A MEMS structure

Abstract

The present application discloses a MEMS structure, comprising: a substrate, comprising an outer ring body and a first inner ring body arranged inside the outer ring body and spaced apart from the outer ring body, wherein there are cavities between the outer ring body and the first inner ring body and inside the first inner ring body; a piezoelectric composite vibration layer, formed above the substrate, wherein the piezoelectric composite vibration layer comprises a fixed end connected to the first inner ring body and a free end suspended above the cavity. The present application shortens the length of the cantilever beam from the fixed end to the free end by providing one or more inner ring bodies, thereby reducing the probability of diaphragm warping of the piezoelectric composite vibration layer. The multiple cantilever beam structures in the piezoelectric composite vibration layer effectively improve the sensitivity.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to a MEMS (abbreviation for MicroelectroMechanical Systems) structure. Background Art

[0002] MEMS microphones mainly include capacitive and piezoelectric types. MEMS piezoelectric microphones are microphones made using micro-electromechanical system technology and piezoelectric film technology. Due to the use of semiconductor planar technology and bulk silicon processing technology, they are small in size, small in volume, and have good consistency. At the same time, compared with capacitive microphones, they also have the advantages of not requiring bias voltage, a wide operating temperature range, and being dustproof and waterproof. However, their sensitivity is relatively low, which restricts the development of MEMS piezoelectric microphones. Moreover, when the diaphragm size of the MEMS piezoelectric microphone is large, it is easy to cause the diaphragm to warp.

[0003] With regard to how to improve the problems of low sensitivity of piezoelectric MEMS structures and easy warping of diaphragms in related technologies, no effective solution has been proposed so far. Summary of the invention

[0004] In response to the problems in the related art, the present application proposes a MEMS structure that can reduce the probability of diaphragm warping and improve sensitivity.

[0005] The technical solution of this application is implemented as follows:

[0006] According to one aspect of the present application, a MEMS structure is provided, comprising:

[0007] The substrate comprises an outer ring body and a first inner ring body disposed in the outer ring body and spaced apart from the outer ring body, wherein a cavity is provided between the outer ring body and the first inner ring body and inside the first inner ring body;

[0008] A piezoelectric composite vibration layer is formed above the substrate, and the piezoelectric composite vibration layer includes a fixed end connected to the first inner ring body and a free end suspended above the cavity.

[0009] Among them, the piezoelectric composite vibration layer includes one or more first diaphragms arranged at intervals along the circumference of the first inner ring body, the fixed end of the first diaphragm is connected to the first inner ring body, and the free end of the first diaphragm extends toward the center of the piezoelectric composite vibration layer.

[0010] Among them, the piezoelectric composite vibration layer includes one or more second diaphragms arranged at intervals along the circumference of the first inner ring body, the fixed end of the second diaphragm is connected to the first inner ring body, and the free end of the second diaphragm extends in a direction away from the center of the piezoelectric composite vibration layer.

[0011] Wherein, the projection contour of the free end of the second diaphragm in the vibration direction is located inside the second inner ring body.

[0012] Wherein, the substrate also includes one or more first support plates, the first end of the first support plate is connected to the outer ring body, the second end of the first support plate is connected to the first inner ring body, and the first support plate, the outer ring body, and the first inner ring body form a plurality of the cavities.

[0013] Wherein, the substrate further includes a second inner ring body, and the second inner ring body is located between the outer ring body and the first inner ring body.

[0014] The middle end of the first support plate is connected to the second inner ring body, and the first support plate, the outer ring body, the first inner ring body, and the second inner ring body form a plurality of cavities.

[0015] Among them, the piezoelectric composite vibration layer includes one or more third diaphragms arranged at intervals along the circumference of the second inner ring body, the fixed end of the third diaphragm is connected to the second inner ring body, and the free end of the third diaphragm extends in a direction away from the center of the piezoelectric composite vibration layer.

[0016] Wherein, the projection contour of the free end of the third diaphragm in the vibration direction is located inside the outer ring body.

