MEMS silicon microphone structure and preparation method thereof

Abstract

The invention provides an MEMS silicon microphone structure and a preparation method thereof.In the preparation method, a sacrificial material layer, a vibrating diaphragm located in the sacrificial material layer and a back pole plate structure located on the sacrificial material layer are formed on a substrate, and the back pole plate structure comprises a silicon base layer, a supporting layer and a supporting isolation layer from bottom to top; the corresponding back polar plate structure above the working area comprises a plurality of holes; forming a first opening exposing the sacrificial material layer in the working area to obtain an initial MEMS silicon microphone structure; and at least removing the sacrificial material layer on the working area by etching through the plurality of holes and the first opening so as to form a sacrificial layer, a second opening and a third opening. In conclusion, on one hand, the support isolation layer can provide support for the support layer, so that the reliability of the MEMS silicon microphone structure is improved; and on the other hand, the supporting isolation layer can be used for protecting the surface of the supporting layer from being influenced in the process of etching the sacrificial layer through the hole, so that the performance and the stability of the MEMS silicon microphone structure are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor devices, and more particularly to a MEMS silicon microstructure and its fabrication method. Background Technology

[0002] MEMS silicon microphones, with their advantages of miniaturization, high integration, and low power consumption, are widely used in mobile phones, smart speakers, automotive electronics, and other applications. Structurally, MEMS silicon microphones mainly consist of a diaphragm, a backplate, a sound hole, and a support structure. The backplate comprises a polycrystalline silicon layer and a silicon nitride layer on top of the polycrystalline silicon layer. The sound hole, located in the working area, penetrates both the silicon nitride and polycrystalline silicon layers. This silicon nitride layer provides support for the polycrystalline silicon layer, and its strength directly affects the reliability of the MEMS silicon microphone.

[0003] Please refer to Figure 1 and Figure 2 , Figure 1 It is the initial MEMS silicon microphone structure before the sacrificial layer is released. Figure 2 This is a MEMS silicon microphone structure. During the fabrication of a MEMS silicon microphone, it is necessary to release a sacrificial layer (isolation layer) between the back electrode and the diaphragm corresponding to the working area to form the MEMS silicon microphone structure. Since the sacrificial layer is usually released using hydrofluoric acid gas or buffered oxide etchant, and the silicon nitride layer will be corroded after prolonged contact with hydrofluoric acid gas or buffered oxide etchant, the release of the sacrificial layer can lead to surface roughness and a reduction in the thickness of the silicon nitride layer, resulting in a decrease in the film strength of the silicon nitride layer. Consequently, the back electrode structure collapses and the performance of the formed MEMS silicon microphone structure fails to meet the design value, or even fails. Summary of the Invention

[0004] This invention provides a MEMS silicon microstructure and its fabrication method to improve the reliability of MEMS silicon microstructures.

[0005] According to a first aspect of the present invention, a method for fabricating a MEMS silicon microstructure is provided, comprising: A substrate is provided, the substrate including a working area; A sacrificial material layer, a diaphragm located within the sacrificial material layer, and a back electrode structure located on the sacrificial material layer are formed on the substrate. The back electrode structure includes a silicon substrate, a support layer, and a support isolation layer from bottom to top. A plurality of holes are formed in the back electrode structure corresponding to the working area above the working area. The holes penetrate the support isolation layer, the support layer, and the silicon substrate. A first opening is formed in the working area corresponding to the back side of the substrate to expose the sacrificial material layer in order to obtain an initial MEMS silicon microstructure. The sacrificial material layer on the working area is removed through several holes and the first opening to form a sacrificial layer, a second opening, and a third opening. The second opening communicates with the first opening and exposes at least the lower surface of the diaphragm above the working area. The third opening is located between the back electrode structure and the diaphragm and exposes at least the upper surface of the diaphragm above the working area.

[0006] Optionally, the silicon substrate and the diaphragm are made of polycrystalline silicon or amorphous silicon, the sacrificial material layer is made of silicon oxide, the support layer is made of silicon nitride, and the support isolation layer is made of amorphous carbon.

