MEMS composite film stress gradient measuring device and method

Abstract

The invention discloses an MEMS composite film stress gradient measuring device and method. The measuring device comprises a V-shaped thermal actuator structure, a displacement measuring structure connected with the V-shaped thermal actuator structure and a multi-layer cantilever beam structure. The method comprises the steps that a V-shaped thermal actuator structure is used for pushing a displacement measurement structure to move towards a multi-layer cantilever beam structure, and when a contact electrode of the displacement measurement structure makes contact with a to-be-measured beam of the multi-layer cantilever beam structure, a horizontal displacement value s is obtained through reading of the displacement measurement structure; calculating the equivalent stress gradient of the composite film according to the geometric dimension of the measuring device, the horizontal displacement value s and the Young modulus of each layer of film; the MEMS composite film stress gradient measuring device and method have the advantages of being easy to operate, low in cost and high in measuring speed, and can be used for parameter monitoring of a process line.

Description

Technical Field

[0001] The present invention relates to the technical field of micro-electromechanical systems and material parameter measurement thereof, and in particular to a device and method for measuring stress gradient of a MEMS composite film. Background Art

[0002] Composite films are widely used in MEMS device structures made by surface micromachining. With the development of MEMS technology, the number of film layers is increasing, the types of film materials are increasing, and the requirements for process lines are becoming higher and higher. In order to ensure the yield of the processing line and provide MEMS designers with process parameters for designing, optimizing and predicting device performance, it is necessary to monitor the material parameters of the process line.

[0003] Stress gradient is an important parameter of composite films. In the process of processing and manufacturing composite films, the stress distribution of multilayer materials is uneven due to temperature changes, and the structure will deform after release, which will significantly change the performance of the device structure and reduce the reliability of the device. Therefore, measuring the stress gradient of the composite film is the key to predicting device performance and improving device reliability.

[0004] Among the current methods for measuring stress gradients, most have high requirements for measuring equipment and are costly. Some also require simulation to match the actual measurement results. The measurement speed is slow and is not suitable for parameter monitoring of process lines. Summary of the invention

[0005] The purpose of the present invention is to provide a MEMS composite film stress gradient measurement device and method, which has low measurement cost and fast measurement speed and can be used for parameter monitoring of process lines. To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a MEMS composite film stress gradient measurement device, comprising: a V-shaped thermal actuator structure, a displacement measurement structure connected to the V-shaped thermal actuator structure, and a multilayer cantilever beam structure;

[0007] The V-shaped thermal actuator structure comprises: a connecting beam, a plurality of pairs of V-shaped thermal arms arranged on the connecting beam, a first anchoring area, a second anchoring area, a first metal electrode and a second metal electrode; the V-shaped thermal actuator structure is symmetrically arranged about the connecting beam; the first anchoring area and the second anchoring area are respectively connected to two ends of the plurality of pairs of V-shaped thermal arms; the first metal electrode and the second metal electrode are respectively placed in the first anchoring area and the second anchoring area;

[0008] The displacement measurement structure comprises: a moving tooth, a contact electrode, and a first fixed tooth and a second fixed tooth respectively arranged on both sides of the moving tooth; the contact electrode is arranged at one end of the moving tooth;

[0009] The multi-layer cantilever beam structure comprises: a beam to be measured, a third anchoring area connected to the beam to be measured, and a third metal electrode; the third metal electrode is placed in the third anchoring area;

[0010] The connecting beam of the V-shaped thermal actuator structure is connected to the end of the moving tooth away from the contact electrode; there is a gap between the contact electrode of the displacement measurement structure and the beam to be measured of the multi-layer cantilever beam structure; the beam to be measured, the moving tooth, the contact electrode and the connecting beam are all on the same horizontal axis.

[0011] Optionally, before the sacrificial layer is released, the horizontal initial spacing between the displacement measurement structure and the multi-layer cantilever beam structure is d; wherein the sacrificial layer is disposed between the measurement device and the substrate when the measurement device is manufactured.