[0017] The piezoelectric composite vibration layer has a plurality of gaps, the positions of the gaps correspond to the positions of the first supports, and the widths of the gaps are greater than the thickness of the first support plate.

[0018] In the MEMS structure, one or more inner ring bodies are arranged in the outer ring body of the substrate, and the one or more inner ring bodies are used as the fixed ends of the cantilever beams of the diaphragm of the piezoelectric composite vibration layer. Therefore, compared with the technical solution that does not contain an inner ring body in the MEMS structure, the present application shortens the length of the cantilever beam from the fixed end to the free end by setting one or more inner ring bodies, thereby reducing the probability of warping of the diaphragm of the piezoelectric composite vibration layer. Moreover, since the probability of warping of the diaphragm of the piezoelectric composite vibration layer is reduced, the process difficulty of the MEMS structure is reduced, and the yield and stability of the device are improved. In addition, the fixed end and the free end are freely designed in the MEMS structure in the present application, so that the sensitivity of the multiple cantilever beam structures in the piezoelectric composite vibration layer is effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 shows an exploded view of a MEMS structure provided according to some embodiments;

[0021] Figure 2 shows a cross-sectional perspective view of a MEMS structure provided according to some embodiments;

[0022] Figure 3 shows a perspective view of a MEMS structure provided according to some embodiments;

[0023] Figure 4 shows a cross-sectional perspective view of a MEMS structure provided according to some embodiments;

[0024] Figures 5 to 9 Shown according to Figure 2 Cross-sectional views of intermediate stages in the formation of a MEMS structure are provided. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the present application belong to the scope of protection of this application.

[0026] See also Figure 1 and Figure 2 According to an embodiment of the present application, a MEMS structure is provided, which can be used for, but not limited to, sensors such as microphones or other actuators. In some embodiments, the MEMS structure includes a substrate 10 and a piezoelectric composite vibration layer 20.

[0027] The substrate 10 includes an outer ring body 11 and a first inner ring body 12 disposed inside the outer ring body 11 and spaced apart from the outer ring body 11. A cavity 14 is provided between the outer ring body 11 and the first inner ring body 12 and inside the first inner ring body 12.

[0028] The piezoelectric composite vibration layer 20 is formed above the substrate 10 , and the piezoelectric composite vibration layer 20 includes a fixed end connected to the first inner ring body 12 and a free end suspended above the cavity 14 .

[0029] In the MEMS structure, since the substrate 10 includes an outer ring body 11 and a first inner ring body 12, and the piezoelectric composite vibration layer 20 is fixedly connected to the first inner ring body 12 to form a cantilever beam. Therefore, the present application provides a new MEMS structure and simplifies the process steps. The MEMS structure and its manufacturing method will be described in detail below.

[0030] See also Figure 5 Step S101, forming a piezoelectric composite vibration layer 20 on the front surface of the substrate 10. The material of the substrate 10 includes silicon or any suitable silicon-based compound or derivative (such as silicon wafer, SOI, SiO2). The method of forming the piezoelectric composite vibration layer 20 includes:

[0031] A support material is deposited on the substrate 10 to form a vibration support layer 21. The vibration support layer 21 includes a single layer or multilayer composite film structure composed of silicon nitride (Si3N4), silicon oxide, single crystal silicon, polycrystalline silicon, or other suitable support materials. Considering the problem of controlling the stress of the vibration support layer 21, the vibration support layer 21 can be set to a multilayer structure to reduce the stress. The method of forming the vibration support layer 21 includes a thermal oxidation method or a chemical vapor deposition method. In some embodiments, the step of forming the vibration support layer 21 can be skipped or omitted.

[0032] A first electrode material is deposited on the vibration support layer 21 , and the first electrode material is patterned to form a first electrode layer 22 .