[0007] Optionally, the method for removing the sacrificial layer, the second opening, and the third opening formed in the sacrificial material layer on the working area includes: within a preset time and a preset concentration, using an etching process to remove the sacrificial material layer on the working area to expose the upper and lower surfaces of the diaphragm above the working area.

[0008] Optionally, an isolation layer is formed on the supporting isolation layer, and the supporting isolation layer and the isolation layer are stacked sequentially on the supporting layer from bottom to top, forming a plurality of holes corresponding to the back electrode structure in the working area.

[0009] Optionally, the isolation layer is a silicon oxide layer, and the method for removing the sacrificial material layer on the working area to form the sacrificial layer, the second opening and the third opening includes: within a preset time and a preset concentration, using an etching process to remove the sacrificial material layer on the working area to expose the lower surface and the upper surface of the diaphragm above the working area, while removing the isolation layer in the supporting isolation layer.

[0010] Optionally, the thickness of the supporting isolation layer ranges from 10 nanometers to 2 micrometers.

[0011] Optionally, the method of forming a sacrificial material layer on the substrate, a diaphragm located within the sacrificial material layer, and a back electrode structure located on the sacrificial material layer includes: A first sacrificial material layer is formed on the upper surface of the substrate; A diaphragm is formed on the first sacrificial material layer, the diaphragm being vertically aligned with the working area, and a portion of the diaphragm being located outside the working area; A second sacrificial material layer is formed on the diaphragm and the exposed first sacrificial material layer, the first sacrificial material layer and the second sacrificial material layer constituting the sacrificial material layer; The silicon substrate is formed on the second sacrificial material layer; The support layer is formed on the silicon substrate and the exposed second sacrificial material layer; The support isolation layer is formed on the support layer; A plurality of holes are formed in the silicon substrate, the support layer and the support isolation layer above the working area to form a back electrode structure.

[0012] Optionally, before forming the first opening exposing the sacrificial material layer in the working area, the method further includes: forming a first through-hole conductive structure and a second through-hole conductive structure, wherein the first through-hole conductive structure penetrates the supporting isolation layer, the supporting layer, and the sacrificial material layer between the supporting layer and the diaphragm, and is electrically connected to the diaphragm; the second through-hole conductive structure penetrates the supporting isolation layer and the supporting layer, and is electrically connected to the silicon substrate; the second through-hole conductive structure and the first through-hole conductive structure are respectively located on opposite sides of the working area.

[0013] Optionally, a method for forming a first opening in the working region to expose the sacrificial material layer to obtain an initial MEMS silicon microstructure includes: The substrate is thinned from its back side; The thinned substrate is etched from the back side of the substrate to form a first opening in the working area that exposes the sacrificial material layer.

[0014] According to a second aspect of the present invention, a MEMS silicon microphone structure is provided, comprising: A substrate, including a first opening through the substrate, the first opening being located within a working area; A sacrificial layer is located on the substrate on both sides of the first opening; A diaphragm is located above the substrate, the diaphragm is suspended above the first opening, and the edge region of the diaphragm is located within the sacrificial layer; The second opening communicates with the first opening and at least exposes the lower surface of the diaphragm above the first opening; A back electrode structure is located on the sacrificial layer, and the back electrode structure includes, from bottom to top, a silicon base layer, a support layer and a support isolation layer. The back electrode structure above the first opening includes a plurality of holes, which penetrate the support isolation layer, the support layer and the silicon base layer. The third opening is located between the backplate structure and the diaphragm and exposes at least the upper surface of the diaphragm above the working area.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: In a method for fabricating a MEMS silicon microphone structure provided by the technical solution of the present invention, a sacrificial material layer, a diaphragm located within the sacrificial material layer, and a back electrode structure located on the sacrificial material layer are formed on a substrate. The back electrode structure includes a silicon substrate, a support layer, and a support isolation layer from bottom to top. A plurality of holes are formed in the back electrode structure corresponding to the working area above the working area, and the holes penetrate the support isolation layer, the support layer, and the silicon substrate. A first opening is formed in the working area on the back side of the substrate to expose the sacrificial material layer, thereby obtaining an initial MEMS silicon microphone structure. The sacrificial material layer on the working area is removed through the plurality of holes and the first opening to form a sacrificial layer, a second opening, and a third opening. The second opening communicates with the first opening and exposes at least the lower surface of the diaphragm above the working area. The third opening is located between the back electrode structure and the diaphragm and exposes at least the upper surface of the diaphragm above the working area. In summary, on the one hand, since the supporting isolation layer can provide support for the supporting layer, the back electrode structure including the supporting isolation layer has greater strength, thereby improving the reliability of the MEMS silicon microphone structure; on the other hand, since the supporting isolation layer is located above the supporting layer, and the supporting isolation layer can be etched through several holes and the first opening to remove at least the sacrificial material layer on the working area without being affected, the supporting isolation layer can be used to protect the surface of the supporting layer during the etching of the sacrificial layer through the holes, thereby improving the performance and stability of the MEMS silicon microphone structure. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the initial MEMS silicon microstructure before the sacrificial layer is released; Figure 2 This is a schematic diagram of a MEMS silicon microstructure. Figures 3-10 This is a cross-sectional structural diagram of each step in the fabrication method of MEMS silicon microstructure provided in the embodiments of the present invention.

