MEMS structure forming method and MEMS structure

Abstract

The invention relates to an MEMS structure forming method and an MEMS structure, and the method comprises the steps: forming a graphical isolation layer on the front surface of a substrate, and enabling the isolation layer to expose a part of the front surface of the substrate; forming a vibration film on the surface of the isolation layer and the exposed part of the front surface of the substrate, the vibration film comprising a support part and a vibration part which are connected, the support part being located on the exposed part of the front surface of the substrate and the side surface of the isolation layer, and the vibration part being located on the top surface of the isolation layer; forming a sacrificial layer on the surface of the vibrating diaphragm; forming a back electrode plate on the sacrificial layer; forming a plurality of mutually independent sound holes in a first preset area of the back polar plate, wherein the sound holes penetrate through the back polar plate and expose the sacrificial layer; forming an opening from one side of the back surface of the substrate, the opening corresponding to the isolation layer up and down and penetrating through the substrate to expose the isolation layer; and taking the sound hole and the opening as release windows, and simultaneously removing the isolation layer and the sacrificial layer between the vibration part and the back polar plate. According to the invention, collapse of the MEMS structure can be avoided, and the MEMS structure has good performance.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for forming a MEMS structure and a MEMS structure. Background Art

[0002] Micro Electro Mechanical Systems (MEMS) have the outstanding advantages of small size, light weight, low energy consumption, high performance and easy integration. They are the irreplaceable key core components of various smart sensors in the world today.

[0003] However, in the existing methods for preparing MEMS structures, it is easy to over-etch the sacrificial layer in order to form a cavity, causing the MEMS structure to collapse. From a process point of view, the probability of over-etching can be reduced by reducing the time of etching the sacrificial layer, but this will cause the sacrificial layer to remain, resulting in the performance of the MEMS structure being affected. Therefore, it is difficult for the existing methods for preparing MEMS structures to avoid the collapse of the MEMS structure while taking into account the performance of the MEMS structure. Summary of the invention

[0004] The technical problem solved by the present invention is to provide a method for forming a MEMS structure and a MEMS structure, which can avoid collapse of the MEMS structure while taking into account good performance.

[0005] In order to solve the above technical problems, the technical solution of the present invention provides a method for forming a MEMS structure, comprising: forming a patterned isolation layer on the front side of a substrate, the isolation layer exposing a portion of the front side of the substrate; forming a vibration membrane on the surface of the isolation layer and the exposed portion of the front side of the substrate, the vibration membrane comprising a connected support portion and a vibration portion, the support portion being located on the exposed portion of the front side of the substrate and the side of the isolation layer, and the vibration portion being located on the top surface of the isolation layer; forming a sacrificial layer on the surface of the vibration membrane; forming a back plate on the sacrificial layer; forming a plurality of independent acoustic holes in a first preset area of the back plate, the acoustic holes penetrating the back plate and exposing the sacrificial layer, the first preset area corresponding to the vibration portion up and down; forming an opening from the back side of the substrate, the opening corresponding to the isolation layer up and down, and penetrating the substrate to expose the isolation layer; using the acoustic holes and the opening as release windows, and removing the isolation layer and the sacrificial layer between the vibration portion and the back plate at the same time.

[0006] Optionally, a cross-sectional area of the opening in the horizontal direction is smaller than a cross-sectional area of the isolation layer in the horizontal direction.

[0007] Optionally, it further includes: before forming the back plate, forming a first insulating layer on the surface of the sacrificial layer, and the back plate is located on the surface of the second preset area of the first insulating layer; forming a second insulating layer on the surface of the back plate and the exposed surface of the first insulating layer; the sound holes also penetrate through the first insulating layer and the second insulating layer.

[0008] Optionally, after forming the back plate on the sacrificial layer and before forming a plurality of relatively independent sound holes in the first preset area of the back plate, it further includes: forming a plurality of anti-sticking grooves in the back plate and the sacrificial layer, wherein the back plate is located on the surface of the second preset area of the sacrificial layer; forming a second insulating layer on the surface of the back plate and in the anti-sticking grooves, the second insulating layer fills the anti-sticking grooves, and the surface of the second insulating layer is higher than the back plate; the sound holes also penetrate through the second insulating layer and the back plate, and the sound holes are located between adjacent anti-sticking grooves.

[0009] Optionally, the back plate has a back plate projection on the front surface of the substrate, the back plate projection corresponds to the second preset area, and the back plate projection partially overlaps with the projection of the support portion on the front surface of the substrate.

[0010] Optionally, after forming the second insulating layer and before forming the sound holes, it further includes: forming a first conductive structure outside the second preset area, the bottom of the first conductive structure contacts the surface of the support portion, and the top of the first conductive structure is exposed by the second insulating layer; forming a second conductive structure in the second insulating layer of the second preset area, the bottom of the second conductive structure contacts the surface of the back plate, and the top of the second conductive structure is exposed by the second insulating layer.

[0011] Optionally, after forming the sound holes and before forming the opening penetrating the substrate, it further includes: thinning the substrate from the back surface of the substrate.

[0012] Optionally, the top surface of the isolation layer is a wavy surface, and the vibrating portion is a corrugated structure.

[0013] Optionally, the thickness of the isolation layer is less than the thickness of the sacrificial layer between the vibrating portion and the back plate.

[0014] Correspondingly, the technical solution of the present invention further provides a MEMS structure, including: a substrate; a vibrating membrane, including a connected supporting portion and a vibrating portion, a part of the supporting portion is located on the front surface of the substrate, the vibrating portion is higher than the front surface of the substrate and is spaced apart from the front surface of the substrate; a back plate, located on the vibrating membrane and spaced apart from the vibrating portion; a sacrificial layer, located between the supporting portion and the back plate; a plurality of mutually independent sound holes, the sound holes penetrate through the back plate and communicate with the spaced-apart space between the vibrating portion and the back plate; an opening, penetrating through the substrate and communicating with the spaced-apart space between the vibrating portion and the substrate.

