Micro-electro-mechanical microphone and manufacturing method thereof

Abstract

The invention discloses a micro-electro-mechanical microphone and a manufacturing method thereof. The MEMS microphone includes a substrate, a diaphragm, and a back plate. The substrate has a cavity. The diaphragm is disposed on the substrate and spans the cavity. The back plate is arranged above the vibrating diaphragm and is separated from the vibrating diaphragm through an air gap. The diaphragm has a corrugated structure. And the back plate is provided with a part which corresponds to the corrugated structure and is positioned right above the corrugated structure. The height difference of the part is smaller than or equal to 20% of the height difference of the corrugated structure.

Description

TECHNICAL FIELD

[0001] The present application relates to a micro-electro-mechanical systems (MEMS) microphone and a manufacturing method thereof. In particular, the present application relates to a micro-electro-mechanical systems microphone having a corrugated structure in a diaphragm and a manufacturing method thereof. BACKGROUND

[0002] A micro-electro-mechanical systems microphone is a small microphone device manufactured by using semiconductor manufacturing processes. The size of the device is in the range of several micrometers to several millimeters. Generally, the micro-electro-mechanical systems microphone includes a diaphragm and a back plate. The diaphragm is very thin so that it can vibrate in response to sound waves. The back plate is disposed opposite to the diaphragm. When the diaphragm vibrates, the distance between the diaphragm and the back plate changes, and thus the capacitance between the diaphragm and the back plate changes. As a result, the sound waves can be converted into an electrical signal. A corrugated structure can be formed in the diaphragm to improve the sensitivity of the device. However, due to the manufacturing processes, the height difference of the corrugated structure can be transferred to the subsequently formed back plate and form a sharp profile on the back plate. In this way, the back plate can have a weak point of stress concentration, which can cause damage to the device. SUMMARY

[0003] The present application aims to solve or at least alleviate the above problems.

[0004] In one embodiment of the present application, a micro-electro-mechanical systems microphone is provided. The micro-electro-mechanical systems microphone includes a substrate, a diaphragm, and a back plate. The substrate has a cavity. The diaphragm is disposed on the substrate and spans the cavity. The back plate is disposed above the diaphragm and separated from the diaphragm by an air gap. The diaphragm has a corrugated structure. The back plate has a portion corresponding to the corrugated structure and directly above the corrugated structure. The portion has a height difference less than or equal to 20% of a height difference of the corrugated structure.

[0005] In another embodiment of the present application, a manufacturing method of a micro-electro-mechanical systems microphone is provided. The manufacturing method includes the following steps. First, a diaphragm is formed on a substrate. The diaphragm has a corrugated structure. Then, a stop layer is formed on the diaphragm. The stop layer has an opening exposing the corrugated structure. A temporary filling material is filled into the corrugated structure through the opening of the stop layer. A back plate is formed above the temporary filling material and the diaphragm.

[0006] According to the present application, a filling manufacturing process is performed on the corrugated structure of the diaphragm before the back plate is formed. In this way, a micro-electro-mechanical systems microphone having a corrugated structure in the diaphragm but substantially no stress concentration point caused by manufacturing process transfer in the back plate can be provided.

[0007] For a better understanding of the present application and to show how the same can be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which: Attached Figure Description

[0008] Figure 1 This is a schematic diagram of the microelectromechanical microphone of the present invention;

[0009] Figure 2 This is a schematic diagram of another microelectromechanical microphone of the present invention;

[0010] Figures 3A-3B This is a schematic diagram showing details of the microelectromechanical microphone of the present invention;

[0011] Figures 4A-4P This is a schematic diagram of the various stages of the manufacturing method of the microelectromechanical microphone of the present invention.