[0017] Figure label: 10-Substrate; 20 - Sacrificial material layer; 21-Sacrificial Layer; 201 - First sacrificial material layer; 202 - Second sacrificial material layer; 30-Silicon substrate; 40 - Support layer; 50 - Supporting isolation layer; 61 - First through-hole conductive structure; 62 - Second through-hole conductive structure; 70 - Diaphragm; 80 - Isolation layer; 90-hole; wr - Work area; 91 - First opening; 92 - Second opening; 93 - Third opening. Detailed Implementation

[0018] As described in the background section, the solution used when releasing the sacrificial layer can reduce the strength of the silicon nitride layer, which in turn can cause the back electrode structure to collapse and the performance of the formed MEMS structure to fail to meet the design value or even fail.

[0019] In view of this, the present invention creatively proposes a method for fabricating a MEMS silicon microstructure, comprising: A substrate is provided, the substrate including a working area; A sacrificial material layer, a diaphragm located within the sacrificial material layer, and a back electrode structure located on the sacrificial material layer are formed on the substrate. The back electrode structure includes a silicon substrate, a support layer, and a support isolation layer from bottom to top. A plurality of holes are formed in the back electrode structure corresponding to the working area above the working area. The holes penetrate the support isolation layer, the support layer, and the silicon substrate. A first opening is formed in the working area corresponding to the back side of the substrate to expose the sacrificial material layer in order to obtain an initial MEMS silicon microstructure. The sacrificial material layer on the working area is removed through several holes and the first opening to form a sacrificial layer, a second opening, and a third opening. The second opening communicates with the first opening and exposes at least the lower surface of the diaphragm above the working area. The third opening is located between the back electrode structure and the diaphragm and exposes at least the upper surface of the diaphragm above the working area.

[0020] On the one hand, since the supporting isolation layer can provide support for the supporting layer, the back electrode structure including the supporting isolation layer has greater strength, thereby improving the reliability of the MEMS silicon microphone structure. On the other hand, since the supporting isolation layer is located above the supporting layer, and the supporting isolation layer can be etched through several holes and the first opening to remove at least the sacrificial material layer on the working area without being affected, the supporting isolation layer can be used to protect the surface of the supporting layer during the etching of the sacrificial layer through the holes, thereby improving the performance and stability of the MEMS silicon microphone structure.

[0021] The embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the present invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0022] Please refer to Figures 3-10 This invention provides a method for fabricating a MEMS silicon microstructure, the method comprising: Please refer to Figure 3 A substrate 10 is provided, the substrate 10 including a working region wr.

[0023] In this embodiment, substrate 10 may be a silicon substrate.

[0024] A first sacrificial material layer 201 is formed on the upper surface of the substrate 10. A diaphragm 70 is formed on the first sacrificial material layer 201. The diaphragm 70 corresponds vertically to the working area wr, and part of the diaphragm 70 is located outside the working area wr. The area of ​​the diaphragm 70 is larger than the area of ​​the working area wr.