[0033] A piezoelectric material is deposited on the first electrode layer 22, and the piezoelectric material is patterned to form a first piezoelectric layer 23. In some embodiments, the material of the first piezoelectric layer 23 includes one or more layers of zinc oxide, aluminum nitride, an organic piezoelectric film, lead zirconate titanate, a perovskite piezoelectric film, or other suitable materials. The method of forming the first piezoelectric layer 23 includes magnetron sputtering, deposition, or other suitable methods.

[0034] A second electrode material is deposited on the first piezoelectric layer 23, and the second electrode material is patterned to form a second electrode layer 24. The materials of the first electrode layer 22 and the second electrode layer 24 include aluminum, gold, platinum, molybdenum, titanium, chromium, and composite films thereof or other suitable materials. The method of forming the first electrode layer 22 and the second electrode layer 24 includes physical vapor deposition or other suitable methods.

[0035] In this embodiment, the first electrode layer 22, the first piezoelectric layer 23 and the second electrode layer 24 constitute a piezoelectric composite layer. The first piezoelectric layer 23 can convert the applied pressure into voltage, and the first electrode layer 22 and the second electrode layer 24 can transmit the generated voltage to other integrated circuit devices. The first electrode layer 22 and the second electrode layer 24 have at least two mutually isolated partitions, and the mutually corresponding partitions of the first electrode layer 22 and the second electrode layer 24 constitute electrode layer pairs, and multiple electrode layer pairs are sequentially connected in series.

[0036] In some embodiments, a second piezoelectric layer (not shown in the figure) is formed above the second electrode layer 24, and a third electrode layer (not shown in the figure) is formed above the second piezoelectric layer. The material of the second piezoelectric layer includes one or more layers of zinc oxide, aluminum nitride, organic piezoelectric film, lead zirconate titanate, perovskite piezoelectric film, or other suitable materials. The material and formation method of the second piezoelectric layer may be the same as or different from the material and formation method of the first piezoelectric layer 23. The material of the third electrode layer includes aluminum, gold, platinum, molybdenum, titanium, chromium, and composite films composed thereof or other suitable materials. The material and formation method of the third electrode layer may be the same as or different from the material and formation method of the first electrode layer 22. Moreover, in this embodiment, the piezoelectric composite layer of the MEMS structure has the first electrode layer 22, the first piezoelectric layer 23, the second electrode layer 24, the second piezoelectric layer and the third electrode layer, thereby forming a dual-chip structure, which improves the piezoelectric conversion efficiency of the MEMS structure. In addition, in an embodiment where the vibration support layer 21 is not provided, the second piezoelectric layer and the third electrode layer may be formed in sequence above the second electrode layer 24. In the embodiment with the vibration support layer 21, there is no second piezoelectric layer and third electrode layer above the second electrode layer 24. Figure 5 In the illustrated embodiment, the piezoelectric composite vibration layer 20 includes a vibration support layer 21 , a first electrode layer 22 , a first piezoelectric layer 23 and a second electrode layer 24 .

[0037] See also Figure 6 , step S102, etching the back side of the substrate 10 until reaching the piezoelectric composite vibration layer 20, wherein the substrate 10 includes an outer ring body 11 and a first inner ring body 12 disposed inside the outer ring body 11 and spaced apart from the outer ring body 11, and a cavity 14 is provided between the outer ring body 11 and the first inner ring body 12 and inside the first inner ring body 12. The cavity 14 can be formed by DRIE (abbreviation for Deep Reactive Ion Etching) or wet etching.

[0038] Please refer to the comprehensive Figure 1 , Figure 2 and Figure 6In some embodiments, the substrate 10 may include an outer ring body 11 and a first inner ring body 12. In addition, the substrate 10 also includes one or more first support plates 15 for supporting and connecting the outer ring body 11 and the first inner ring body 12. The first end of the first support plate 15 is connected to the outer ring body 11, and the second end of the first support plate 15 is connected to the first inner ring body 12. The first support plate 15, the outer ring body 11, and the first inner ring body 12 form a plurality of cavities 14. Figure 1 In the illustrated embodiment, a portion of the first support plate 15 is disposed within the first inner ring body 12. In other embodiments, a portion of the first support plate 15 may not be disposed within the first inner ring body 12.