[0012] Symbol Explanation

[0013] 100,100': Microelectromechanical microphone

[0014] 110:Substrate

[0015] 112: Notch

[0016] 120, 120': Diaphragm

[0017] 120A: Floor

[0018] 122,122': Corrugated structure

[0019] 124: Hole

[0020] 130: Backplate

[0021] 132: Part

[0022] 134: Bump

[0023] 136: Sound hole

[0024] 140: Dielectric layer

[0025] 142: Dielectric layer

[0026] 144: Dielectric layer

[0027] 146: Dielectric layer

[0028] 148: Protective layer

[0029] 150: Circuit Components

[0030] 152: Contact element

[0031] 154: Connecting pad

[0032] 202: Stopping Layer

[0033] 204: First Mask

[0034] 206: second mask

[0035] 208: temporary filling material

[0036] 210: sacrificial layer

[0037] 212: notch

[0038] 214: hole

[0039] C: cavity

[0040] h b : step height

[0041] h m : step height

[0042] G: air gap

[0043] O: opening DETAILED DESCRIPTION

[0044] Various embodiments will be described in greater detail below, with reference to the accompanying drawings. The description and drawings are illustrative of the embodiments and are not intended to limit the embodiments. Like reference symbols in the drawings and description indicate like elements. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an overly literal or overly formal sense unless expressly so defined herein.

[0045] Reference will now be made to Figure 1 , which shows a microelectromechanical microphone 100 according to the present disclosure. The microelectromechanical microphone 100 comprises a substrate 110, a diaphragm 120, and a backplate 130. The substrate 110 has a cavity C. The diaphragm 120 is disposed on the substrate 110 and spans the cavity C. The backplate 130 is disposed above the diaphragm 120 and is separated from the diaphragm 120 by an air gap G. The diaphragm 120 has a corrugated structure 122. The backplate 130 has a portion 132 corresponding to the corrugated structure 122 and directly above the corrugated structure 122. The step height of the portion 132 is less than or equal to 20% of the step height of the corrugated structure 122.

[0046] In particular, the material of the substrate 110 can be, for example, silicon. However, the present disclosure is not limited thereto. The cavity C extends through the substrate 110.

[0047] According to some embodiments, the microelectromechanical microphone 100 can further comprise a dielectric layer 140. The dielectric layer 140 is disposed on the substrate 110. The material of the dielectric layer 140 can be, for example, oxide. The thickness of the dielectric layer 140 can be, for example, 1 pm. To However, the present application is not limited thereto. In the case where the dielectric layer 140 is included, the cavity C penetrates the dielectric layer 140 and the substrate 110.

[0048] In the case where the dielectric layer 140 is included, the diaphragm 120 is disposed on the dielectric layer 140. The material of the diaphragm 120 can be, for example, polysilicon. The thickness of the diaphragm 120 can be, for example, To However, the present application is not limited thereto. The corrugated structure 122 of the diaphragm 120 is advantageous in improving the sensitivity of the microelectromechanical microphone 100. In the case where the dielectric layer 140 is included, the corrugated structure 122 of the diaphragm 120 penetrates the dielectric layer 140. Figure 1 In the microelectromechanical microphone 100 shown, the diaphragm 120 includes one corrugated structure 122. However, it is understood that the diaphragm 120 can include two or more corrugated structures. For example, in the case where the dielectric layer 140 is included, the diaphragm 120 can include two corrugated structures 122. Figure 2 In the microelectromechanical microphone 100' shown, the diaphragm 120' includes two corrugated structures 122'.

[0049] According to some embodiments, the microelectromechanical microphone 100 can further include a dielectric layer 142. The dielectric layer 142 is disposed on the portion of the diaphragm 120 not exposed to the air gap G and on the dielectric layer 140. The material of the dielectric layer 142 can be, for example, tetraethoxysilane (TEOS). The thickness of the dielectric layer 142 can be, for example, To However, the present application is not limited thereto.

[0050] According to some embodiments, the microelectromechanical microphone 100 can further include a dielectric layer 144 supporting the backplate 130 above the air gap G. The dielectric layer 144 is disposed on the dielectric layer 142. The material of the dielectric layer 144 can be, for example, oxide. The thickness of the dielectric layer 144 can be, for example, To However, the present application is not limited thereto. The air gap G can be understood as virtually a hollowed portion of the dielectric layer 144.