[0025] As one implementation, the method for forming the diaphragm 70 includes: depositing a diaphragm material layer on the sacrificial material layer 20; spin-coating a photoresist layer on the diaphragm material layer; exposing and developing the photoresist layer using a photomask to form a patterned photoresist layer; and etching the diaphragm material layer using the patterned photoresist layer as a mask, with the etching stopping at the surface of the sacrificial layer 21 to form the diaphragm 70.

[0026] Of course, in actual operation, after the diaphragm 70 is formed, the removal of the remaining patterned photoresist layer is also included.

[0027] Furthermore, it should be understood that the above example uses photoresist as the material of the patterned mask layer. In practical applications, the patterned mask layer can also be made of other materials and can be formed in other ways. This invention is not limited thereto.

[0028] Please refer to Figure 4 A second sacrificial material layer 202 is formed on the surface of the diaphragm 70 and the exposed first sacrificial material layer 201, and the first sacrificial material layer 201 and the second sacrificial material layer 202 constitute the sacrificial material layer 20. A silicon substrate 30 is formed on the second sacrificial material layer 202, the silicon substrate 30 being at least above the working area wr, and the area of ​​the silicon substrate 30 being larger than the area of ​​the working area wr, and one side of the silicon substrate 30 exposing a portion of the diaphragm 70 in the vertical direction. Furthermore, the method for forming the silicon substrate 30 is the same as the method for forming the diaphragm 70 described above, and therefore will not be repeated here.

[0029] Please refer to Figure 5 A support layer 40 is formed on the silicon substrate 30; a support isolation layer 50 is formed on the support layer 40.

[0030] In one specific implementation, the silicon substrate 30 and the diaphragm 70 are made of polycrystalline silicon or amorphous silicon, the sacrificial material layer 20 is silicon oxide, and the support layer 40 is made of silicon nitride. The support isolation layer 50 is an amorphous carbon layer with a thickness ranging from 10 nanometers to 2 micrometers. The thickness of the silicon substrate 30 ranges from 100 nanometers to 800 nanometers, and the thickness of the support layer 40 ranges from 200 nanometers to 2 micrometers. The thickness of the back electrode structure is positively correlated with the strength of the back electrode.

[0031] The beneficial effects of forming an amorphous carbon layer on the support layer 40 include: First, due to the stable performance of the amorphous carbon layer, its deposition on the surface of the silicon nitride layer (i.e., the support layer 40) can effectively improve the strength of the back electrode structure and enhance the reliability of the MEMS silicon microphone structure. Second, because amorphous carbon is resistant to chemical corrosion, it can prevent the corrosive solution from contacting the upper surface of the support layer 40 when the sacrificial material layer 20 is subsequently released, thereby preventing the silicon nitride layer (i.e., the support layer 40) from being corroded, further enhancing the strength of the back electrode structure and further improving the reliability of the MEMS silicon microphone structure. Third, because the stress of the amorphous carbon layer is easy to adjust, the stress of the amorphous carbon layer can be adjusted by adjusting process parameters such as the process temperature, gas flow rate, process pressure, or deposition power to make it compatible with the performance of the MEMS silicon microphone structure.

[0032] As an example, the method for forming the supporting isolation layer 50 can be chemical vapor deposition or physical vapor deposition.

[0033] Please refer to Figure 6 An isolation layer 80 is formed on the support isolation layer 50. The support isolation layer 50 and the isolation layer 80 are stacked sequentially on the support layer 40 from bottom to top. The thickness of the isolation layer 80 is 10 nanometers to 2 micrometers.

[0034] Specifically, forming an isolation layer 80 on the support isolation layer 50 can improve the photolithography accuracy of subsequent formation of the holes 90, the first through-hole conductive structure 61, and the second through-hole conductive structure 62, thereby improving the reliability of the MEMS silicon microphone structure. When the support isolation layer 50 is an amorphous carbon layer, on the one hand, forming an isolation layer 80 on the amorphous carbon layer is beneficial to improving the adhesion of the photoresist, thereby reducing the problems of photoresist detachment and defects in the pattern on the photoresist due to weak adhesion, thus improving the reliability of the formed MEMS silicon microphone structure; on the other hand, oxygen-containing gas is usually required when etching the amorphous carbon layer to form holes, but such oxygen-containing gas usually has a high etching rate for photoresist. Therefore, forming an isolation layer 80 on the amorphous carbon layer can reduce the loss of photoresist during the etching process, further improving the photolithography accuracy.

