Micro-electromechanical systems and their manufacturing processes

Abstract

A micro-electromechanical system includes a lower membrane having a plurality of alternately arranged troughs and crests, an upper membrane including a plurality of alternately arranged troughs and crests, and a spacer layer arranged between the lower membrane and the upper membrane. The spacer layer includes a counter electrode wall and a support wall made of nitride, and a conductive element is arranged on the counter electrode wall. A chamber is formed between the lower membrane groove and the top of the upper membrane, the counter electrode walls are suspended in the chamber respectively, the support walls are sandwiched between the crests of the lower membrane and the troughs of the upper membrane, and a space is formed between adjacent support walls. The space between adjacent support walls can be empty or filled with oxide, and the unwanted capacitance between the upper membrane and the lower membrane is significantly reduced.

Description

[Technical field]

[0001] The present invention relates to the field of electroacoustic conversion devices, and in particular to a micro-electromechanical system (MEMS) used in electroacoustic conversion devices and a manufacturing process. [Background technology]

[0002] In current corrugated package MEMS microphones with upper and lower corrugated membranes, there is a spacer layer connecting the upper and lower corrugated membranes. Traditionally, the spacer layer is made of the same material as the counter electrode in the membrane. The spacer layer is usually made of silicon nitride because of its excellent mechanical properties.

[0003] However, silicon nitride has a high dielectric constant of 9.5. In implementations using corrugated encapsulation membranes of conductive materials such as polysilicon, very high plate-to-plate capacitances will be generated between the membranes, which will negatively impact the performance of the microphone.

[0004] Therefore, there is a need to provide an improved micro-electromechanical system that can overcome the above problems. [Summary of the invention]

[0005] The object of the present invention is to overcome the above technical problems and provide a micro-electromechanical system that reduces unnecessary capacitance between diaphragms.

[0006] On the one hand, the process includes:

[0007] Providing a conductive lower film;

[0008] A spacer layer is formed on the lower film, comprising:

[0009] forming a plurality of counter electrode walls and a plurality of support walls on the lower film by using the first material, forming spaces between adjacent walls, and providing conductive elements on the counter electrode walls; and

[0010] filling the space with a second material, the second material having a dielectric constant less than the dielectric constant of the first material;

[0011] providing a conductive upper film overlying the spacer layer; and

[0012] The second material around the counter electrode wall is released so that the portions of the lower and upper films aligned with the counter electrode wall can be displaced relative to the counter electrode wall.

[0013] In some embodiments, the lower film includes a plurality of wave valleys and wave peaks arranged alternately, and provides a conductive lower film, comprising:

[0014] A lower film is provided in which the valleys are filled with the second material.

[0015] In some embodiments, a plurality of counter electrode walls and a plurality of support walls are formed on the lower film, including:

[0016] A plurality of counter electrode walls are formed on the second material filled in the valleys of the lower film, and a plurality of support walls are formed on the peaks of the lower film.

[0017] In some embodiments, the upper film includes a plurality of alternately arranged troughs and peaks; providing a conductive upper film covering the spacer layer, comprising:

[0018] providing a conductive upper film having recesses formed below crests thereof and filled with a second material;

[0019] The wave crests of the upper membrane are aligned with the wave troughs of the lower membrane to form a chamber, in which the counter electrode wall is located, and the wave troughs of the upper membrane are aligned with the wave crests of the lower membrane, with the support wall sandwiched therebetween.

[0020] In some embodiments, releasing the second material around the electrode wall comprises:

[0021] releasing the second material around the counter electrode wall by etching;

[0022] A first through hole is formed through one or both of the aligned peaks of the upper film and the valleys of the lower film to allow an etching solution to flow into the chamber through the first through hole when the second material around the counter electrode wall is released by etching.

[0023] In some embodiments, one or both of the aligned troughs of the upper film and the peaks of the lower film are penetrated to form a second through hole, which allows the etching solution to flow into the space formed between adjacent supporting walls through the second through hole when the second material surrounding the counter electrode wall is released by etching, thereby releasing the second material filled in the space formed between the adjacent supporting walls.

[0024] In some embodiments, the lower film is made of a conductive material or the lower film includes an insulating film and a conductive element disposed on the insulating film; and / or

[0025] The upper film is made of a conductive material or includes an insulating film and a conductive element disposed on the insulating film.