[0039] In some embodiments, the substrate 10 may include an outer ring body 11, a first inner ring body 12, and a second inner ring body 13. The second inner ring body 13 is located between the outer ring body 11 and the first inner ring body 12. In this embodiment, the middle end of the first support plate 15 is connected to the second inner ring body 13. The first support plate 15, the outer ring body 11, the first inner ring body 12, and the second inner ring body 13 form a plurality of cavities 14.

[0040] In some embodiments, the shape of the outer ring body 11 is similar to that of the first inner ring body 12 and the second inner ring body 13 , and is circular, square, or other polygonal shapes. Figure 3 and Figure 4 A square MEMS structure is shown, and in this case the outer ring body 11 is square.

[0041] See also Figure 7 , step S103, conformally forming a sacrificial support layer 30 on the back side of the substrate 10. In subsequent steps, the sacrificial support layer 30 is used to support the piezoelectric composite vibration layer 20. The material of the sacrificial support layer 30 includes aluminum material, LTO (short for Low Temperature Oxide, i.e., low temperature oxide) or other easily corrosive materials. The method of forming the sacrificial support layer 30 includes physical vapor deposition, chemical vapor deposition or other suitable methods.

[0042] See also Figure 8 In step S104 , the piezoelectric composite vibration layer 20 is etched and split so that the piezoelectric composite vibration layer 20 includes a fixed end connected to the first inner ring body 12 and a free end suspended above the cavity 14 .

[0043] Please refer to the comprehensive Figure 8 and Figure 2In the embodiment where the substrate 10 includes an outer ring body 11 and a first inner ring body 12, the piezoelectric composite vibration layer 20 includes one or more first diaphragms 20a arranged at intervals along the circumference of the first inner ring body 12, the fixed end of the first diaphragm 20a is connected to the first inner ring body 12, and the free end of the first diaphragm 20a extends toward the center of the piezoelectric composite vibration layer 20. Alternatively, the piezoelectric composite vibration layer 20 includes one or more second diaphragms 20b arranged at intervals along the circumference of the first inner ring body 12, the fixed end of the second diaphragm 20b is connected to the first inner ring body 12, and the free end of the second diaphragm 20b extends in a direction away from the center of the piezoelectric composite vibration layer 20. The projection contour of the free end of the second diaphragm 20b in the vibration direction is located inside the second inner ring body 13. In some embodiments, the piezoelectric composite vibration layer 20 may include only the first diaphragm 20a, or only the second diaphragm 20b. In some embodiments, the piezoelectric composite vibration layer 20 may have a first diaphragm 20a and a second diaphragm 20b.

[0044] In the embodiment where the substrate 10 includes an outer ring body 11, a first inner ring body 12, and a second inner ring body 13, the piezoelectric composite vibration layer 20 further includes one or more third diaphragms 20c arranged at intervals along the circumference of the second inner ring body 13, the fixed end of the third diaphragm 20c is connected to the second inner ring body 13, and the free end of the third diaphragm 20c extends in a direction away from the center of the piezoelectric composite vibration layer 20. The projection contour of the free end of the third diaphragm 20c in the vibration direction is located on the inner side of the outer ring body 11.

[0045] In other embodiments, the substrate 10 may include two or more inner ring bodies and an outer ring body 11, and the fixed end of the piezoelectric composite vibration layer 20 is connected to the inner ring body, thereby dividing the piezoelectric composite vibration layer 20 into multiple diaphragms in the radial direction.

[0046] See also Fig. 9 , step S105, after the piezoelectric composite vibration layer 20 is segmented, the sacrificial support layer 30 is removed. After the sacrificial support layer 30 is removed, the free ends of the first diaphragm 20a, the second diaphragm 20b, and the third diaphragm 20c of the piezoelectric composite vibration layer 20 are freed from constraints, thereby forming a piezoelectric composite vibration layer 20 of a cantilever beam structure. And after the sacrificial support layer 30 is removed, the piezoelectric composite vibration layer 20 has a plurality of gaps 20d, the positions of the gaps 20d correspond to the positions of the first support plate 15, and the widths of the gaps 20d are greater than the thickness of the first support plate 15.