[0012] Optionally, the movable tooth includes a main beam, and a first comb tooth assembly and a second comb tooth assembly symmetrically connected on both sides of the main beam; one end of the main beam is connected to the connecting beam, and the other end is connected to the contact electrode; the first comb tooth assembly and the second comb tooth assembly each include m teeth, the width of the teeth is a, and the tooth spacing is b.

[0013] Optionally, the first fixed teeth include a first base beam and a comb tooth assembly A; the comb tooth assembly A corresponds to the first comb tooth assembly, and includes m fixed teeth A evenly distributed on the first base beam; the second fixed teeth include a second base beam and a comb tooth assembly B; the comb tooth assembly B corresponds to the second comb tooth assembly, and includes m fixed teeth B evenly distributed on the second base beam.

[0014] Optionally, the width of the fixed teeth A and the fixed teeth B are both a, and the tooth spacing is both b+Δ.

[0015] Optionally, in the initial state of the measuring device, the comb tooth assembly A is offset to the right by Δ compared to the first comb tooth assembly of the moving teeth, and the comb tooth assembly B is offset to the right by (m+1)Δ compared to the second comb tooth assembly of the moving teeth; wherein the right direction is the direction of the multi-layer cantilever beam structure.

[0016] Optionally, the beam to be tested is composed of a composite film; the length of the composite film is L, and the width is w; the composite film includes n layers of films, and the thicknesses of the n layers of films are h1, h2, ..., h n .

[0017] Optionally, the material of the connecting beam, the multiple pairs of V-shaped thermal arms, and the displacement measurement structure is the same as the material of the first layer of the thin film of the beam to be measured, which is polycrystalline silicon.

[0018] Optionally, the thickness of the contact electrode is h1.

[0019] In a second aspect, the present invention provides a method for measuring stress gradient of a MEMS composite film using the measuring device of the first aspect, comprising:

[0020] The first metal electrode is grounded, and the second metal electrode is connected to a high potential, and the V-shaped thermal actuator structure is electrically heated, so that the V-shaped thermal actuator structure pushes the displacement measurement structure to move in the direction of the multi-layer cantilever beam structure;

[0021] The resistance between the first metal electrode and the third metal electrode is monitored in real time. When the contact electrode of the displacement measurement structure contacts the beam to be measured of the multi-layer cantilever beam structure, the monitored resistance suddenly changes from infinity to a finite value, and the horizontal displacement value s displayed by the displacement measurement structure at this time is read; the horizontal displacement value s is the moving distance of the movable tooth compared to the initial state;

[0022] Based on the geometric dimensions of the measuring device, the Young's modulus of each layer of the film, and the horizontal displacement value s, the equivalent stress gradient of the composite film is calculated as follows:

[0023]

[0024]

[0025] in, It represents the equivalent stress gradient of the composite film; They represent the thickness of the i-th film, j-th film and k-th film in the composite film respectively; , represent the Young's modulus of the i-th film and the k-th film respectively; L represents the length of the beam to be measured, that is, the length of the composite film; d represents the horizontal initial spacing between the displacement measurement structure and the multilayer cantilever beam structure.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention provides a MEMS composite film stress gradient measuring device, comprising: a V-shaped thermal actuator structure, a displacement measuring structure connected to the V-shaped thermal actuator structure, and a multi-layer cantilever beam structure; the V-shaped thermal actuator structure is used to push the displacement measuring structure to move in the direction of the multi-layer cantilever beam structure, and when a contact electrode of the displacement measuring structure contacts a beam to be measured of the multi-layer cantilever beam structure, a horizontal displacement of the V-shaped thermal actuator structure, that is, a horizontal displacement value s, is obtained through a reading of the displacement measuring structure; the equivalent stress gradient of the composite film is calculated based on the geometric dimensions of the measuring device, the horizontal displacement value s, and the Young's modulus of each layer of the film; the MEMS composite film stress gradient measuring device and method designed by the present invention have the advantages of simple operation, low cost, and high measurement speed, and can be used for parameter monitoring of a process line. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The figure is a schematic structural diagram of a MEMS composite film stress gradient measuring device in one embodiment of the present invention;