[0015] Compared with the prior art, the technical solution of the embodiment of the present invention has the following beneficial effects:

[0016] In the formation method of the MEMS structure provided by the technical solution of the present invention and the MEMS structure, since a patterned isolation layer is formed on the front surface of the substrate, and a vibrating membrane is formed on the surface of the isolation layer and the exposed part of the front surface of the substrate, the supporting basis of the supporting portion of the vibrating membrane is the substrate (the supporting portion is supported on the front surface of the substrate). The wet etching process for removing the isolation layer and part of the sacrificial layer has a large etching selectivity for the materials of the two and the material of the substrate, so it can fully etch the isolation layer and the sacrificial layer to avoid residual contamination while reducing the risk of collapse of the vibrating membrane. Moreover, since a patterned isolation layer is formed on the front surface of the substrate, a vibrating membrane is formed on the surface of the isolation layer and the exposed part of the front surface of the substrate, and on this basis, a sacrificial layer is formed on the vibrating membrane and a back plate is formed on the sacrificial layer, it is possible to adjust the thickness of the isolation layer to cooperate with the etching of the sacrificial layer while ensuring that the distance between the vibrating portion and the back plate meets the requirements. Thus, when removing the isolation layer, the sacrificial layer can be appropriately etched, thereby improving the problem of over-etching, reducing the risk of collapse of the back plate, and at the same time avoiding the residual problem of the isolation layer and the sacrificial layer. In summary, it is possible to avoid the collapse of the MEMS structure while taking into account good performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figures 1 to 4 is a schematic structural diagram of each step of a preparation method of a MEMS structure;

[0018] Figure 5 is a schematic structural diagram of the MEMS structure in a collapsed state;

[0019] Figures 6 to 15 is a schematic cross-sectional structural diagram of each step of the formation method of the MEMS structure according to an embodiment of the present invention;

[0020] Figures 16 to 22 is a schematic cross-sectional structural diagram of each step of the formation method of the MEMS structure according to another embodiment of the present invention.

[0021] Description of reference numerals:

[0022] 10, 100-substrate; 11-release opening; 21-first sacrificial layer; 22-second sacrificial layer; 23-stacked structure; 24-acoustic hole; 25, 120-vibration membrane; 101-front; 102-back; 110-isolation layer; 121-support part; 122-vibration part; 130-sacrificial layer; 131-anti-sticking groove; 140-first insulating layer; 150, 250-back plate; 160, 260-second insulating layer; 171, 271-first conductive structure; 172, 272-second conductive structure; 180, 280-acoustic hole; 190, 290-opening. DETAILED DESCRIPTION

[0023] As described in the background art, it is difficult for the existing MEMS structure preparation method to avoid the collapse of the MEMS structure while taking into account the performance of the MEMS structure. Figures 1 to 5 Provide explanation.

[0024] Figures 1 to 4 It is a structural schematic diagram of each step of the preparation method of a MEMS structure. Figure 5 It is a schematic diagram of a MEMS structure in a collapsed state during a method for preparing the MEMS structure.

[0025] Please refer to Figure 1 and Figure 2 , Figure 1 yes Figure 2 A top view of Figure 2 yes Figure 1 Schematic diagram of the cross-sectional structure along the A1-A2 direction, a MEMS structure to be released is formed on the front side of the substrate 10, including: a first sacrificial layer 21 is deposited on the surface of the substrate 10; a patterned vibration membrane 25 is formed on the surface of the first sacrificial layer 21; a second sacrificial layer 22 is formed on the surface of the vibration membrane 25 and the exposed surface of the first sacrificial layer 21; a stacking structure 23 is formed on the second sacrificial layer 22, the stacking structure 23 includes an insulating layer-back plate-insulating layer stacked from bottom to top; a plurality of through acoustic holes 24 are formed in the stacking structure 23, the acoustic holes 24 are opposite to the vibration membrane 25, and the bottom of the acoustic holes 24 exposes the second sacrificial layer 22.

[0026] Next, please refer to Figure 3 The substrate 10 is etched from the back side of the substrate 10 to form a release opening 11 in the substrate 10 . The release opening 11 exposes the first sacrificial layer 21 .

[0027] Please refer to Figure 4, using the acoustic hole 24 and the release opening 11 as release windows, wet etching is performed on the first sacrificial layer 21 and the second sacrificial layer 22 to remove portions of the first sacrificial layer 21 and the second sacrificial layer 22 above the release opening 11 .

[0028] In the above-mentioned method for preparing the MEMS structure, the first sacrificial layer 21 and the second sacrificial layer 22 remaining above both sides of the release opening 11 are used as side walls to support the vibration membrane 25 and the stacked structure 23 respectively.

[0029] However, due to the large size difference between the acoustic hole 24 and the release opening 11, when the first sacrificial layer 21 and the second sacrificial layer 22 are etched through the acoustic hole 24 and the release opening 11, the etching rates of the first sacrificial layer 21 and the second sacrificial layer 22 are different. Moreover, in the direction parallel to the surface of the substrate 10, the MEMS structure is not completely symmetrical (e.g., Figure 1 ), and deep silicon etching is required from the back side of the substrate 10 to form a release opening 11 exposing the first sacrificial layer 21 at the bottom, which will make the sidewall of the release opening 11 more inclined, and its width dimension on the front side of the substrate 10 will be larger than its width dimension on the back side of the substrate 10 (as shown in FIG. Figure 3 As shown in FIG. 1 , when the first sacrificial layer 21 and the second sacrificial layer 22 are actually etched, over-etching is very likely to occur, resulting in local collapse of the MEMS structure (as shown in FIG. 1 ). Figure 5 shown) problem.