[0026] In another aspect, the present invention provides a micro-electromechanical system, comprising:

[0027] Conductive lower membrane;

[0028] a conductive upper film; and

[0029] A spacer layer is arranged between the lower film and the upper film, wherein the spacer layer comprises a counter electrode wall and a supporting wall, and the counter electrode wall is provided with a conductive element;

[0030] wherein a chamber is formed between the lower membrane and the upper membrane, and the electrode walls are suspended in the chamber respectively; and

[0031] The supporting walls are sandwiched between the lower membrane and the upper membrane, and spaces are formed between adjacent supporting walls.

[0032] In some embodiments, the lower film includes a plurality of alternately arranged troughs and crests; the upper film includes a plurality of alternately arranged troughs and crests;

[0033] The troughs of the lower film are aligned with the peaks of the upper film, and the peaks of the lower film are aligned with the troughs of the upper film;

[0034] The chambers are formed respectively between the aligned troughs of the lower film and the peaks of the upper film; and

[0035] The supporting walls are sandwiched between the peaks of the lower membrane and the valleys of the upper membrane, respectively.

[0036] In some embodiments, the spaces are formed between the peaks of the lower film and the valleys of the upper film, respectively.

[0037] In some embodiments, the counter electrode wall and the support wall are made of a first material, and the space is filled with a second material having a dielectric constant smaller than that of the first material.

[0038] In some embodiments, the first material is silicon nitride.

[0039] In some embodiments, the second material is silicon oxide.

[0040] In some embodiments, the chamber is isolated from the adjacent space by the corresponding supporting wall.

[0041] In some embodiments, one or both of the aligned wave crests of the upper film and the wave troughs of the lower film penetrate to form a first through hole, and the first through hole connects the chamber with the outside of the chamber.

[0042] In some embodiments, one or both of the aligned wave crests of the lower film and the wave troughs of the upper film are penetrated to form a second through hole, and the second through hole connects the space with the outside of the space.

[0043] In some embodiments, the lower film is made of a conductive material or the lower film includes an insulating film and a conductive element disposed on the insulating film; and / or

[0044] The upper film is made of a conductive material or includes an insulating film and a conductive element disposed on the insulating film.

[0045] By using spaced apart thin nitride support walls, the unwanted capacitance between the upper and lower conductive films can be reduced by 50% compared to a design using solid nitride support walls. The unwanted capacitance between the upper and lower conductive films can be further reduced by releasing the filler formed between the support walls, which can reduce the unwanted capacitance by 80% compared to a design using solid nitride support walls.

Brief Description of the Drawings

[0046] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in the field of the present invention, other drawings can be obtained based on these drawings without creative work, among which:

[0047] Figure 1 is a plan view of a micro-electromechanical system.

[0048] Figures 2 to 6 The manufacturing process of the micro-electromechanical system according to the embodiment of the present invention is shown.

[0049] Figure 7 A micro-electromechanical system according to an embodiment of the present invention. [Specific implementation method]

[0050] The specific implementation part will further illustrate the present invention with reference to the accompanying drawings. It should be noted that in all the drawings, elements with similar structures or functions are represented by similar reference numerals. The embodiments described herein are not intended to be exhaustive or descriptive of various other embodiments, or to limit the scope of the claims or the scope of some other embodiments. In addition, the embodiments shown do not need to have all the aspects or advantages shown.

[0051] refer to Figure 6 The micro-electromechanical system 10 includes a lower film 20 , an upper film 40 , and a spacer layer 60 disposed between the lower film 20 and the upper film 40 .

[0052] Specifically, the lower film 20 includes a plurality of troughs 22 and crests 24 arranged alternately. The upper film 40 includes a plurality of troughs 42 and crests 44 arranged alternately. The troughs 22 of the lower film 20 are respectively aligned with the crests 44 of the upper film 40, while the crests 24 of the lower film 20 are respectively aligned with the troughs 42 of the upper film 40. The spacer layer 60 is sandwiched between the lower film 20 and the upper film 40, and the chamber 30 is formed between the aligned troughs 22 of the lower film 20 and the crests 44 of the upper film 40.