[0029] Figure 2 Shown is a flow chart of a method for measuring stress gradient of a MEMS composite film in one embodiment of the present invention;

[0030] In the figure: 201-208, hot arm; 209, connecting beam; 210, first anchor area; 211, first metal electrode; 212, second anchor area; 213, second metal electrode; 301, moving tooth; 302, first fixed tooth; 303, second fixed tooth; 304, contact electrode; 101, beam to be measured; 102, third anchor area; 103, third metal electrode. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may also include different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0033] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0034] Example 1

[0035] The embodiment of the present invention introduces a MEMS composite film stress gradient measurement device, such as Figure 1 As shown, it includes: a V-shaped thermal actuator structure, a displacement measurement structure connected to the V-shaped thermal actuator structure, and a multi-layer cantilever beam structure;

[0036] The V-shaped thermal actuator structure comprises: a connecting beam 209, a plurality of pairs of V-shaped thermal arms arranged on the connecting beam 209, a first anchoring area 210, a second anchoring area 212, a first metal electrode 211 and a second metal electrode 213; the V-shaped thermal actuator structure is symmetrically arranged with respect to the connecting beam 209; the first anchoring area 210 and the second anchoring area 212 are respectively connected to two ends of the plurality of pairs of V-shaped thermal arms; the first metal electrode 211 and the second metal electrode 213 are respectively placed in the first anchoring area 210 and the second anchoring area 212;

[0037] The displacement measurement structure includes: a moving tooth 301, a contact electrode 304, and a first fixed tooth 302 and a second fixed tooth 303 respectively arranged on both sides of the moving tooth 301; the contact electrode 304 is arranged at one end of the moving tooth 301;

[0038] The multi-layer cantilever beam structure comprises: a beam to be measured 101, a third anchor region 102 connected to the beam to be measured 101, and a third metal electrode 103; the third metal electrode 103 is disposed in the third anchor region 102;

[0039] The connecting beam 209 of the V-shaped thermal actuator structure is connected to the end of the moving tooth 301 away from the contact electrode 304; there is a gap between the contact electrode 304 of the displacement measurement structure and the beam to be measured 101 of the multi-layer cantilever beam structure; the beam to be measured 101, the moving tooth 301, the contact electrode 304 and the connecting beam 209 are all on the same horizontal axis.

[0040] Specifically, in this embodiment, the multiple pairs of V-shaped hot arms include 4 pairs of V-shaped hot arms 201-202, 203-204, 205-206 and 207-208; the entire V-shaped thermal actuator structure is a symmetrical structure with the connecting beam 209 as the axis, and the ends of the hot arms 201, 203, 205 and 207 away from the connecting beam 209 are all connected to the first anchor area 210, and the ends of the hot arms 202, 204, 206 and 208 away from the connecting beam 209 are all connected to the second anchor area 212.

[0041] In this embodiment, there is no connection relationship between the displacement measurement structure and the multi-layer cantilever beam structure. Before the sacrificial layer is released, the horizontal initial spacing between the displacement measurement structure and the multi-layer cantilever beam structure is precisely set to a distance d, that is, the size of the gap between the contact electrode 304 and the beam to be measured 101 is d; this spacing d is one of the key factors to ensure that the displacement measurement can be carried out accurately; wherein, the sacrificial layer is arranged between the measuring device and the substrate when the measuring device is manufactured.

[0042] In this embodiment, the movable tooth 301 includes a main beam, and a first comb tooth assembly and a second comb tooth assembly symmetrically connected on both sides of the main beam; one end of the main beam is connected to the connecting beam 209, and the other end is connected to the contact electrode 304; the first comb tooth assembly and the second comb tooth assembly each include m teeth, the width of the teeth is a, and the tooth spacing is b; specifically, Figure 1 There are 9 teeth distributed on the upper and lower sides of the middle moving tooth 301, if m=9 as shown in the figure;

[0043] In this embodiment, the first fixed teeth 302 include a first base beam and a comb tooth assembly A; the comb tooth assembly A corresponds to the first comb tooth assembly, and the comb tooth assembly A and the first comb tooth assembly are on the same side of the first base beam; the comb tooth assembly A includes m fixed teeth A evenly distributed on the first base beam; the second fixed teeth 303 include a second base beam and a comb tooth assembly B; the comb tooth assembly B corresponds to the second comb tooth assembly, and the comb tooth assembly B and the second comb tooth assembly are on the same side of the second base beam; the comb tooth assembly B includes m fixed teeth B evenly distributed on the second base beam;

[0044] Specifically, anchor regions are provided on the first fixed tooth 302 and the second fixed tooth 303 for fixing the first fixed tooth 302 and the second fixed tooth 303 on the substrate.