[0030] In order to reduce the above-mentioned collapse risk, the probability of over-etching can be reduced by reducing the wet etching time from a process point of view. However, insufficient etching will cause the first sacrificial layer 21 and the second sacrificial layer 22 to remain between the vibrating membrane 25 and the substrate 10, between the vibrating membrane 25 and the back plate, and between the back plate and the sound hole 24 in the central structural area of the MEMS structure (the area that needs to be released), which will not only affect the vibration of the vibrating membrane 25, causing a reduction in the sensitivity of the microphone and other performance, but also affect the microphone's ability to receive sound signals. As a result, the performance of the MEMS structure deteriorates.

[0031] Therefore, it is difficult to avoid the collapse of the MEMS structure while taking into account the performance of the MEMS structure.

[0032] To solve the above technical problems, the technical solution of the present invention provides a method for forming a MEMS structure and a MEMS structure. By forming a patterned isolation layer on the front surface of the substrate and forming a vibrating membrane on the surface of the isolation layer and the exposed part of the front surface of the substrate, on the one hand, the vibrating membrane can become a self-supporting structure supported on the front surface of the substrate after releasing the isolation layer and the sacrificial layer; on the other hand, the thickness of the isolation layer can be adjusted to cooperate with the sacrificial layer to reduce the risk of over-etching. Thus, the risk of collapse of the back plate is reduced. At the same time, the problem of residue of the isolation layer and the sacrificial layer is avoided to take into account good performance.

[0033] Therefore, the support basis of the support part of the vibrating membrane is the substrate (the support part is supported on the front surface of the substrate). The wet etching process for removing the isolation layer and part of the sacrificial layer has a large etching selectivity ratio for the materials of the two and the material of the substrate. Therefore, while fully etching the isolation layer and the sacrificial layer to avoid residual contamination, the risk of collapse of the vibrating membrane can be reduced. Moreover, since a patterned isolation layer is formed on the front surface of the substrate, a vibrating membrane is formed on the surface of the isolation layer and the exposed part of the front surface of the substrate, and on this basis, a sacrificial layer is formed on the surface of the vibrating membrane, and a back plate is formed on the sacrificial layer. Therefore, while ensuring that the distance between the vibrating part and the back plate meets the requirements, the thickness of the isolation layer can be adjusted to cooperate with the etching of the sacrificial layer. Thus, while removing the isolation layer, the sacrificial layer can be properly etched. Thereby, the problem of over-etching is improved, the risk of collapse of the back plate is reduced, and at the same time, the problem of residue of the isolation layer and the sacrificial layer is avoided. In summary, good performance can be taken into account while avoiding the collapse of the MEMS structure.

[0034] To make the above objects, features, and beneficial effects of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] The terms "first", "second", "third", "fourth", etc. (if any) in the description, claims and drawings of the present invention are used to distinguish similar objects and do not necessarily describe a specific order or sequence. It should be understood that such data used can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order different from those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily limit to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices. In addition, directional terms such as above, below, up, down, upward, downward, left, right, etc. are used with respect to exemplary embodiments as shown in the figures, where the upward or upper direction is towards the top of the corresponding figure and the downward or lower direction is towards the bottom of the corresponding figure.

[0036] Figures 6 to 15 is a schematic cross-sectional structure diagram of each step of a method for forming a MEMS structure according to an embodiment of the present invention.

[0037] Please refer to Figure 6 , and provide a substrate 100.

[0038] In this embodiment, the substrate 100 is a silicon substrate.

[0039] In other embodiments, the substrate may include at least one of the following materials: Ge, SiGe, SiC, SiGeC, InAs, GaAs, InP, InGaAs or other III / V compound semiconductors. Or the substrate may also include silicon on insulator (SOI), stacked silicon on insulator (SSOI), stacked silicon germanide on insulator (S-SiGeOI), silicon germanide on insulator (SiGeOI) or germanium on insulator (GeOI), etc.

[0040] The substrate 100 has opposite front surface 101 and back surface 102.

[0041] Please continue to refer to Figure 6 , and form a patterned isolation layer 110 on the front surface 101 of the substrate 100, and the isolation layer 110 exposes a part of the front surface 101 of the substrate 100.

[0042] Since the cavity of the MEMS structure is released by removing the patterned isolation layer 110 subsequently, enabling the vibration membrane 120 to be suspended in the cavity for vibration, the size of the patterned isolation layer 110 actually defines the effective vibration area of the vibration membrane 120. Thus, through the isolation layer 110 with controllable shape, the effective vibration area of the vibration membrane 120 can be precisely controlled. The effective vibration area of the vibration membrane 120 is related to the size design of the MEMS structure. Therefore, the size of the patterned isolation layer 110 depends on the size design of the fabricated MEMS structure. Here, the specific size of the patterned isolation layer 110 is not limited, and the size of the appropriate patterned isolation layer 110 can be selected according to the size of the required MEMS device. As an example, the cross-sectional diameter of the patterned isolation layer 110 on the first surface 101 of the substrate 100 can be 700 to 800 micrometers.

[0043] On the one hand, the isolation layer 110 provides a surface for the subsequent deposition of the material of the vibration membrane 120, providing support for forming the self-supporting vibration membrane 120. On the other hand, the isolation layer 110 can be used as an etch stop layer when forming the opening 190 subsequently, thereby protecting the vibration membrane 120 from being damaged during the etching process of forming the opening 190.

[0044] Furthermore, the thickness range of the isolation layer 110 is 0.1 to 10 micrometers. In addition, the thickness of the vibration membrane 120 is also one of the factors determining the thickness of the isolation layer 110. Specifically, the thickness of the isolation layer 110 cannot be too high to avoid the side wall surface of the isolation layer 110 not being covered by the vibration membrane 120 when depositing the material of the vibration membrane 120.