[0053] See also Figure 1Preferably, the lower film 20, the upper film 40 and the spacer layer 60 are circular. The troughs 22, 42 and the crests 24, 44 are arc-shaped and arranged in concentric arcs with a span of less than 360 degrees. In some embodiments, each of the lower film 20 and the upper film 40 is divided into six parts in its circumferential direction. Each part includes a group of troughs 22, 42 and crests 24, 44 alternately arranged in the radial direction of the micro-electromechanical system 10. Adjacent parts are connected to each other by spokes (e.g., 26) extending in the diameter direction of the micro-electromechanical system 10. Each trough 22, 42 and crest 24, 44 spans approximately 60 degrees, and the troughs 22, 42 and crests 24, 44 are uniformly or unevenly arranged in the radial direction of the micro-electromechanical system 10. Preferably, the troughs 22, 42 and crests 24, 44 are uniformly arranged in the radial direction of the micro-electromechanical system 10. Alternatively, the lower film 20 and the upper film 40 may be divided into other numbers of parts, such as four parts or eight parts, etc. The parts may be arranged uniformly or non-uniformly in the radial direction of the micro-electromechanical system 10 .

[0054] refer to Figure 6 , the spacer layer 60 includes a plurality of counter electrode walls 62 accommodated in the chamber 30 and a plurality of support walls 64 sandwiched between the peaks 24 of the lower film 20 and the troughs 42 of the upper film 40. The spacer layer 60 has a shape similar to the lower film 20 and the upper film 40. The spacer layer 60 is divided into a plurality of parts in its circumferential direction. Each part includes a set of counter electrode walls 62 and support walls 64 alternately arranged in the radial direction of the micro-electromechanical system 10. Adjacent parts are connected to each other by spokes (e.g., 26) extending in the diameter direction of the micro-electromechanical system 10.

[0055] The electrode wall 62 is suspended in the corresponding chamber 30 by the corresponding spokes. In some embodiments, the electrode wall 62 and the support wall 64 are arc-shaped. The opposite ends of the electrode wall 62 in the circumferential direction of the micro-electromechanical system 10 are connected between adjacent spokes 26, so that the electrode wall 62 is suspended in the chamber 30. The electrode wall 62 and the support wall 64 are made of a first material preferably a nitride, such as silicon nitride. The opposite side surfaces of the electrode wall 62 facing the lower film 20 and the upper film 40 are provided with conductive elements serving as the first and second electrodes 622, 624.

[0056] A space 66 is formed between adjacent support walls 64. Chamber 30 is isolated from adjacent spaces 66 by corresponding support walls 64, and support walls 64 are respectively located between chamber 30 and adjacent spaces 66. Space 66 can be filled with filler 68, and filler 68 is made of a second material, such as an oxide, such as silicon oxide. Alternatively, space 66 between adjacent support walls 64 can be blank / empty, such as Figure 7 shown.

[0057] The lower film 20 and the upper film 40 may be made of a conductive material or include an insulating film and a conductive element disposed on the insulating film. For example, each of the lower film 20 and the upper film 40 includes a silicon nitride film with a polysilicon electrode to provide electrical conduction. Therefore, the lower film 20 and the upper film 40 are conductive. A first capacitor is formed between the lower film 20 and the first pair of electrodes 622, and a second capacitor is formed between the upper film 40 and the second pair of electrodes 624. When the lower / upper film 20 / 40 is displaced relative to the pair of electrodes 622 / 624 in response to the pressure applied thereto, the distance between the lower / upper film 20 / 40 and the opposing electrode 622 / 624 changes, so that the capacitance formed therebetween also changes, thereby generating a corresponding electrical signal.

[0058] The manufacturing process of the MEMS 10 includes the following steps:

[0059] Provide as Figure 2 The lower film 20 shown. Specifically, the lower film 20 includes a plurality of wave valleys 22 and wave crests 24 arranged alternately. The wave valleys 22 are filled with fillers 222, which may be oxides, such as silicon oxide. The top surface of the filler 222 is coplanar with the top surface of the wave crest 24.