[0045] Specifically, in Figure 1 The first fixed teeth 302 are located above the moving teeth 301, and the second fixed teeth 303 are located below the moving teeth 301, and 9 fixed teeth A and 9 fixed teeth B are respectively provided on the first fixed teeth 302 and the second fixed teeth 303;

[0046] Specifically, the width of the fixed teeth A and the fixed teeth B are both a, and the tooth spacing is b+Δ, which refers to the spacing distance between the fixed teeth A and the spacing distance between the fixed teeth B.

[0047] Specifically, in the initial state of the measuring device, the comb tooth assembly A is offset to the right by Δ compared to the first comb tooth assembly of the movable tooth 301, and the comb tooth assembly B is offset to the right by (m+1)Δ compared to the second comb tooth assembly of the movable tooth 301; wherein the right direction is the direction of the multi-layer cantilever beam structure.

[0048] In this embodiment, the beam 101 to be tested is composed of a composite film; the length of the composite film is L, and the width is w; the composite film includes n layers of film, and the thicknesses of the n layers of film are h1, h2, ..., h n .

[0049] Specifically, the materials of the connecting beam 209, the hot arms 201-208, the moving and fixed teeth 301-303, and the contact electrode 304 are the same as those of the beam 101 to be tested, that is, the first layer of the composite film, which are all polysilicon. The thickness of the contact electrode 304 is h1.

[0050] Example 2

[0051] Based on the measuring device described in Example 1, the embodiment of the present invention introduces a method for measuring stress gradient of a MEMS composite film, including:

[0052] Step S1, grounding the first metal electrode and connecting the second metal electrode to a high potential, electrically heating the V-shaped thermal actuator structure, so that the V-shaped thermal actuator structure pushes the displacement measurement structure to move in the direction of the multi-layer cantilever beam structure;

[0053] Step S2, monitoring the resistance between the first metal electrode and the third metal electrode in real time, when the contact electrode of the displacement measurement structure contacts the beam to be measured of the multilayer cantilever beam structure, the monitored resistance suddenly changes from infinity to a finite value, and reading the horizontal displacement value s displayed by the displacement measurement structure at this time;

[0054] Specifically, the horizontal displacement value s is the moving distance of the movable tooth compared to the initial state;

[0055] Step S3, calculating the equivalent stress gradient of the composite film based on the geometric dimensions of the measuring device, the Young's modulus of each layer of the film, and the horizontal displacement value s.

[0056] Specifically, step S3 needs to be calculated by the following formula:

[0057]

[0058]

[0059] in, It represents the equivalent stress gradient of the composite film; They represent the thickness of the i-th film, j-th film and k-th film in the composite film respectively; , represent the Young's modulus of the i-th film and the k-th film respectively; L represents the length of the beam to be measured, that is, the length of the composite film; d represents the horizontal initial spacing between the displacement measurement structure and the multilayer cantilever beam structure.

[0060] Specifically, for ease of understanding, the theoretical principle of the measurement method proposed in the present invention is explained:

[0061] For an n-layer cantilever beam structure with equal width, the distance z between the neutral plane of the beam 101 to be measured and the lower surface of the beam is c It can be expressed as:

[0062]

[0063] The moment of inertia of the area on the cross section of the i-th film layer about the neutral axis can be calculated using the following formula:

[0064]

[0065] Among them, A i is the cross-sectional area of ​​the i-th film, and z represents the distance between a point on the film cross section and the lower surface of the beam. Therefore, the bending stiffness of an n-layer cantilever beam of equal width can be expressed as:

[0066]

[0067] in, .

