure 10 has a third surface 101 parallel to the extension direction of the cantilever beam structure 20, and metal leads are provided on the third surface 101.

[0038] The sensing part 21 of the cantilever beam structure 20 has a first surface 211 parallel to the extending direction of the cantilever beam structure 20. A varistor 23 is disposed on the first surface 211 and electrically connected to a metal lead located on the third surface 101. The metal lead is responsible for transmitting the signal sensed by the varistor 23 on the sensing part 21. The first surface 211 of the sensing part 21 and the third surface 101 of the support structure 10 are located in the same plane. The transmitting part 22 of the cantilever beam structure 20 has a second surface 221 parallel to the extending direction of the cantilever beam structure 20. The second surface 221 is arranged parallel to the first surface 211 and the third surface 101 of the support structure 10. Preferably, the second surface 221, the first surface 211, and the third surface 101 of the support structure 10 are located in the same plane. After the first surface 211 of the sensing part 21 and the second surface 221 of the transmission part 22 are on the same plane, a hard mask-based technique can be used to locally etch the back side of the sensing part 21 (the other surface opposite to the first surface 211). This increases the response of the varistor 23 under the same displacement deflection of the cantilever beam structure 20, while maintaining or even improving the stability, consistency and uniformity of the varistor 23 on the first surface 211 of the sensing part 21.

[0039] The sensing part 21 and the transmitting part 22 form a cantilever beam structure 20. The cantilever beam structure 20 is rectangular. The transmitting part 22 has a high aspect ratio (the ratio of length to thickness), which can range from 200 to 800, preferably from 400 to 600. The transmitting part 22 is used to convert a small external force into a deflection change in the sensing part 21. Further, the aspect ratio of the transmitting part 22 is 500. The sensing part 21 has a thinner thickness than the transmitting part 22. For example, the ratio of the thickness of the sensing part 21 to the thickness of the transmitting part 22 in the cantilever beam structure 20 is greater than or equal to 1 / 3 and less than 1. Preferably, the thickness of the sensing part 21 is half the thickness of the transmitting part 22. A varistor 23 is designed on the first surface 211 of the sensing part 21 (which is on the same plane as the metal leads on the third surface 101 of the support structure 10) and forms a Wheatstone bridge to sense the deflection change of the transmission part 22 under external force deflection.

[0040] In this embodiment, four varistors 23 are placed at the sensing part 21 to form a Wheatstone bridge. In other embodiments, the varistors 23 may not be arranged in this way; only two varistors may be placed at the sensing part 21. In yet another embodiment, the varistors 23 may be fabricated by implantation onto a silicon substrate (sensing part 21), or other materials capable of sensing the deflection of the cantilever beam, such as graphite, may be used.

[0041] The variable stiffness cantilever beam sensor structure according to the embodiments of the present invention is a novel variable stiffness piezoresistive bionic cantilever beam sensor based on MEMS technology, which achieves ultra-sensitive sensing.

[0042] According to the variable stiffness cantilever beam sensor structure of the present invention, by using a variable stiffness structure design—different thicknesses for the transmission part and the sensing part—the local stress in the area where the piezoresistor is located is increased under the same external force, thereby improving the sensitivity of the cantilever beam sensor.

[0043] To improve the measurement threshold of the variable stiffness cantilever beam sensor structure, multiple variable stiffness cantilever beam arrays of different sizes can be designed. Since each cantilever beam has a different elastic coefficient, its response sensitivity and threshold to external forces are different. The array design can increase the detection limit of the sensor.

[0044] Therefore, to increase the detection limit and sensitivity of variable stiffness cantilever beams, this invention also provides a variable stiffness cantilever beam sensor array, including a support structure 10 and multiple cantilever beam structures 20. The support structure 10 and the multiple cantilever beam structures 20 can be integrally formed. The multiple cantilever beam structures 20 are arranged sequentially on the support structure 10. Each cantilever beam structure 20 includes a sensing part 21 and a transmission part 22 arranged sequentially in a direction away from the support structure 10. The thickness of the sensing part 21 is less than the thickness of the transmission part 22, and a piezoresistive resistor 23 is provided on the sensing part 21. Among them, at least one cantilever beam structure 20 has a transmission part 22 with a different aspect ratio than the transmission part 22 of the other cantilever beam structures 20.

[0045] In one exemplary embodiment, the aspect ratios of the transmission portions 22 of the multiple cantilever beam structures 20 are all different. Preferably, four arrays of cantilever beam structures 20 can be provided, with aspect ratios of the transmission portions 22 of the four arrays being 200, 400, 600, and 800, respectively.