[0035] As an example, the material of the insulating layer 80 is silicon oxide, and its thickness ranges from 10 nanometers to 2 micrometers.

[0036] Please refer to Figure 7 A first through-hole conductive structure 61 and a second through-hole conductive structure 62 are formed. The first through-hole conductive structure 61 penetrates the supporting isolation layer 50, the supporting layer 40, and the sacrificial material layer 20 between the supporting layer 40 and the diaphragm 70, and is electrically connected to the diaphragm 70. The second through-hole conductive structure 62 penetrates the supporting isolation layer 50 and the supporting layer 40, and is electrically connected to the silicon substrate 30. The second through-hole conductive structure 62 and the first through-hole conductive structure 61 are located on opposite sides of the working area wr. The sacrificial material layer 20 between the supporting layer 40 and the diaphragm 70 is the second sacrificial material layer 202.

[0037] In this embodiment, please refer to Figure 7 The method for forming the first via conductive structure 61 and the second via conductive structure 62 includes: forming a patterned mask layer on an isolation layer 80; using the patterned mask layer as a mask, etching the isolation layer 80, the supporting isolation layer 50, the supporting layer 40, and the second sacrificial layer 21 to form a first groove (not shown in the figure), the bottom of the first groove exposing the diaphragm 70; and etching the isolation layer 80, the supporting isolation layer 50, and the supporting layer 40 to form a second groove (not shown in the figure), the bottom of the second groove exposing the silicon substrate 30; and depositing metal material in the first groove and the second groove to correspondingly form the first via conductive structure 61 and the second via conductive structure 62.

[0038] As an example, the metal material may be gold, copper, titanium or aluminum, etc., and the metal material also covers at least the support isolation layer 50 around the first and second grooves for electrical connection with external devices.

[0039] Please refer to Figure 8A plurality of holes 90 are formed in the silicon substrate 30, support layer 40, support isolation layer 50, and isolation layer 80 above the working area wr to form a back electrode structure. The holes 90 penetrate the isolation layer 80, support isolation layer 50, support layer 40, and silicon substrate 30, and the bottom of the holes 90 exposes a second sacrificial layer 21. The back electrode structure consists only of the silicon substrate 30, support layer 40, and support isolation layer 50.

[0040] In this embodiment, the method for forming the hole 90, the first groove, and the second groove is the same as the method for forming the diaphragm 70 described above, and therefore will not be repeated here.

[0041] It should be noted that the present invention does not limit the order in which the hole 90, the first through-hole conductive structure 61, and the second through-hole conductive structure 62 are formed. Alternatively, the first through-hole conductive structure 61 and the second through-hole conductive structure 62 may be formed after the hole 90 is formed, or the first groove and the second groove corresponding to the hole 90, the first through-hole conductive structure 61, and the second through-hole conductive structure 62 may be formed simultaneously before the first through-hole conductive structure 61 and the second through-hole conductive structure 62 are formed.

[0042] Please refer to Figure 9 A first opening 91 is formed in the working region wr to expose the sacrificial material layer 20 in order to obtain the initial MEMS silicon microstructure.

[0043] In this embodiment, the method of forming a first opening 91 in the working region wr to expose the sacrificial material layer 20 to obtain an initial MEMS silicon microstructure includes: thinning the substrate 10 from the back side of the substrate 10; and etching the thinned substrate 10 from the back side of the substrate 10 to form a first opening 91 in the working region wr to expose the sacrificial material layer 20.

[0044] As an example, the thickness of the thinned substrate 10 ranges from 30 micrometers to 500 micrometers, and the thickness of the thinned substrate 10 can affect the volume of the device after packaging, with the thickness being positively correlated with the volume of the device after packaging.