[0068] Under the action of stress gradient, the n-layer cantilever beam with equal width, i.e., the beam to be tested 101, bends and presents an arc shape. The arc length is the beam length L of the beam to be tested 101. At this time, the internal bending moment M of the beam is proportional to the stress gradient. The following relationship exists:

[0069]

[0070] Assuming the radius of curvature of the arc is r, then

[0071]

[0072] Substituting formula (3) and formula (4) into formula (5), we can obtain:

[0073]

[0074] Based on the above principle, this embodiment provides a method for measuring stress gradient of a MEMS composite film. The specific measurement process is as follows:

[0075] First, the first metal electrode 211 is grounded, and the second metal electrode 213 is connected to a high potential, and the V-shaped thermal actuator is electrically heated. At this time, the V-shaped thermal actuator structure pushes the movable tooth 301 and the contact electrode 304 to move toward the cantilever beam.

[0076] At the same time, the resistance between the first metal electrode 211 and the third metal electrode 103 is monitored. When the contact electrode 304 contacts the beam 101 to be measured, the monitored resistance changes from infinity to a finite value, and the horizontal displacement value s displayed by the vernier scale (displacement measurement structure) is read. For example, if the first tooth from left to right of the first comb tooth assembly in the movable tooth 301 is aligned with the first fixed tooth A from left to right of the comb tooth assembly A in the first fixed tooth 302, then s=Δ, if the second tooth from left to right of the first comb tooth assembly in the movable tooth 301 is aligned with the second fixed tooth A from left to right of the comb tooth assembly A in the first fixed tooth 302, then s=2Δ, and so on, if the mth tooth from left to right of the first comb tooth assembly in the movable tooth 301 is aligned with the mth fixed tooth A from left to right of the comb tooth assembly A in the first fixed tooth 302, then s=mΔ; similarly, if the first tooth from left to right of the second comb tooth assembly is aligned with the first fixed tooth B from left to right of the comb tooth assembly B in the second fixed tooth 303, then s=(m+1)Δ, if the second tooth from left to right of the second comb tooth assembly is aligned with the second fixed tooth B from left to right of the comb tooth assembly B in the second fixed tooth 303, then s=(m+2)Δ , and so on, if at this time the mth tooth from left to right of the second comb tooth assembly is aligned with the mth fixed tooth B from left to right of the comb tooth assembly B in the second fixed tooth 303, then s=2mΔ.

[0077] Assuming that the arc length of the contact point where the beam 101 to be tested contacts the contact electrode 304 is L1, according to the geometric relationship of the cantilever beam structure after bending, it can be obtained that:

[0078]

[0079] Solving formula (7) and formula (8), we can get the radius of curvature r:

[0080]

[0081] Substituting formula (9) into formula (6) yields:

[0082]

[0083] Therefore, based on the geometric dimensions of the measuring device, the Young's modulus of the composite film, and the measured horizontal displacement value s, the equivalent stress gradient of the composite film is calculated by formula (10).

[0084] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. A MEMS composite film stress gradient measurement device, characterized in that: include: A V-shaped thermal actuator structure, a displacement measuring structure connected to the V-shaped thermal actuator structure, and a multi-layer cantilever beam structure; The V-shaped thermal actuator structure comprises: a connecting beam, a plurality of pairs of V-shaped thermal arms arranged on the connecting beam, a first anchoring area, a second anchoring area, a first metal electrode and a second metal electrode; the V-shaped thermal actuator structure is symmetrically arranged about the connecting beam; the first anchoring area and the second anchoring area are respectively connected to two ends of the plurality of pairs of V-shaped thermal arms; the first metal electrode and the second metal electrode are respectively placed in the first anchoring area and the second anchoring area; The displacement measurement structure comprises: a moving tooth, a contact electrode, and a first fixed tooth and a second fixed tooth respectively arranged on both sides of the moving tooth; the contact electrode is arranged at one end of the moving tooth; The multi-layer cantilever beam structure comprises: a beam to be measured, a third anchoring area connected to the beam to be measured, and a third metal electrode; the third metal electrode is placed in the third anchoring area; The connecting beam of the V-shaped thermal actuator structure is connected to the end of the moving tooth away from the contact electrode; there is a gap between the contact electrode of the displacement measurement structure and the beam to be measured of the multi-layer cantilever beam structure; the beam to be measured, the moving tooth, the contact electrode and the connecting beam are all on the same horizontal axis.