[0046] The thickness of the support structure 10 is much greater than the overall thickness of the cantilever beam structure 20. The support structure 10 is mainly used to constrain one end of the cantilever beam structure 20. The support structure 10 has a third surface 101 parallel to the extension direction of the cantilever beam structure 20, and metal leads are provided on the third surface 101.

[0047] The sensing part 21 of the cantilever beam structure 20 has a first surface 211 parallel to the extending direction of the cantilever beam structure 20. A varistor 23 is disposed on the first surface 211 and electrically connected to a metal lead located on the third surface 101. The metal lead is responsible for transmitting the signal sensed by the varistor 23 on the sensing part 21. The first surface 211 of the sensing part 21 and the third surface 101 of the support structure 10 are located in the same plane. The transmitting part 22 of the cantilever beam structure 20 has a second surface 221 parallel to the extending direction of the cantilever beam structure 20. The second surface 221 is arranged parallel to the first surface 211 and the third surface 101 of the support structure 10. Preferably, the second surface 221, the first surface 211, and the third surface 101 of the support structure 10 are located in the same plane. The first surface 211 of the sensing part 21 and the second surface 221 of the transmission part 22 of the multi-set cantilever beam structure 20 are both on the same plane. This design allows for localized batch etching of the back side of the sensing part 21 (the other surface opposite to the first surface 211) using a hard mask-based technique, thereby improving the stability, consistency, uniformity, and responsiveness of the varistor 23 on the first surface 211 of the sensing part 21 to the deflection of the transmission part 22.

[0048] The sensing part 21 and the transmitting part 22 form a cantilever beam structure 20. The cantilever beam structure 20 is rectangular. The transmitting part 22 has a high aspect ratio (the ratio of length to thickness), which can range from 200 to 800, preferably from 400 to 600. The transmitting part 22 is used to convert a small external force into a deflection change in the sensing part 21. The sensing part 21 is thinner than the transmitting part 22. For example, the ratio of the thickness of the sensing part 21 to the thickness of the transmitting part 22 in the cantilever beam structure 20 is greater than or equal to 1 / 3 and less than 1. Preferably, the thickness of the sensing part 21 is 1 / 2 the thickness of the transmitting part 22. A varistor 23 is designed on the first surface 211 of the sensing part 21 (on the same plane as the metal leads on the third surface 101 of the support structure 10) and forms a Wheatstone bridge to sense the deflection change of the transmitting part 22 under external force deflection.

[0049] According to an embodiment of the present invention, a variable stiffness cantilever beam sensor array is designed with multiple cantilever beam array structures. By integrating cantilever beam structures with different aspect ratios in the transmission part, the detection limit and sensitivity of the variable stiffness cantilever beam sensor array are increased, thereby improving the performance of the sensor.

[0050] refer to Figure 2As shown, embodiments of the present invention also provide a method for fabricating the above-mentioned variable stiffness cantilever beam sensor structure, comprising: s1, providing a wafer; the wafer having a first surface and a second surface disposed opposite to each other. s2, forming a cantilever beam structure of the variable stiffness cantilever beam sensor structure on the first surface of the wafer. s3, etching the sensing portion of the cantilever beam structure from the second surface of the wafer, such that its thickness is less than the thickness of the transmitting portion. s4, disposing a piezoresistor at the sensing portion from the first surface of the wafer.

[0051] Figures 3-5 This is a schematic diagram illustrating the steps of a method for fabricating a variable stiffness cantilever beam sensor structure according to an embodiment of the present invention. The following is in conjunction with... Figures 3 to 5 The method for manufacturing the variable stiffness cantilever beam sensor structure of the present invention is described in detail.

[0052] In step s2, a cantilever beam structure of a variable stiffness cantilever beam sensor structure is formed on the first surface of the wafer, specifically including: reference Figure 3 As shown, a cantilever beam structure 20 of a variable stiffness cantilever beam sensor structure is formed and released on the first surface of wafer A. Multiple sets of cantilever beam structures 20 arranged in an array can be formed simultaneously on the first surface of wafer A by etching. The etched region B is preferably rectangular, and the cantilever beam structure 20 is located within the rectangular structure. After the cantilever beam structure 20 is released, the entire arrangement of the variable stiffness cantilever beam sensor structure on wafer A is as follows: Figure 3 As shown in the image.