[0051] The backplate 130 is supported on the dielectric layer 144. The material of the backplate 130 can be, for example, polysilicon. The thickness of the backplate 130 can be, for example, To However, the present application is not limited thereto. The backplate 130 can include a plurality of dimples 134. The dimples 134 face the diaphragm 120. The backplate 130 can include a plurality of sound holes 136. The sound holes 136 penetrate the backplate 130. According to some embodiments, the microelectromechanical microphone 100 can further include a dielectric layer 146 on the underside of the backplate 130. The material of the dielectric layer 146 can be, for example, silicon nitride. The thickness of the dielectric layer 146 can be, for example, To However, the present application is not limited thereto. According to some embodiments, the micro-electro-mechanical microphone 100 can further comprise a protective layer 148 on the upper side of the back plate 130. The material of the protective layer 148 can be, for example, silicon nitride. The thickness of the protective layer 148 can be, for example, 1000 nm to 2000 nm. to However, the present application is not limited thereto.

[0052] Please refer to Figure 3A which is a magnified view of the corrugation structure 122 of the diaphragm 120 and the corresponding portion 132 of the back plate 130. According to some embodiments, as shown in Figure 3A , the height difference h b of the portion 132 can be the vertical distance between the highest point and the lowest point of the upper surface of the back plate 130, and the height difference h m of the corrugation structure 122 can be the vertical distance between the highest point and the lowest point of the upper surface of the diaphragm 120. The back plate 130 can be substantially flat at the portion 132. That is, the height difference h b of the portion 132 is zero. The highest point of the corrugation structure 122 can be located at the flat portion of the diaphragm 120, and the lowest point can be located at the deepest point of the corrugation structure 122.

[0053] According to other embodiments, as shown in Figure 3B , the height difference h b of the portion 132 can be the vertical distance between the highest point and the lowest point of the lower surface of the back plate 130, and the height difference h m of the corrugation structure 122 can be the vertical distance between the highest point and the lowest point of the lower surface of the diaphragm 120. The back plate 130 can be substantially flat at the portion 132. That is, the height difference h b of the portion 132 is zero. The highest point of the corrugation structure 122 can be located at the flat portion of the diaphragm 120, and the lowest point can be located at the deepest point of the corrugation structure 122.

[0054] According to some embodiments, the micro-electro-mechanical microphone 100 can further comprise circuit elements 150. The circuit elements 150 for the micro-electro-mechanical microphone 100 include, for example but not limited to, conductive contacts 152 and pads 154. The material of the contacts 152 can be, for example, metal. The thickness of the contacts 152 can be, for example, 100 nm to 1000 nm. to However, the present application is not limited thereto. The pads 154 can include, for example, polysilicon and metal thereon. The thickness of the polysilicon can be, for example, 100 nm to 1000 nm. to The thickness of the metal can be, for example, 100 nm to 1000 nm. to However, the present application is not limited thereto.

[0055] The present application now describes a method of manufacturing a microelectromechanical microphone as described above. The method of manufacturing a microelectromechanical microphone according to the present application comprises the following steps. First, a diaphragm is formed on a substrate. The diaphragm has a corrugated structure. Next, a stop layer is formed on the diaphragm. The stop layer has openings exposing the corrugated structure. A temporary filling material is filled through the openings of the stop layer into the corrugated structure. A backplate is formed over the temporary filling material and the diaphragm.

[0056] For further details, reference is made to Figures 4A-4P which shows various stages of a method of manufacturing a microelectromechanical microphone 100.

[0057] As shown in Figure 4A , first a substrate 110 can be provided. The substrate 110 can be formed of silicon. However, the present application is not limited thereto. On the substrate 110, a recess 112 is formed at a position corresponding to a corrugated structure 122 to be formed of a diaphragm 120.

[0058] Next, a dielectric layer 140 can be formed conformally on the substrate 110. The dielectric layer 140 can be formed of oxide. The thickness of the dielectric layer 140 can be in the range of 0.1 to 1 micrometer. to In some embodiments, the dielectric layer 140 can be formed not only on the upper surface of the substrate 110, but also on the lower surface of the substrate 110. However, the present application is not limited thereto.