[0045] Furthermore, the formation method of the isolation layer 110 includes: depositing an isolation material layer (not shown) on the front surface 101 of the substrate 100; forming a patterned first mask layer (not shown) on the surface of the isolation material layer, and the first mask layer exposes a part of the surface of the isolation material layer; using the first mask layer as a mask to etch the isolation material layer until a part of the front surface 101 of the substrate 100 is exposed.

[0046] Among them, the isolation material layer can be deposited by chemical vapor deposition process or physical vapor deposition process, and the isolation material layer can be etched by dry etching process or wet etching process.

[0047] In this embodiment, the top surface of the isolation layer 110 is a plane.

[0048] In other embodiments, the top surface of the isolation layer is a wavy surface.

[0049] Specifically, the material of the isolation layer 110 can include: silicon oxide, organic polymer, silicon carbide, titanium dioxide, or other metal oxides, etc.

[0050] Please refer to Figure 7 to form a vibrating membrane 120 on the surface of the isolation layer 110 and the exposed part of the front surface 101 of the substrate 100.

[0051] The vibrating membrane 120 includes a support portion 121 and a vibrating portion 122. Among them, the support portion 121 is located on the exposed part of the front surface 101 of the substrate 100 and the side surface of the isolation layer 110, and the vibrating portion 122 is located on the top surface of the isolation layer 110. Thus, the support portion 121 of the vibrating membrane 120 is connected to the front surface 101 of the substrate 100, and the vibrating portion 122 of the vibrating membrane 120 is lifted relative to the front surface 101 of the substrate 100. Therefore, after the isolation layer 110 is removed subsequently, the vibrating membrane 120 becomes a self-supporting structure that is self-supported by the surface of the substrate 100 and the vibrating portion 122 is suspended above the front surface 101 of the substrate 100.

[0052] Furthermore, the thickness range of the vibrating membrane 120 is 0.1 micrometer to 1 micrometer.

[0053] The formation process of the vibrating membrane 120 can adopt chemical vapor deposition process or physical vapor deposition process.

[0054] In other embodiments, the top surface of the isolation layer is a wavy surface. Correspondingly, the vibrating portion is a corrugated structure, so as to reduce the residual stress generated during the vibration process when the MEMS structure works.

[0055] Specifically, the vibrating membrane 120 is a conductive material. Further, the material of the vibrating membrane 120 can be doped polysilicon, single crystal silicon, a composite layer of silicon nitride and metal, or graphene, etc.

[0056] Please refer to Figure 8 to form a sacrificial layer 130 on the surface of the vibrating membrane 120.

[0057] Among them, the surface of the sacrificial layer 130 is higher than that of the vibrating membrane 120. That is to say, the surface of the sacrificial layer 130 is higher than the surface of the vibrating portion 122.

[0058] In one embodiment, the thickness of the sacrificial layer 130 between the subsequently formed vibrating portion 122 and the back plate 150 is greater than the thickness of the isolation layer 110. Therefore, on the one hand, it ensures that there is a large gap between the vibrating membrane 120 and the back plate 150, which helps to reduce the residual stress in the manufacturing process of the vibrating membrane 120 and avoid deformation or rupture. On the other hand, it avoids the thickness of the isolation layer 110 being too large and reducing the step coverage rate of the deposition of the vibrating membrane 120.

[0059] Among them, the process of forming the sacrificial layer 130 can be chemical vapor deposition or physical vapor deposition.

[0060] Specifically, the sacrificial layer 130 is an insulating material. Further, the material of the sacrificial layer 130 may be silicon oxide, a polymer material (such as polyimide), silicon nitride, etc.

[0061] Please refer to Figure 9 , and a first insulating layer 140 is formed on the surface of the sacrificial layer 130. Among them, the process of forming the first insulating layer 140 may be a chemical vapor deposition process or a physical vapor deposition process.

[0062] Specifically, the material of the first insulating layer 140 may be silicon oxide, silicon nitride, aluminum oxide, hafnium oxide, titanium oxide, or a composite insulating layer (such as silicon oxide and silicon nitride), etc.

[0063] Please refer to Figure 10 , and a back plate 150 is formed on the sacrificial layer 130.

[0064] Since the first insulating layer 140 is formed on the surface of the sacrificial layer 130 before forming the back plate 150, in this embodiment, the back plate 150 is formed on the surface of the first insulating layer 140.

[0065] The back plate 150 is located on the surface of the second preset area of the first insulating layer 140, so that the back plate 150 exposes a part of the surface of the first insulating layer 140. Among them, the second preset area has a second area projection on the first surface 101 of the substrate 100. The first side of the second area projection corresponds to the first side of the vibration part 122 up and down, the second side of the second area projection extends beyond the second side of the vibration part 122, and the extended part of the second area projection (for the sake of understanding, the part where the second side of the second area projection extends beyond the second side of the vibration part 122 is called the extended part of the second area projection) partially overlaps with the support part 121 located on the second side of the vibration part 122. That is to say, the second preset area corresponds to the vibration part 122 up and down, and the area of the second preset area is larger than the area of the vibration part 122. In addition, the part of the area of the second preset area that is larger than the vibration part 122 corresponds to the support part 121; among them, the first side and the second side refer to the left and right sides as shown in Figures 6 - 22 The left and right sides shown, and those skilled in the art can select appropriate relative sides for setting. Here, it is only for example and not limited.

[0066] By forming the back plate 150 on the surface of the first insulating layer 140, since there is the first insulating layer 140 between the back plate 150 and the vibration film 120 corresponding to the subsequent formed MEMS structure, the short - circuit problem between the back plate 150 and the vibration film 120 caused by adhesion between them can be prevented.

[0067] Further, the thickness range of the back plate 150 is from 0.1 micrometer to 1 micrometer. Specifically, the thickness of the back plate 150 can be the same as that of the vibrating membrane 120, or the thickness of the back plate 150 can be less than that of the vibrating membrane 120. Those skilled in the art can select appropriate film layer thicknesses according to specific situations, which are not limited herein.