[0060] A spacer layer 60 is formed on the lower film 20, such as Figure 3 Specifically, a spacer layer 60 is formed on the lower film 20, including:

[0061] A plurality of spaced-apart counter electrode walls 62 and support walls 64 are formed. The counter electrode wall 62 is disposed on the corresponding filler 222. The support wall 64 is disposed on the corresponding crest 24. Spaces 66 are formed between adjacent support walls 64. One or more spaces 67 are formed between the counter electrode wall 62 and the corresponding support wall 64 located on the opposite side of the counter electrode wall 62, so that a portion of the filler 222 filled in the trough 22 can be exposed through the space 67. The space 67 is isolated from the adjacent space 66 by the corresponding support wall 64 located between the space 67 and the corresponding space 66. The counter electrode wall 62 and the support wall 64 can be formed by chemical deposition. The opposite surfaces of the counter electrode wall 62 facing the lower and upper membranes 20, 40 are provided with conductive elements 622, 624, respectively.

[0062] In such Figure 4 The spaces 66, 67 formed in the spacer layer 60 are filled with a filler 68. The filler 68 is made of a second material. Preferably, the second material is an oxide, such as silicon oxide.

[0063] like Figure 5As shown, an upper film 40 is provided covering the spacer layer 60. Specifically, the upper film 40 includes a plurality of alternately arranged troughs 42 and crests 44. The troughs 22 of the lower film 20 are aligned with the corresponding crests 44 of the upper film 40. The grooves formed below the crests 44 are filled with fillers 442. The troughs 22 of the lower film 20, the corresponding crests 44 of the upper film 40 and the corresponding support walls 64 together form a closed chamber 30.

[0064] Release the filler 222, 442, 68 filled in the closed chamber 30, such as Figure 6 Specifically, the fillers 222, 442, 68 are removed by etching. A first through hole 441 is formed through one or both of the valley 22 of the lower film 20 and the corresponding peak 44 of the upper film 40 to allow the etching solution to enter the chamber 30 through the first through hole 441. In this embodiment, the first through hole 441 is formed through the peak 44 of the upper film 40.

[0065] In some embodiments, one or both of the peaks 24 of the lower film 20 and the corresponding valleys 42 of the upper film 40 are penetrated to form a second through hole 422 to allow the etching solution to enter the corresponding space 66 through the second through hole 422. In this embodiment, the valleys 42 of the upper film 40 are penetrated to form the second through hole 422. The method further releases the filler 68 filled in the space 66 formed between the support walls 64. After the filler 222, 442, 68 in the closed chamber 30 is removed, the filler 68 in the space 66 formed between the support walls 64 can be removed. Alternatively, the filler 68 in the space 66 formed between the support wall 64 and the filler 222, 442, 68 in the closed chamber 30 can be removed / released in the same step.

[0066] In the above-described embodiment, the spacer layer 60 is made of more than one material. The counter electrode wall 62 and the support wall 64 are made of nitride, and the filler 68 filled between the adjacent support walls 64 is made of an oxide having a dielectric constant smaller than that of the nitride. Therefore, the unwanted capacitance between the upper and lower conductive films 40, 20 is significantly reduced. By using spaced-apart thin nitride support walls 64, the unwanted capacitance between the upper and lower conductive films 40, 20 can be reduced by 50% compared to a design using solid nitride support walls. The unwanted capacitance between the upper and lower conductive films 40, 20 can be further reduced by releasing the filler 68 formed between the support walls 64, which can reduce the unwanted capacitance by 80% compared to a design using solid nitride support walls.

[0067] Although the present invention has been described in conjunction with one or more embodiments, the description of the above embodiments is only intended to enable those skilled in the art to practice or use the present invention. It should be understood by those skilled in the art that various modifications may be made without departing from the spirit or scope of the present invention. The above embodiments should not be construed as limiting the present invention, and the scope of the present invention is determined by reference to the following claims.

Claims

1. A process for manufacturing a micro-electromechanical system, characterized in that: The process includes: Providing a conductive lower film; A spacer layer is formed on the lower film, comprising: forming a plurality of counter electrode walls and a plurality of support walls on the lower film by using the first material, forming spaces between adjacent walls, and providing conductive elements on the counter electrode walls; and filling the space with a second material, the second material having a dielectric constant less than the dielectric constant of the first material; providing a conductive upper film overlying the spacer layer; and The second material around the counter electrode wall is released so that the portions of the lower and upper films aligned with the counter electrode wall can be displaced relative to the counter electrode wall.