[0059] As shown in Figure 4B , the diaphragm 120 is formed on the substrate 110, in particular conformally on the dielectric layer 140. The diaphragm 120 has the corrugated structure 122. The diaphragm 120 can be formed of polysilicon. The thickness of the diaphragm 120 can be in the range of 0.1 to 1 micrometer. to In some embodiments, the material of the diaphragm 120 is also provided on the dielectric layer 140 on the lower side of the substrate 110, forming a layer 120A. However, the present application is not limited thereto.

[0060] One or more holes 124 are formed through the diaphragm 120, as shown in Figure 4C . Next, a dielectric layer 142 can be formed on the diaphragm 120. The material of the dielectric layer 142 seals the holes 124. The dielectric layer 142 can be formed of tetraethoxysilane (TEOS) by a low pressure process. The thickness of the dielectric layer 142 can be in the range of 0.1 to 1 micrometer. to However, the present application is not limited thereto.

[0061] Then, a stop layer 202 is formed on the diaphragm 120, in particular on the dielectric layer 142. The stop layer 202 has openings O exposing the corrugated structure 122.

[0062] Specifically, such as Figure 4D As shown, a stop layer material is formed on the diaphragm 120, particularly on the dielectric layer 142. The stop layer material is, for example, silicon nitride. However, the invention is not limited thereto.

[0063] like Figure 4E As shown, a first mask 204 is formed on the stop layer material. The first mask 204 may be formed of an oxide. However, the invention is not limited thereto. A second mask 206 is formed on the first mask 204. The second mask 206 may be formed of a photoresist. However, the invention is not limited thereto. The second mask 206 has openings corresponding to the corrugated structure 122 of the diaphragm 120.

[0064] The first mask 204 is etched using the second mask 206. The second mask 206 is then removed. Next, the stop layer 202 is etched using the first mask 204, such that the stop layer 202 has the opening O exposing the corrugated structure 122. The first mask 204 is then removed, as... Figure 4F As shown.

[0065] Then, temporary filler material 208 is filled into the corrugated structure 122 through the opening O of the stop layer 202. Temporary filler material 208 is, for example, an oxide. However, the invention is not limited thereto.

[0066] Specifically, such as Figure 4G As shown, a temporary filler material 208 is provided on the stop layer 202. The temporary filler material 208 can enter the corrugated structure 122 through the opening O of the stop layer 202.

[0067] Next, as Figure 4H As shown, excess portions of the temporary filler material 208 are removed by utilizing a planarization process for the stop layer 202, such as a chemical mechanical planarization (CMP) process.

[0068] like Figure 4I As shown, remove the stop layer 202. In this step, the temporary filler material 208 at the same height can also be removed.

[0069] Due to the planarization process, after the step of filling with temporary filler material 208, the temporary filler material 208 forms a substantially flat upper surface above the corrugated structure 122. The height difference of the substantially flat upper surface can be less than or equal to 20% of the height difference of the corrugated structure 122, or even zero.

[0070] like Figure 4J As shown, a sacrificial layer 210 is formed on the diaphragm 120. The sacrificial layer 210 can be formed of an oxide. The thickness of the sacrificial layer 210 can be... arrive However, the present invention is not limited thereto.

[0071] like Figure 4K As shown, multiple notches 212 are formed on the sacrificial layer 210 at the positions of the multiple protrusions 134 corresponding to the back plate 130. The notches 212 can be formed by photolithography and / or etching processes. However, the present invention is not limited thereto.

[0072] Then, a backplate 130 is formed over the temporary filler material 208 and the diaphragm 120, particularly on the sacrificial layer 210.