[0045] Please refer to Figure 10 The sacrificial material layer 20 on the working area wr is removed through several holes 90 and a first opening 91 to form a sacrificial layer 21, a second opening 92, and a third opening 93. The second opening 92 communicates with the first opening 91 and exposes at least the lower surface of the diaphragm 70 above the working area wr. The third opening 93 is located between the back electrode structure and the diaphragm 70 and exposes at least the upper surface of the diaphragm 70 above the working area wr. The isolation layer 80 is removed simultaneously with the removal of the sacrificial material layer 20 on the working area wr.

[0046] Specifically, the method for removing the sacrificial layer 21, the second opening 92, and the third opening 93 formed in the sacrificial material layer 20 on the working area wr includes: within a preset time and preset concentration, using an etching process to remove the sacrificial material layer 20 on the working area wr to expose the upper and lower surfaces of the diaphragm 70 above the working area wr, while simultaneously removing the isolation layer 80. The degree of etching of the sacrificial material layer, i.e., the size of the formed second opening 92 and third opening 93, can be controlled by setting the preset time and preset concentration. This avoids electrical failure and diaphragm collapse caused by excessively large second openings 92 or third openings 93, and also avoids damage to the sidewalls of the support layer 40 in the back electrode structure holes 90, which could lead to back electrode structure collapse.

[0047] In one specific embodiment, the method for forming the sacrificial layer 21, the second opening 92, and the third opening 93 includes: immersing the initial MEMS silicon microstructure in an etching solution within a preset time and a preset concentration to remove the sacrificial material layer 20 on the working area wr, thereby forming the sacrificial layer 21, the second opening 92, and the third opening 93. The etching solution is a hydrofluoric acid solution or a buffered oxide etchant. Preferably, the etching solution is a hydrofluoric acid solution with a preset concentration of 15-30% and a preset time of 20 to 40 minutes.

[0048] When the etching concentration is too high or the etching time is too long, excessive etching of the second opening 92 and the third opening 93 can lead to diaphragm collapse and increased damage to the sidewalls of the support layer 40 in the back electrode structure hole 90. When the etching concentration is too low or the etching time is too short, the sacrificial material layer 20 on the upper and lower surfaces of the diaphragm 70 in the working area wr cannot be guaranteed to be released, thus affecting the performance of the MEMS silicon microphone. However, when the etching solution is a 15-30% hydrofluoric acid solution and the preset time is 20 to 40 minutes, the sacrificial material layer 20 on the upper and lower surfaces of the diaphragm 70 in the working area wr can be released more effectively with minimal damage to the sidewalls of the support layer 40 in the back electrode structure hole 90, which is beneficial to improving the reliability of the MEMS silicon microphone. Preferably, the etching solution is a 20% hydrofluoric acid solution and the preset time is 20 to 40 minutes to achieve the best etching effect. The specific preset time depends on the design size of the MEMS silicon microphone structure and is not specifically limited here.

[0049] In another specific embodiment, the method for forming the sacrificial layer 21, the second opening 92 and the third opening 93 includes: placing the initial MEMS silicon microstructure in a chamber filled with corrosive gas within a preset time to remove the sacrificial material layer 20 on the working area wr, thereby forming the sacrificial layer 21, the second opening 92 and the third opening 93, wherein the corrosive gas is hydrofluoric acid gas.