2. The MEMS composite film stress gradient measuring device according to claim 1, characterized in that: Before the sacrificial layer is released, the horizontal initial distance between the displacement measurement structure and the multi-layer cantilever beam structure is d; wherein the sacrificial layer is arranged between the measurement device and the substrate when the measurement device is manufactured.

3. The MEMS composite film stress gradient measuring device according to claim 2, characterized in that: The movable teeth include a main beam, and a first comb tooth assembly and a second comb tooth assembly symmetrically connected on both sides of the main beam; one end of the main beam is connected to the connecting beam, and the other end is connected to the contact electrode; the first comb tooth assembly and the second comb tooth assembly each include m teeth, the width of the teeth is a, and the tooth spacing is b.

4. The MEMS composite film stress gradient measuring device according to claim 3, characterized in that: The first fixed teeth include a first base beam and a comb tooth assembly A; the comb tooth assembly A corresponds to the first comb tooth assembly, and includes m fixed teeth A evenly distributed on the first base beam; the second fixed teeth include a second base beam and a comb tooth assembly B; the comb tooth assembly B corresponds to the second comb tooth assembly, and includes m fixed teeth B evenly distributed on the second base beam.

5. The MEMS composite film stress gradient measuring device according to claim 4, characterized in that: The widths of the fixed teeth A and B are both a, and the tooth spacings are both b+D.

6. The MEMS composite film stress gradient measuring device according to claim 5, characterized in that: In the initial state of the measuring device, the comb tooth assembly A is offset to the right by D compared to the first comb tooth assembly of the moving teeth, and the comb tooth assembly B is offset to the right by (m+1)D compared to the second comb tooth assembly of the moving teeth; wherein the right direction is the direction of the multi-layer cantilever beam structure.

7. The MEMS composite film stress gradient measuring device according to claim 6, characterized in that: The beam to be tested is composed of a composite film; the length of the composite film is L, and the width is w; the composite film includes n layers of film, and the thicknesses of the n layers of film are respectively h 1, h 2,……, h n .

8. The MEMS composite film stress gradient measuring device according to claim 7, characterized in that: The materials of the connecting beam, the multiple pairs of V-shaped thermal arms, and the displacement measurement structure are the same as the material of the first layer of the thin film of the beam to be measured, which are all polycrystalline silicon.

9. The MEMS composite film stress gradient measuring device according to claim 8, characterized in that: The thickness of the contact electrode is h 1.

10. A method for measuring stress gradient of a MEMS composite film using the measuring device of claim 9, characterized in that: include: The first metal electrode is grounded, and the second metal electrode is connected to a high potential, and the V-shaped thermal actuator structure is electrically heated, so that the V-shaped thermal actuator structure pushes the displacement measurement structure to move in the direction of the multi-layer cantilever beam structure; The resistance between the first metal electrode and the third metal electrode is monitored in real time. When the contact electrode of the displacement measurement structure contacts the beam to be measured of the multi-layer cantilever beam structure, the monitored resistance suddenly changes from infinity to a finite value, and the horizontal displacement value s displayed by the displacement measurement structure at this time is read; the horizontal displacement value s is the moving distance of the movable tooth compared to the initial state; Based on the geometric dimensions of the measuring device, the Young's modulus of each layer of the film, and the horizontal displacement value s, the equivalent stress gradient of the composite film is calculated, and the formula is as follows: ； ； in, It represents the equivalent stress gradient of the composite film; Respectively represent the i Thin film, j The film and k The thickness of the film; , respectively representing the i The film and k Young's modulus of the thin film; L represents the length of the beam to be measured, that is, the length of the composite film; d represents the horizontal initial spacing between the displacement measurement structure and the multilayer cantilever beam structure.

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