[0068] Further, the method for forming the back plate 150 on the surface of the first insulating layer 140 includes: forming a material layer (not shown) of the back plate 150 on the surface of the first insulating layer 140; forming a patterned second mask layer (not shown) on the surface of the material layer of the back plate 150, and the second mask layer exposes part of the surface of the material layer of the back plate 150; using the second mask layer as a mask, patterning and etching the material layer of the back plate 150 until the surface of the first insulating layer 140 is exposed. Among them, a chemical vapor deposition process or a physical vapor deposition process can be used to form the material layer of the back plate 150, and a dry etching process or a wet etching process can be used to etch the material layer of the back plate 150. The back plate 150 is patterned, and the area of the formed back plate 150 is larger than the area of the vibrating part 122 of the vibrating membrane 120. In one embodiment, the back plate 150 has a back plate 150 projection on the front surface 101 of the substrate 100, and the back plate 150 projection partially overlaps with the projection of the support part 121 on the front surface 101 of the substrate 100. Specifically, the first side of the back plate 150 can correspond to the first side of the vibrating part 122 of the vibrating membrane 120 up and down, the second side of the back plate 150 projects beyond the second side of the vibrating part 122 on the front surface 101 of the substrate, and partially overlaps with the support part 121 located on the second side of the vibrating part 122. Therefore, the back plate 150 above part of the support part 121 can be used to contact the subsequently formed second conductive structure 172 without affecting the effective working area of the MEMS structure. At the same time, there is still a part of the upper space of the support part 121 not blocked by the back plate 150, so that the first conductive structure 171 that contacts the vibrating membrane 120 and is separated from the back plate 150 can be formed subsequently.

[0069] Specifically, the back plate 150 is made of a conductive material. Further, the material of the back plate 150 can be doped polysilicon, single crystal silicon, metal thin film, titanium nitride, graphene, etc.

[0070] Please refer to Figure 11 , and a second insulating layer 160 is formed on the surface of the back plate 150 and the exposed surface of the first insulating layer 140.

[0071] Among them, a chemical vapor deposition process or a physical vapor deposition process can be used to form the second insulating layer 160.

[0072] Specifically, the material of the second insulating layer 160 includes silicon oxide, silicon nitride, aluminum oxide, hafnium oxide, titanium oxide, or a composite insulating layer (such as silicon oxide and silicon nitride, etc.).

[0073] Next, please refer to Figure 12 , a first conductive structure 171 is formed in the second insulating layer 160 outside the second preset area, and a second conductive structure 172 is formed in the second insulating layer 160 within the second preset area.

[0074] Among them, the bottom of the first conductive structure 171 contacts the surface of the support portion 121, and the top of the first conductive structure 171 is exposed by the second insulating layer 160.

[0075] In this embodiment, the first conductive structure 171 is also located within the sacrificial layer 130, within the first insulating layer 140, and within the second insulating layer 160. Specifically, outside the second preset area of the second insulating layer 160, at least one first conductive hole 171 sequentially passes through the second insulating layer 160, the first insulating layer 140, and the sacrificial layer 130 to reach the support portion 121 of the vibrating membrane 120.

[0076] Furthermore, the top of the first conductive structure 171 protrudes relative to the surface of the second insulating layer 160. Specifically, at least one second conductive hole 172 within the second preset area of the second insulating layer 160 sequentially passes through the second insulating layer 160 to reach the back plate 150.

[0077] Among them, the bottom of the second conductive structure 172 contacts the surface of the back plate 150, and the top of the second conductive structure 172 is exposed by the second insulating layer 160.

[0078] Furthermore, the top of the second conductive structure 172 protrudes relative to the surface of the second insulating layer 160.

[0079] In one embodiment, the method for forming the first conductive structure 171 includes: etching the first insulating layer 140, the second insulating layer 160, and the sacrificial layer 130 until the surface of the support portion 121 is exposed to form a first conductive opening (not shown); filling the material of the first conductive structure 171 in the first conductive opening.

[0080] In one embodiment, the method for forming the second conductive structure 172 includes: etching the second insulating layer 160 until the surface of the back plate 150 is exposed to form a second conductive opening (not shown); filling the material of the second conductive structure 172 in the second conductive opening. Preferably, the second conductive opening is located above the support portion 121 to prevent the second conductive structure 172 from affecting the effective working area of the MEMS structure.

[0081] In addition, according to specific requirements, the materials of the first conductive structure 171 and the second conductive structure 172 can be filled in the same step or separately.

[0082] Further, the material of the first conductive structure 171 includes at least one of aluminum, copper, gold, titanium, tungsten, titanium nitride, and silver.

[0083] Further, the material of the second conductive structure 172 includes at least one of aluminum, copper, gold, titanium, tungsten, titanium nitride, and silver.

[0084] Please refer to Figure 13 , then, a plurality of mutually independent sound holes 180 are formed in the first preset area of the back plate 150. Among them, the first preset area corresponds to the vibration part 122 of the vibration membrane 120 up and down.

[0085] The sound holes 180 penetrate through the back plate 150 and expose the sacrificial layer 130.

[0086] In this embodiment, the sound holes 180 also penetrate through the first insulating layer 140 and the second insulating layer 160.

[0087] Specifically, the size range of the sound holes 180 in the horizontal direction is 3 micrometers to 20 micrometers.

[0088] In addition, the sizes of the respective sound holes 180 among the plurality of sound holes 180 may be the same or different, and the specific sizes of the respective sound holes 180 are determined according to product requirements.

[0089] Further, the method for forming a plurality of mutually independent sound holes 180 includes: etching the first insulating layer 140, the sacrificial layer 130, and the second insulating layer 160. Specifically, a dry etching process or a wet etching process can be used for etching.

[0090] Please refer to Figure 14 , after forming the sound holes 180, the substrate 100 is thinned from the back surface 102 of the substrate 100.