2. The manufacturing process of the micro-electromechanical system according to claim 1, characterized in that: The lower film includes a plurality of wave valleys and wave peaks arranged alternately, and provides a conductive lower film, including: A lower film is provided in which the valleys are filled with the second material.

3. The manufacturing process of the micro-electromechanical system according to claim 2, characterized in that: A plurality of counter electrode walls and a plurality of supporting walls are formed on the lower membrane, including: A plurality of counter electrode walls are formed on the second material filled in the valleys of the lower film, and a plurality of support walls are formed on the peaks of the lower film.

4. The manufacturing process of the micro-electromechanical system according to claim 3, characterized in that: The upper film includes a plurality of alternately arranged troughs and crests; A conductive upper film is provided covering the spacer layer, comprising: providing a conductive upper film having recesses formed below crests thereof and filled with a second material; The wave crests of the upper membrane are aligned with the wave troughs of the lower membrane to form a chamber, in which the counter electrode wall is located, and the wave troughs of the upper membrane are aligned with the wave crests of the lower membrane, with the support wall sandwiched therebetween.

5. The manufacturing process of the micro-electromechanical system according to claim 4, characterized in that: The releasing of the second material around the electrode wall comprises: releasing the second material around the counter electrode wall by etching; A first through hole is formed through one or both of the aligned peaks of the upper film and the valleys of the lower film to allow an etching solution to flow into the chamber through the first through hole when the second material around the counter electrode wall is released by etching.

6. The manufacturing process of the micro-electromechanical system according to claim 5, characterized in that: One or both of the aligned troughs of the upper film and the peaks of the lower film penetrate to form a second through hole, and when the second material surrounding the counter electrode wall is released by etching, the etching solution is allowed to flow into the space formed between adjacent supporting walls through the second through hole to release the second material filled in the space formed between the adjacent supporting walls.

7. The manufacturing process of the micro-electromechanical system according to claim 1, characterized in that: The lower film is made of a conductive material or comprises an insulating film and a conductive element disposed on the insulating film; and / or The upper film is made of a conductive material or includes an insulating film and a conductive element disposed on the insulating film.

8. A micro-electromechanical system, comprising: Conductive lower membrane; Conductive upper film; and A spacer layer is arranged between the lower film and the upper film, wherein the spacer layer comprises a counter electrode wall and a supporting wall, and the counter electrode wall is provided with a conductive element; wherein a chamber is formed between the lower membrane and the upper membrane, and the electrode walls are suspended in the chamber respectively; and The supporting walls are sandwiched between the lower membrane and the upper membrane, and spaces are formed between adjacent supporting walls; The chamber is isolated from the adjacent space by the corresponding supporting wall, the counter electrode wall and the supporting wall are made of a first material, and the space is filled with a second material having a dielectric constant smaller than that of the first material.

9. The micro-electromechanical system of claim 8, wherein The lower membrane includes a plurality of alternately arranged troughs and crests; The upper film includes a plurality of wave valleys and wave peaks arranged alternately; The troughs of the lower film are aligned with the peaks of the upper film, and the peaks of the lower film are aligned with the troughs of the upper film; The chambers are formed respectively between the aligned troughs of the lower film and the peaks of the upper film; as well as The supporting walls are sandwiched between the peaks of the lower membrane and the valleys of the upper membrane, respectively.

10. The micro-electromechanical system according to claim 9, characterized in that: The spaces are formed between the peaks of the lower film and the valleys of the upper film, respectively.

11. The micro-electromechanical system according to claim 10, characterized in that: The first material is silicon nitride.

12. The micro-electromechanical system according to claim 10, characterized in that: The second material is silicon oxide.

13. The micro-electromechanical system according to claim 10, characterized in that: One or both of the aligned wave crests of the upper film and the wave troughs of the lower film penetrate to form a first through hole, which connects the chamber with the outside of the chamber.

14. The micro-electromechanical system according to claim 13, characterized in that: One or both of the aligned wave crests of the lower film and the wave troughs of the upper film penetrate to form a second through hole, and the second through hole connects the space with the outside of the space.

15. The micro-electromechanical system according to claim 8, characterized in that: The lower film is made of a conductive material or comprises an insulating film and a conductive element disposed on the insulating film; and / or The upper film is made of a conductive material or includes an insulating film and a conductive element disposed on the insulating film.

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