[0073] Specifically, such as Figure 4L As shown, a dielectric layer 146 can be conformally formed on the sacrificial layer 210. The dielectric layer 146 can be formed of silicon nitride. The thickness of the dielectric layer 146 can be... arrive However, the invention is not limited thereto. The backplate 130 is formed on the sacrificial layer 210, particularly on the dielectric layer 146. The backplate 130 has a plurality of bumps 134 located in the notch 212 and a plurality of sound holes 136 passing through the backplate 130. The backplate 130 can be formed of polysilicon. The thickness of the backplate 130 can be... arrive However, the present invention is not limited thereto. Next, a protective layer 148 can be conformally formed on the backplate 130. The protective layer 148 can be formed of silicon nitride. The thickness of the protective layer 148 can be... arrive In some embodiments, a protective layer 148 is also formed on layer 120A on the underside of substrate 110. However, the invention is not limited thereto.

[0074] like Figure 4M As shown, circuit elements 150 for a microelectromechanical microphone 100 can be formed. Circuit elements 150 include, for example, but not limited to, contacts 152 and pads 154. For example, holes can be formed around the backplate 130 through the protective layer 148, sacrificial layer 210, and dielectric layer 142 onto the diaphragm 120, and deposited thereon. arrive A thick metal layer is applied to the sidewalls of the hole to form the contact 152. This can be formed simultaneously around the back plate 130 during the step of forming the back plate 130. arrive A polycrystalline silicon layer, exposed to a protective layer 148, is deposited. arrive A thick metal layer is applied onto the polycrystalline silicon layer to form pad 154. However, the invention is not limited thereto.

[0075] like Figure 4NAs shown, a hole 214 is formed from the sound hole 136 and extends into the sacrificial layer 210. The hole 214 can be formed by photolithography and / or etching processes. However, the present invention is not limited thereto.

[0076] like Figure 4O As shown, substrate 110 is thinned from its underside. In this fabrication process, dielectric layer 140, layer 120, and protective layer 148 on the underside of substrate 110 are also removed. Next, a cavity C is formed in substrate 110. The cavity C can be formed using photolithography and / or etching processes. However, the invention is not limited thereto.

[0077] like Figure 4P As shown, an air gap G is formed between the backplate 130 and the diaphragm 120. Specifically, for example, hydrofluoric acid can be used to remove portions of dielectric layer 140 and dielectric layer 142 between the sacrificial layer 210 and the cavity C, including the portion of dielectric layer 142 located in the aperture 124. Hydrofluoric acid then removes the portion of sacrificial layer 210 between the backplate 130 and the diaphragm 120 through the cavity C and the aperture 124, forming the air gap G. The remaining portion of the sacrificial layer 210 is the dielectric layer 144 as described above.

[0078] In the manufacturing method according to the present invention, before forming the sacrificial layer 210, the corrugated structure 122 is filled with a temporary filler material 208 to smooth the contour of the diaphragm 120. Therefore, it is possible to prevent sharp contours from forming on the backplate due to process transfer. Specifically, the backplate 130 has a portion 132 corresponding to the corrugated structure 122 and located directly above the corrugated structure 122 (shown in...). Figure 1 The height difference of the portion 132 is less than or equal to 20% of the height difference of the corrugated structure 122, or even zero. This prevents or at least reduces device damage caused by stress concentration. Furthermore, since the backplate 130 is not affected by the corrugated structure 122 of the diaphragm 120, the design of the diaphragm 120 can be more flexible.

[0079] While the present invention has been disclosed above by way of embodiments, it is not intended to limit the invention. Those skilled in the art to which this invention pertains can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of this invention should be defined by the appended claims.

Claims

1. A microelectromechanical microphone, comprising: a substrate having a cavity; a diaphragm disposed on the substrate and spanning the cavity; and a backplate disposed above the diaphragm and separated from the diaphragm by an air gap; wherein the diaphragm has a corrugated structure, the backplate has a portion corresponding to and directly above the corrugated structure, and a height difference of the portion is less than or equal to 20% of a height difference of the corrugated structure. The diaphragm includes two or more of the corrugated structures.

2. The microelectromechanical microphone of claim 1, wherein, The backplate includes a plurality of bumps and a plurality of sound holes, the bumps facing the diaphragm.

3. The microelectromechanical microphone of claim 1, wherein, The height difference of the portion is a vertical distance between a highest point and a lowest point of an upper surface of the backplate, and the height difference of the corrugated structure is a vertical distance between a highest point and a lowest point of an upper surface of the diaphragm.