[0091] By thinning the substrate 100, the etching depth for forming the opening 190 can be reduced, and an opening 190 with a more accurate pattern can be formed.

[0092] Further, the substrate 100 is thinned to 200 micrometers to 600 micrometers.

[0093] The process for thinning the substrate 100 can be a chemical mechanical polishing process.

[0094] In other embodiments, this thinning step may not be performed either.

[0095] Please continue to refer to Figure 14 , after thinning the substrate 100 from the back surface 102 of the substrate 100, an opening 190 is formed on one side of the back surface 102 of the substrate 100. The opening 190 corresponds to the isolation layer 110 up and down, and penetrates through the substrate 100 to expose the isolation layer 110.

[0096] Specifically, the substrate 100 is etched from the back side 102 of the substrate 100 until the isolation layer 110 is exposed, thereby forming an opening 190 penetrating the substrate 100 .

[0097] The opening 190 is used as a release window to release the isolation layer 110 and the sacrificial layer 130 later.

[0098] Preferably, the cross-sectional area of the opening 190 in the horizontal direction is smaller than the cross-sectional area of the isolation layer 110 in the horizontal direction. Therefore, the risk of etching the portion of the substrate 100 in contact with the support portion 121 during the etching process for forming the opening 190 is reduced, further reducing the risk of collapse of the MEMS structure.

[0099] Specifically, the opening 190 may be formed by using a dry etching process or a wet etching process.

[0100] Please refer to Figure 15 , using the plurality of acoustic holes 180 and the opening 190 as release windows, and removing the isolation layer 110 and the sacrificial layer 130 between the vibration part 122 and the back plate 150 at the same time.

[0101] Since a patterned isolation layer 110 is formed on the front surface 101 of the substrate 100, and a vibration membrane 120 is formed on the surface of the isolation layer 110 and the exposed portion of the front surface 101 of the substrate 100, the support base of the support portion 121 of the vibration membrane 120 is the substrate 100 (the support portion 121 is supported on the front surface 101 of the substrate 100). The wet etching process for removing the isolation layer 110 and part of the sacrificial layer 130 can have a greater etching selectivity to the materials of the two and the material of the substrate 100, so that the isolation layer 110 and the sacrificial layer 130 can be fully etched to avoid residual contamination while reducing the risk of collapse of the vibration membrane 120. Moreover, since a patterned isolation layer 110 is formed on the front side 101 of the substrate 100, a vibration membrane 120 is formed on the surface of the isolation layer 110 and the exposed portion of the front side 101 of the substrate 100, and on this basis, a sacrificial layer 130 is formed on the surface of the vibration membrane 120, and a back plate 150 is formed on the sacrificial layer 130, it is possible to coordinate the etching of the sacrificial layer 130 by adjusting the thickness of the isolation layer 110 while ensuring that the distance between the vibration part 122 and the back plate 150 meets the requirements, so that the sacrificial layer 130 can be properly etched while removing the isolation layer 110, thereby improving the problem of over-etching, reducing the risk of collapse of the back plate 150, and avoiding the problem of residual isolation layer 110 and sacrificial layer 130. In summary, it is possible to achieve good performance while avoiding the collapse of the MEMS structure.

[0102] Furthermore, a wet etching process is used to simultaneously remove the isolation layer 110 and the sacrificial layer 130 between the vibration part 122 and the back plate 150 .

[0103] Correspondingly, an embodiment of the present invention further provides a MEMS structure formed by the above method. Please continue to refer to Figure 15 , the MEMS structure includes: a substrate 100; a vibrating membrane 120, including a connected supporting portion 121 and a vibrating portion 122, a part of the supporting portion 121 is located on the front surface 101 of the substrate 100, the vibrating portion 122 is higher than the front surface 101 of the substrate 100, and there is a gap between the vibrating portion 122 and the front surface 101 of the substrate 100; a back plate 150, located on the vibrating membrane 120, and there is a gap between the back plate 150 and the vibrating portion 122; a sacrificial layer 130, located between the supporting portion 121 and the back plate 150; a plurality of independent sound holes 180, the sound holes 180 penetrate through the back plate 150 and communicate with the gap space between the vibrating portion 122 and the back plate 150; an opening 190, penetrating through the substrate 100 and communicating with the gap space between the vibrating portion 122 and the substrate 100.

[0104] The MEMS structure may specifically be a microphone.

[0105] It should be understood that since the MEMS structure of this embodiment is the corresponding structural embodiment of the above method embodiment, therefore, for the specific description of each structural feature in this embodiment, please refer to the relevant detailed explanations in the above method embodiment, which will not be repeated here. In addition, for the structural features of the deformation embodiment of this embodiment, please also refer to the detailed explanations in the deformation embodiment of the above method embodiment, which will not be repeated here.

[0106] Figures 16 to 22 is a schematic cross-sectional structure diagram of each step of the formation method of the MEMS structure of another embodiment of the present invention. The main difference between this embodiment and the Figures 6 to 15 shown embodiment lies in the different structures of the back plate, the sacrificial layer and the second insulating layer. The following will be described in detail with reference to the drawings.

[0107] Please continue to refer to Figure 8 on the basis of Figure 16 , and form a back plate 250 on the surface of the second preset area of the sacrificial layer 130. Wherein, the second preset area refers to: the area corresponding to the vibrating portion and the supporting portion on one side of the vibrating portion. The second preset area in this embodiment is the same as the second preset area in the foregoing embodiment, which will not be repeated here.

[0108] Further, the method for forming the back plate 250 on a partial surface of the sacrificial layer 130 includes: forming a material layer (not shown) of the back plate 250 on the surface of the sacrificial layer 130; forming a patterned second mask layer (not shown) on the surface of the material layer of the back plate 250, and the second mask layer exposes a partial surface of the material layer of the back plate 250; using the second mask layer as a mask to etch the material layer of the back plate 250 until the surface of the sacrificial layer 130 is exposed. Among them, the material layer of the back plate 250 can be formed by chemical vapor deposition process or physical vapor deposition process, and the material layer of the back plate 250 can be etched by dry etching process or wet etching process.