[0050] In summary, in the method for fabricating a MEMS silicon microphone structure provided in this embodiment of the invention, a sacrificial material layer 20, a diaphragm 70 located within the sacrificial material layer 20, and a back electrode structure located on the sacrificial material layer 20 are formed on a substrate 10. The back electrode structure, from bottom to top, includes a silicon substrate 30, a support layer 40, and a support isolation layer 50. The back electrode structure above the working area wr includes a plurality of holes 90, which penetrate the support isolation layer 50, the support layer 40, and the silicon substrate 30. The working area wr on the back side of the substrate... A first opening 91 is formed to expose the sacrificial material layer 20, thus obtaining an initial MEMS silicon microphone structure. The sacrificial material layer 20 on the working area wr is removed through several holes 90 and the first opening 91 to form a sacrificial layer 21, a second opening 92, and a third opening 93. The second opening 92 communicates with the first opening 91 and exposes at least the lower surface of the diaphragm 70 above the working area wr. The third opening 93 is located between the back electrode structure and the diaphragm 70 and exposes at least the upper surface of the diaphragm 70 above the working area wr. On one hand, because the supporting isolation layer 50 provides support for the supporting layer 40, the back electrode structure including the supporting isolation layer 50 has greater strength, thereby improving the reliability of the MEMS silicon microphone structure. On the other hand, because the supporting isolation layer 50 is located above the supporting layer 40, it can protect the surface of the supporting layer 40 from damage during the etching of the sacrificial material layer 20 through the holes 90, thereby improving the performance and stability of the MEMS silicon microphone structure. Furthermore, setting a preset time and preset concentration can more effectively ensure that the sacrificial material layer 20 on the upper and lower surfaces of the diaphragm 70 in the working area wr is released smoothly and minimize the loss to the sidewall of the support layer 40 in the hole 90 in the back electrode structure, thereby further improving the reliability of the MEMS silicon microphone.

[0051] Please refer to Figure 9 The present invention also provides a MEMS silicon microphone structure, including: a substrate 10, a sacrificial layer 21, a diaphragm 70, a second opening 92, a back electrode structure, and a third opening 93.

[0052] The substrate 10 includes a first opening 91 located within the working region wr and extending through the substrate 10.

[0053] The sacrificial layer 21 is located on the substrate 10 on both sides of the first opening 91, and the sacrificial layer 21 includes a first sacrificial layer 21 and a second sacrificial layer 21. The first sacrificial layer 21 is located between the substrate 10 and the diaphragm 70, and the second sacrificial layer 21 is located on the upper surface and side surface of the diaphragm 70.

[0054] The diaphragm 70 is located above the substrate 10 and is suspended above the first opening 91. The edge region of the diaphragm 70 is located within the sacrificial layer 21.

[0055] The second opening 92 communicates with the first opening 91 and exposes at least the lower surface of the diaphragm 70 above the first opening 91.

[0056] The back electrode structure is located on the sacrificial layer 21, and the back electrode structure includes, from bottom to top, a silicon base layer 30, a support layer 40 and a support isolation layer 50. The back electrode structure above the first opening 91 includes a number of holes 90, which penetrate the support isolation layer 50, the support layer 40 and the silicon base layer 30.

[0057] The third opening 93 is located between the back electrode structure and the diaphragm 70 and exposes at least the upper surface of the diaphragm 70 above the working area wr.

[0058] The MEMS silicon microphone structure provided by the present invention includes a supporting isolation layer 50 in its back electrode structure, which improves the strength of the back electrode structure and further improves the reliability of the MEMS silicon microphone structure, thereby solving the problem of low reliability of MEMS silicon microphone structure caused by back electrode structure collapse in the prior art.

[0059] The materials, formation process, working principle, specific implementation method and beneficial effects of the MEMS silicon microphone structure in the embodiments of the present invention can be found in the MEMS silicon microphone fabrication method in the embodiments of the present invention, and will not be repeated here.