4. The microelectromechanical microphone of claim 1, wherein, The height difference of the portion is a vertical distance between a highest point and a lowest point of a lower surface of the backplate, and the height difference of the corrugated structure is a vertical distance between a highest point and a lowest point of a lower surface of the diaphragm.

5. The microelectromechanical microphone of claim 1, wherein, The height difference of the portion is zero.

6. The microelectromechanical microphone of claim 1, wherein, 7. A method of manufacturing a microelectromechanical microphone, comprising: forming a diaphragm on a substrate, the diaphragm having a corrugated structure; forming a stop layer on the diaphragm, the stop layer having an opening exposing the corrugated structure; filling a temporary fill material through the opening of the stop layer into the corrugated structure; and forming a backplate above the temporary fill material and the diaphragm. Before the step of forming the diaphragm, the method of manufacturing the microelectromechanical microphone further comprises: forming a dielectric layer on the substrate.

8. The method of manufacturing a microelectromechanical microphone according to claim 7, wherein, After the step of forming the diaphragm, the method of manufacturing the microelectromechanical microphone further comprises: forming one or more holes through the diaphragm; and 9. The method of manufacturing a microelectromechanical microphone according to claim 7, wherein, forming a dielectric layer on the diaphragm, wherein a material of the dielectric layer seals the holes. The step of forming the stop layer on the diaphragm comprises: forming a stop layer material on the diaphragm; 10. The method of manufacturing a microelectromechanical microphone according to claim 7, wherein, forming a first mask on the stop layer material; forming a second mask on the first mask, the second mask having an opening corresponding to the corrugated structure of the diaphragm; etching the first mask using the second mask; removing the second mask; etching the stop layer using the first mask such that the stop layer has the opening exposing the corrugated structure; and removing the first mask. The step of filling the temporary fill material comprises: providing the temporary fill material on the stop layer; and 11. The method of manufacturing a microelectromechanical microphone according to claim 7, wherein, removing excess portions of the temporary fill material by a planarization fabrication process using the stop layer. After the step of filling the temporary fill material, the temporary fill material forms a substantially planar upper surface above the corrugated structure. A height difference of the substantially planar upper surface is less than or equal to 20% of a height difference of the corrugated structure.

12. The method of manufacturing a microelectromechanical microphone as claimed in claim 7, wherein, After the step of filling the temporary fill material and before the step of forming the backplate, the method of manufacturing the microelectromechanical microphone further comprises:

13. The method of manufacturing a microelectromechanical microphone according to claim 12, wherein, removing the stop layer.

14. The method of manufacturing a microelectromechanical microphone according to claim 7, wherein, ​ ​ 15. The method of manufacturing a microelectromechanical microphone as claimed in claim 7, wherein, After the step of filling the temporary filling material, and before the step of forming the back plate, the method of manufacturing a microelectromechanical microphone further comprises: forming a sacrificial layer on the diaphragm.

16. The method of manufacturing a microelectromechanical microphone of claim 15, further comprising: forming a plurality of notches on the sacrificial layer at locations corresponding to a plurality of bumps of the back plate.

17. The method of manufacturing a microelectromechanical microphone as claimed in claim 7, wherein, After the step of forming the back plate, the method of manufacturing a microelectromechanical microphone further comprises: forming a circuit element for the microelectromechanical microphone.

18. The method of manufacturing a microelectromechanical microphone as claimed in claim 7, wherein, After the step of forming the back plate, the method of manufacturing a microelectromechanical microphone further comprises: forming a cavity in the substrate; and forming an air gap between the back plate and the diaphragm.

19. The method of manufacturing a microelectromechanical microphone as claimed in claim 7, wherein, The back plate has a portion corresponding to and directly above the corrugated structure, the portion having a height difference less than or equal to 20% of a height difference of the corrugated structure.

20. The method of manufacturing a microelectromechanical microphone according to claim 19, wherein, The height difference of the portion is zero.

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