[0053] In step s3, the sensing portion of the cantilever beam structure is etched from the second surface of the wafer, making its thickness less than the thickness of the transmission portion. Specifically, this includes: s301, providing a mold assembly, the mold assembly including a first mold body and a second mold body, the second mold body having a through-hole formed therein; s302, placing and positioning the wafer between the first mold body and the second mold body, wherein the first surface of the wafer is in contact with the first mold body, and the through-hole of the second mold body exposes the sensing portion of the cantilever beam structure; s303, etching the sensing portion of the cantilever beam structure through the through-hole.

[0054] refer to Figure 4As shown, after the cantilever beam structure 20 is released, the first surface of wafer A is placed against the first mold body 31. The first mold body 31 is a circular plate-shaped structure, slightly larger than the size of wafer A, with a radius approximately 1-2 cm larger than the radius of wafer A. A first limiting portion 311 for positioning wafer A is formed on the first mold body 31. A second limiting portion 312 for relative positioning against the second mold body 32 is also formed on the first mold body 31. The first limiting portion 311 can be a protruding limiting post, which can be rectangular or circular. The second limiting portion 312 can be circularly arranged limiting holes, such as drilled holes. Multiple drilled holes can be formed, with the radius of the circle containing the center of each hole equal to the radius of wafer A. The primary function of the first limiting portion 311 and the second limiting portion 312 is to determine the position of wafer A on the first mold body 31. The transverse tangent edge on wafer A (which is present on all large-size wafers) must be in contact with and tangent to the first limiting part 311. At the same time, the outer diameter of wafer A is also tangent to the outer diameter of the second limiting part 312.

[0055] The second mold body 32 is then placed on top of wafer A, as shown in the image. Figure 5 As shown. The shape of the second mold body 32 is the same as that of the wafer A, and the size and thickness of the second mold body 32 are also the same as those of the wafer A, which facilitates the determination of the position of the second mold body 32 and makes it easy to fix. A protective portion 322 with a protrusion is formed on the second mold body 32. The protective portion 322 is preferably rectangular in shape, with a length equal to the length of the etched area B on the wafer A and a width equal to the length of the transfer portion 22 of the cantilever beam structure 20. The protrusion height of the protective portion 322 is less than or equal to the thickness difference between the wafer A and the cantilever beam structure 20. Preferably, the protrusion height of the protective portion 322 is less than the thickness difference between the wafer A and the cantilever beam structure 20 by about 50-100 micrometers, so that when the second mold body 32 covers the wafer A, the protective portion 322 can just cover the cantilever beam structure 20, limiting and protecting it. The slot 321 on the second mold body 32 is formed on one side of the protective portion 322 in the length direction and is set to fit the protective portion 322. The width of the slot 321 is equal to the length of the sensing part 21 of the cantilever beam structure 20, and the length of the slot 321 is equal to the length of the protective part 322, which is also equal to the length of the etched area B on wafer A. The sum of the widths of the protective part 322 and the slot 321 is equal to the width of the etched area B on wafer A.

[0056] The second mold body 32 is placed above wafer A, and the three are fixed together by a limiting member 33. The limiting member 33 cooperates with the second limiting part 312 to relatively limit the first mold body 31 and the second mold body 32. The limiting member 33 can be a pin, and after limiting, the following is obtained: Figure 6 The structure shown.

[0057] like Figure 6 As shown, the second mold body 32 is placed above the wafer A, and the protective part 322 of the second mold body 32 is fitted to the wafer A. The second mold body 32 is aligned with the outer contour of the wafer A, and all points are tangent to each other. The three are fixed with pins, and then subsequent overall etching can be performed. At this time, only a portion of the sensing part 21 of the cantilever beam structure 20 can be etched, and variable stiffness cantilever beam sensor structures can be mass-produced.

[0058] The first mold body 31 has two main functions: firstly, to determine the placement position of wafer A; and secondly, to fix wafer A and the second mold body 32. In this embodiment, the first limiting part 311 can be a rectangular protrusion, and the limiting member 33 can be a pin. Similarly, in other embodiments, the first limiting part 311 can also be a circular protrusion, or a limiting groove formed on the surface of the first mold body 31, which is the same as the outer frame of wafer A, to determine the position of wafer A. At the same time, the limiting member 33 can also be replaced by a snap-fit ​​or other means, as long as it can achieve the limiting and locking of the first mold body 31, wafer A, and second mold body 32.