[0060] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A method for manufacturing a MEMS silicon microphone structure, characterized by, The application relates to a method for manufacturing a MEMS silicon microphone. The application comprises the following steps: providing a substrate, wherein the substrate comprises a working area; forming a sacrificial material layer, a diaphragm in the sacrificial material layer and a back plate structure on the sacrificial material layer on the substrate, wherein the back plate structure comprises, from bottom to top, a silicon base layer, a support layer and a support isolation layer, a plurality of holes are formed in the back plate structure corresponding to the working area, and the holes penetrate through the support isolation layer, the support layer and the silicon base layer; forming a first opening exposing the sacrificial material layer on the substrate back surface corresponding to the working area to obtain an initial MEMS silicon microphone structure; 2. The method of claim 1, wherein the MEMS silicon microphone structure is prepared by the steps of: removing the sacrificial material layer on the working area through the holes and the first opening to form a sacrificial layer, a second opening and a third opening, wherein the second opening is communicated with the first opening and exposes at least a lower surface of the diaphragm above the working area, and the third opening is located between the back plate structure and the diaphragm and exposes at least an upper surface of the diaphragm above the working area. ​ 3. The method of claim 2, wherein the MEMS silicon microphone structure is prepared by the steps of: The material of the silicon base layer and the diaphragm is polycrystalline silicon or amorphous silicon, the material of the sacrificial material layer is silicon oxide, the material of the support layer is silicon nitride, and the support isolation layer is an amorphous carbon layer. ​ 4. The method of claim 2, wherein the MEMS silicon microphone structure is prepared by the steps of: The method for removing the sacrificial material layer on the working area to form the sacrificial layer, the second opening and the third opening comprises the following steps: adopting an etching process to remove the sacrificial material layer on the working area within a preset time and a preset concentration to expose the upper surface and the lower surface of the diaphragm above the working area. ​ 5. The method of claim 4, wherein the MEMS silicon microphone structure is prepared by the steps of: The support isolation layer and the isolation layer are sequentially stacked on the support layer from bottom to top, and a plurality of holes corresponding to the back plate structure are formed on the working area. ​ 6. The method of claim 2 to 5, wherein, The method for removing the sacrificial material layer on the working area to form the sacrificial layer, the second opening and the third opening comprises the following steps: adopting an etching process to remove the sacrificial material layer on the working area within a preset time and a preset concentration to expose the lower surface and the upper surface of the diaphragm above the working area, and simultaneously remove the isolation layer.

7. The method for fabricating a MEMS silicon microstructure according to claim 1, characterized in that, The thickness of the support isolation layer ranges from 10 nanometers to 2 micrometers. The method for forming the sacrificial material layer, the diaphragm in the sacrificial material layer and the back plate structure on the sacrificial material layer on the substrate comprises the following steps: forming a first sacrificial material layer on the upper surface of the substrate; forming the diaphragm on the first sacrificial material layer, wherein the diaphragm corresponds to the working area in a vertical direction, and the diaphragm is partially located outside the working area; forming a second sacrificial material layer on the diaphragm and the exposed first sacrificial material layer, wherein the first sacrificial material layer and the second sacrificial material layer constitute the sacrificial material layer; forming the silicon base layer on the second sacrificial material layer; forming the support layer on the silicon base layer and the exposed second sacrificial material layer; forming the support isolation layer on the support layer; forming a plurality of holes in the silicon base layer, the support layer and the support isolation layer corresponding to the working area to form the back plate structure.

8. The method of claim 1, wherein the MEMS silicon microphone structure is prepared by the steps of: Before forming the first opening in the working area to expose the sacrificial material layer, the method further comprises: forming a first via conductive structure and a second via conductive structure, the first via conductive structure penetrating through the support isolation layer, the support layer and the sacrificial material layer between the support layer and the diaphragm, and electrically connected with the diaphragm, the second via conductive structure penetrating through the support isolation layer and the support layer, and electrically connected with the silicon base layer, the second via conductive structure and the first via conductive structure are respectively located on opposite sides of the working area. ​ 9. The method for fabricating a MEMS silicon microstructure according to claim 1, characterized in that, The method for forming the first opening in the working area to expose the sacrificial material layer to obtain an initial MEMS silicon microphone structure comprises: Thinning the substrate from the back surface of the substrate; Etching the thinned substrate from the back surface of the substrate to form a first opening in the working area to expose the sacrificial material layer.

10. A MEMS silicon microphone structure, characterized by Comprise: A substrate comprising a first opening penetrating through the substrate, the first opening being located in a working area; A sacrificial layer located on the substrate on both sides of the first opening; A diaphragm located above the substrate, the diaphragm being suspended above the first opening, the edge region of the diaphragm being located in the sacrificial layer; A second opening communicating with the first opening and exposing at least the lower surface of the diaphragm above the first opening; A back plate structure located on the sacrificial layer, and the back plate structure comprises a silicon base layer, a support layer and a support isolation layer from bottom to top, the corresponding back plate structure above the first opening comprises a plurality of holes penetrating through the support isolation layer, the support layer and the silicon base layer; A third opening located between the back plate structure and the diaphragm and exposing at least the upper surface of the diaphragm above the working area.

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