[0109] Please refer to Figure 17 , a plurality of anti-sticking grooves 131 are formed in the back plate 250 and the sacrificial layer 130.

[0110] The anti-sticking grooves 131 provide space for the material for filling the second insulating layer 260 subsequently, so that the formed second insulating layer 260 includes an anti-sticking structure.

[0111] Specifically, the size of the anti-sticking grooves 131 in the horizontal direction is 0.2 micrometers to 3 micrometers. The reason for making the size of the anti-sticking grooves 131 in the horizontal direction be 0.2 micrometers to 3 micrometers is that: the size of the anti-sticking grooves 131 cannot be too large, so as not to occupy too much area and affect the performance of the device, and the size of the anti-sticking grooves 131 cannot be too small, so as to avoid poor filling performance when depositing a film layer subsequently.

[0112] Further, the method for forming a plurality of anti-sticking grooves 131 in the back plate 250 and the sacrificial layer 130 includes: forming a third mask layer (not shown) on the surfaces of the back plate 250 and the exposed sacrificial layer 130, and the third mask layer exposes a partial surface of the back plate 250 on the vibrating part 122; using the third mask layer as a mask to etch the back plate 250 until the surface of the sacrificial layer 130 is exposed; then, continuing to etch the sacrificial layer 130 with the third mask layer until a plurality of anti-sticking grooves 131 are formed.

[0113] Please refer to Figure 18 , a second insulating layer 260 is formed on the surface of the back plate 250 and in the anti-sticking grooves 131, the second insulating layer 260 fills the anti-sticking grooves 131, and the surface of the second insulating layer 260 is higher than that of the back plate 250.

[0114] Since the second insulating layer 260 fills the anti-sticking grooves 131, therefore, the second insulating layer 260 includes an anti-sticking structure located in the sacrificial layer 130, and thus, the short-circuit problem caused by the adhesion between the back plate 250 and the vibrating membrane 120 can be prevented.

[0115] Specifically, forming the second insulating layer 260 on the surface of the backplate 250 and within the anti-sticking groove 131 includes a chemical vapor deposition process or a physical vapor deposition process.

[0116] Next, please refer to Figure 19 , a first conductive structure 271 is formed outside the second preset area, and a second conductive structure 272 is formed within the second insulating layer 260 of the second preset area.

[0117] Among them, the bottom of the first conductive structure 271 contacts the surface of the support portion 121, and the top of the first conductive structure 271 is exposed by the second insulating layer 260.

[0118] In this embodiment, the first conductive structure 271 is also located within the sacrificial layer 130 and the second insulating layer 260.

[0119] Furthermore, the top of the first conductive structure 271 protrudes relative to the surface of the second insulating layer 260. Specifically, outside the second preset area of the second insulating layer 260, at least one first conductive hole 271 sequentially penetrates the second insulating layer 260 and the sacrificial layer 130 to reach the support portion 121 of the vibration membrane 120.

[0120] Among them, the bottom of the second conductive structure 272 contacts the surface of the backplate 250, and the top of the second conductive structure 272 is exposed by the second insulating layer 260.

[0121] Furthermore, the top of the second conductive structure 272 protrudes relative to the surface of the second insulating layer 260. Specifically, within the second preset area of the second insulating layer 260, at least one second conductive hole 272 sequentially penetrates the second insulating layer 260 to reach the backplate 150.

[0122] In one embodiment, the forming method of the first conductive structure 271 includes: etching the second insulating layer 260 and the sacrificial layer 130 until the surface of the support portion 121 is exposed to form a first conductive opening (not shown); filling the material of the first conductive structure 271 in the first conductive opening.

[0123] In one embodiment, the forming method of the second conductive structure 272 includes: etching the second insulating layer 260 until the surface of the backplate 250 is exposed to form a second conductive opening (not shown); filling the material of the second conductive structure 272 in the second conductive opening. Preferably, the second conductive opening is located above the support portion 121 to prevent the second conductive structure 272 from affecting the effective working area of the MEMS structure.

[0124] Please refer to Figure 20, a plurality of independent acoustic holes 280 are formed in a first preset area of the back plate 250. Among them, the first preset area corresponds to the vibration part 122 up and down. And, the area of the second preset area is larger than the area of the first preset area. The acoustic holes 280 penetrate through the back plate 250 and expose the sacrificial layer 130.

[0125] In this embodiment, the acoustic holes 280 also penetrate through the second insulating layer 260, and the acoustic holes 280 are located between adjacent anti-sticking grooves 131.

[0126] Furthermore, the method for forming a plurality of independent acoustic holes 280 includes: etching the sacrificial layer 130 and the second insulating layer 260. Specifically, a dry etching process or a wet etching process can be used for etching.

[0127] Please refer to Figure 21 , after forming the acoustic holes 280, the substrate 100 is thinned from the back surface 102 of the substrate 100.

[0128] The process for thinning the substrate 100 can be a chemical mechanical polishing process.

[0129] Please continue to refer to Figure 21 , an opening 290 is formed on one side of the back surface 102 of the substrate 100. The opening 290 corresponds to the isolation layer 110 up and down, and penetrates through the substrate 100 to expose the isolation layer 110.

[0130] Specifically, the substrate 100 is etched from one side of the back surface 102 of the substrate 100 until the isolation layer 110 is exposed, and an opening 290 penetrating through the substrate 100 is formed.

[0131] For the specific method of forming the opening 290, reference can be made to Figures 6 to 15 the relevant explanations in the illustrated embodiment, which will not be elaborated here.