[0047] In the MEMS structure formed based on the above manufacturing method, one or more inner ring bodies are arranged inside the outer ring body 11 of the substrate 10, and the one or more inner ring bodies are used as the fixed ends of the cantilever beams of the diaphragm of the piezoelectric composite vibration layer 20. Therefore, compared with the technical solution that does not contain an inner ring body in the MEMS structure, the present application shortens the length of the cantilever beam from the fixed end to the free end by setting one or more inner ring bodies, thereby reducing the probability of warping of the diaphragm of the piezoelectric composite vibration layer 20. Moreover, since the probability of warping of the diaphragm of the piezoelectric composite vibration layer 20 is reduced, the process difficulty of the MEMS structure is reduced, and the yield and stability of the device are improved. In addition, the fixed end and the free end are freely designed in the MEMS structure in the present application, so that the sensitivity of the multiple cantilever beam structures in the piezoelectric composite vibration layer 20 is effectively improved.

[0048] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A MEMS structure, characterized in that: include: The substrate comprises an outer ring body and a first inner ring body disposed in the outer ring body and spaced apart from the outer ring body, wherein a cavity is provided between the outer ring body and the first inner ring body and inside the first inner ring body; A piezoelectric composite vibration layer is formed above the substrate, and the piezoelectric composite vibration layer includes a fixed end connected to the first inner ring body and a free end suspended above the cavity; Wherein, the substrate further comprises one or more first support plates, a first end of the first support plate is connected to the outer ring body, a second end of the first support plate is connected to the first inner ring body, and the first support plate, the outer ring body, and the first inner ring body form a plurality of the cavities; Wherein, the substrate comprises: silicon or a silicon-based compound or a silicon-based derivative.

2. The MEMS structure according to claim 1, characterized in that: The piezoelectric composite vibration layer includes one or more first diaphragms arranged at intervals along the circumference of the first inner ring body, the fixed end of the first diaphragm is connected to the first inner ring body, and the free end of the first diaphragm extends toward the center of the piezoelectric composite vibration layer.

3. The MEMS structure according to claim 1, characterized in that: The piezoelectric composite vibration layer includes one or more second diaphragms arranged at intervals along the circumference of the first inner ring body, the fixed end of the second diaphragm is connected to the first inner ring body, and the free end of the second diaphragm extends in a direction away from the center of the piezoelectric composite vibration layer.

4. The MEMS structure according to claim 3, characterized in that: The substrate further includes: a second inner ring body, the second inner ring body being located between the outer ring body and the first inner ring body; The projection contour of the free end of the second diaphragm in the vibration direction is located inside the second inner ring body.

5. The MEMS structure according to claim 1, characterized in that: The substrate further includes a second inner ring body, and the second inner ring body is located between the outer ring body and the first inner ring body.

6. The MEMS structure according to claim 5, characterized in that: The middle end of the first support plate is connected to the second inner ring body, wherein the first support plate, the outer ring body, the first inner ring body, and the second inner ring body form a plurality of cavities.

7. The MEMS structure according to claim 5, characterized in that: The piezoelectric composite vibration layer includes one or more third diaphragms arranged at intervals along the circumference of the second inner ring body, the fixed end of the third diaphragm is connected to the second inner ring body, and the free end of the third diaphragm extends in a direction away from the center of the piezoelectric composite vibration layer.

8. The MEMS structure according to claim 7, characterized in that: The projection contour of the free end of the third diaphragm in the vibration direction is located inside the outer ring body.

9. The MEMS structure according to claim 1, characterized in that: The piezoelectric composite vibration layer has a plurality of gaps, positions of the gaps correspond to positions of the first supports, and widths of the gaps are greater than thicknesses of the first support plates.

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