[0059] The function of the second mold body 32 is to provide large-scale protection for wafer A, while exposing certain areas for etching processes. Similarly, the material of the second mold body 32 is not limited; it can be silicon-based or glass-based. Furthermore, the size of the second mold body 32 includes, but is not limited to, the same size as wafer A; similarly, other sizes can be designed to facilitate positioning and fixing on the first mold body 31.

[0060] The method for fabricating a variable stiffness cantilever beam sensor structure according to an embodiment of the present invention utilizes MEMS process technology with hard masks to extend the process of locally etching the back side of the cantilever beam structure (the surface corresponding to the first surface of the sensing part), which can ensure the uniformity of the varistor and also enable mass production.

[0061] The method for manufacturing a variable stiffness cantilever beam sensor structure according to an embodiment of the present invention facilitates mass production and improves the yield of wafer fabrication by using specific mold components, and simplifies the process steps.

[0062] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method of fabricating a variable stiffness cantilever beam sensor structure, wherein the variable stiffness cantilever beam sensor structure comprises: A support structure and a cantilever beam structure arranged on the support structure, the cantilever beam structure comprising a sensing portion and a transferring portion arranged in sequence in a direction away from the support structure, the sensing portion having a thickness smaller than that of the transferring portion, and a piezoresistor arranged on the sensing portion, characterized in that the method for manufacturing the variable stiffness cantilever beam sensor structure comprises: providing a wafer having a first surface and a second surface arranged oppositely; forming a cantilever beam structure of the variable stiffness cantilever beam sensor structure on the first surface of the wafer; etching the sensing portion of the cantilever beam structure from the second surface of the wafer to have a thickness smaller than that of the transferring portion; and arranging a piezoresistor at the sensing portion from the first surface of the wafer; wherein the step of etching the sensing portion of the cantilever beam structure from the second surface of the wafer comprises: providing a mold assembly comprising a first mold body and a second mold body, the second mold body having a through-hole with a slot formed therein; placing the wafer between the first mold body and the second mold body and positioning, wherein the first surface of the wafer is arranged in abutment with the first mold body, and the slot of the second mold body exposes the sensing portion of the cantilever beam structure; and etching the sensing portion of the cantilever beam structure through the slot.

2. The method for manufacturing the variable stiffness cantilever beam sensor structure as described in claim 1, characterized in that, The step of providing the mold assembly comprises: providing a first mold body having a first positioning portion for positioning the wafer, and a second positioning portion for positioning the second mold body oppositely; providing a second mold body having a protruding protection portion formed thereon, the protruding height of the protection portion being smaller than or equal to the thickness difference between the wafer and the cantilever beam structure; providing a positioning member cooperating with the second positioning portion to position the first mold body and the second mold body oppositely.

3. The method for manufacturing the variable stiffness cantilever beam sensor structure as described in claim 2, characterized in that, The step of placing the wafer between the first mold body and the second mold body and positioning comprises: abutting the first surface of the wafer with the first mold body and positioning through the first positioning portion; placing the second mold body on the wafer, with the protection portion arranged corresponding to the transferring portion of the cantilever beam structure, and the slot arranged corresponding to the sensing portion of the cantilever beam structure; the positioning member cooperating with the second positioning portion to position the first mold body and the second mold body oppositely.

4. The method of claim 1, wherein the step of forming the variable stiffness cantilever beam sensor structure is performed by a process selected from the group consisting of: photolithography, electron beam lithography, and focused ion beam lithography. The sensing portion has a first surface parallel to the extension direction of the cantilever beam structure, and the piezoresistor is arranged on the first surface; The transferring portion has a second surface parallel to the extension direction of the cantilever beam structure; The first surface and the second surface are arranged in parallel.

5. The method for manufacturing the variable stiffness cantilever beam sensor structure as described in claim 4, characterized in that, The support structure has a third surface parallel to the extension direction of the cantilever beam structure, and the third surface is arranged in the same plane as the first surface; The third surface is provided with a metal lead wire connected to the piezoresistor.

6. The method of claim 1, wherein the step of forming the variable stiffness cantilever beam sensor structure is performed by a process selected from the group consisting of: photolithography, electron beam lithography, and focused ion beam lithography. The ratio of the thickness of the sensing portion to the thickness of the transferring portion is greater than or equal to 1 / 3 and less than 1.

7. The method of claim 1, wherein the step of forming the variable stiffness cantilever beam sensor structure is performed by a process selected from the group consisting of: photolithography, electron beam lithography, and focused ion beam lithography. The aspect ratio of the transferring portion is 200-800.

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