[0132] Please refer to Figure 22 , using a plurality of acoustic holes 280 and the opening 290 as release windows, the isolation layer 110 and the sacrificial layer 130 between the vibration part 122 and the back plate 250 are removed simultaneously.

[0133] Similar to Figures 6 to 15 the illustrated embodiment, the method for forming the MEMS structure in this embodiment can also avoid the collapse of the MEMS structure while taking into account good performance, which will not be elaborated here.

[0134] Furthermore, a wet etching process is used to remove the isolation layer 110 and the sacrificial layer 130 between the vibration part 122 and the back plate 250 simultaneously.

[0135] Correspondingly, another embodiment of the present invention also provides a MEMS structure formed by the above method. Please continue to refer to Figure 22, the MEMS structure includes: a substrate 100; a vibrating membrane 120 including a connected support portion 121 and a vibrating portion 122, with a part of the support portion 121 located on the front surface 101 of the substrate 100, the vibrating portion 122 being higher than the front surface 101 of the substrate 100 and spaced apart from the front surface 101 of the substrate 100; a back plate 250 located on the vibrating membrane 120 and spaced apart from the vibrating portion 122; a sacrificial layer 130 located between the support portion 121 and the back plate 250; a plurality of mutually independent sound holes 280 that penetrate the back plate 250 and communicate the spaced-apart space between the vibrating portion 122 and the back plate 250; and an opening 290 that penetrates the substrate 100 and communicates the spaced-apart space between the vibrating portion 122 and the substrate 100.

[0136] The MEMS structure may specifically be a microphone.

[0137] It should be understood that since the MEMS structure of this embodiment is the corresponding structural embodiment of the above method embodiment, for the specific descriptions of the structural features in this embodiment, please refer to the relevant detailed explanations in the above method embodiment and will not be elaborated here. In addition, for the structural features of the modified embodiments of this embodiment, please also refer to the detailed explanations in the modified embodiments of the above method embodiment and will not be elaborated here.

[0138] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A method for forming a MEMS structure, characterized in that, Comprising: Forming a patterned isolation layer on the front side of the substrate, the isolation layer exposing a part of the front side of the substrate; Forming a vibrating membrane on the surface of the isolation layer and the exposed part of the front side of the substrate, the vibrating membrane including a connected support part and a vibrating part, the support part being located on the exposed part of the front side of the substrate and the side surface of the isolation layer, and the vibrating part being located on the top surface of the isolation layer; Forming a sacrificial layer on the surface of the vibrating membrane; Forming a back plate on the sacrificial layer; Forming a plurality of mutually independent sound holes in a first preset area of the back plate, the sound holes penetrating through the back plate and exposing the sacrificial layer, the first preset area corresponding to the vibrating part up and down; Forming an opening from the back side of the substrate, the opening corresponding to the isolation layer up and down and penetrating through the substrate to expose the isolation layer; Using the sound holes and the opening as release windows to simultaneously remove the isolation layer and the sacrificial layer between the vibrating part and the back plate.

2. The method for forming the MEMS structure according to claim 1, wherein The cross-sectional area of the opening in the horizontal direction is smaller than the cross-sectional area of the isolation layer in the horizontal direction.

3. The method for forming the MEMS structure according to claim 1, characterized in that Further comprising: Before forming the back plate, forming a first insulating layer on the surface of the sacrificial layer, the back plate being located on the surface of a second preset area of the first insulating layer; Forming a second insulating layer on the surface of the back plate and the exposed surface of the first insulating layer; The sound holes also penetrate through the first insulating layer and the second insulating layer.

4. The method for forming the MEMS structure according to claim 1, wherein After forming the back plate on the sacrificial layer and before forming a plurality of relatively independent sound holes in the first preset area of the back plate, further comprising: Forming a plurality of anti-sticking grooves in the back plate and the sacrificial layer, wherein the back plate is located on the surface of a second preset area of the sacrificial layer; Forming a second insulating layer on the surface of the back plate and in the anti-sticking grooves, the second insulating layer filling the anti-sticking grooves, and the surface of the second insulating layer being higher than the back plate; The sound holes also penetrate through the second insulating layer and the back plate, and the sound holes are located between adjacent anti-sticking grooves.

5. The method for forming the MEMS structure according to claim 3 or 4, characterized in that, The back plate has a back plate projection on the front side of the substrate, the back plate projection corresponding to the second preset area, and the back plate projection partially overlapping with the projection of the support part on the front side of the substrate.

6. The method for forming the MEMS structure according to claim 5, wherein After forming the second insulating layer and before forming the sound holes, further comprising: Forming a first conductive structure outside the second preset area, the bottom of the first conductive structure contacting the surface of the support part, and the top of the first conductive structure being exposed by the second insulating layer; Forming a second conductive structure in the second insulating layer of the second preset area, the bottom of the second conductive structure contacting the surface of the back plate, and the top of the second conductive structure being exposed by the second insulating layer.

7. The method for forming the MEMS structure according to claim 1, characterized in that, After forming the sound holes and before forming the opening penetrating through the substrate, further comprising: thinning the substrate from the back side of the substrate.

8. The method for forming the MEMS structure according to claim 1, wherein, The top surface of the isolation layer is a wavy surface, and the vibrating part is a corrugated structure.

9. The method for forming the MEMS structure according to claim 1, wherein The thickness of the isolation layer is smaller than the thickness of the sacrificial layer between the vibrating part and the back plate.

10. A MEMS structure, characterized in that, Comprising: Substrate; The diaphragm includes a connected support part and a vibrating part. Part of the support part is located on the front side of the substrate. The vibrating part is higher than the front side of the substrate and is spaced apart from the front side of the substrate. The back plate is located on the diaphragm and is spaced apart from the vibrating part. The sacrificial layer is located between the support part and the back plate. A number of mutually independent sound holes penetrate through the back plate and communicate with the space between the vibrating part and the back plate. The opening penetrates through the substrate and communicates with the space between the vibrating part and the substrate.

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