Mems transducer and manufacturing method therefor

• US 20090200620A1
• Filed: 12/23/2008
• Published: 08/13/2009
• Est. Priority Date: 12/28/2007
• Status: Active Grant

• Current Assignee: Yamaha Corporation
• Original Assignee: Yamaha Corporation
• Inventors: Omura, Masayoshi, Suzuki, Tamito, Suzuki, Yukitoshi
• Granted Patent: US 7,888,754 B2
• Time in Patent Office: Days
• US Class Current: 257/419
• CPC Class Codes: B81B 2201/0257 Microphones or microspeakers
• CPC Class Codes: B81B 2203/0127 Diaphragms, i.e. structures separating two media that can control the passage from one medium to another; Membranes, i.e. diaphragms with filtering function
• CPC Class Codes: B81B 2203/04 Electrodes
• CPC Class Codes: B81B 3/0021 Transducers for transforming electrical into mechanical energy or vice versa dynamo-electric machines H02K99/00; electrostatic machines H02N1/00; piezoelectric devices H10N30/00
• CPC Class Codes: H01L 29/84 controllable by variation of applied mechanical force, e.g. of pressure

Abstract

An MEMS transducer is constituted of a diaphragm, a plate, a support structure for supporting the diaphragm and the plate with a gap layer surrounded by an interior wall, an electrode film (e.g. a pad conductive film) for covering a contact hole formed in the support structure, and a protective film (e.g. a pad protective film) which is formed on the support structure externally of the interior wall so as to cover the side surface of the electrode film having low chemical stability. The protective film is formed in the limited area including a part of the surface of the electrode film except for its center portion and the surrounding area of the electrode film. This allows the protective film to use materials having high membrane stress such as silicon nitride or silicon nitride oxide.

Claims

1. An MEMS transducer comprising:

a diaphragm having conductivity;

a plate having conductivity;

a support structure for supporting the diaphragm and the plate with a gap layer therebetween, wherein the support structure has an interior wall surrounding the gap layer;

an electrode film having conductivity for covering a contact hole formed in the support structure; and

a protective film which is formed on the support structure externally of the interior wall so as to cover a side surface of the electrode film,

wherein an electric signal corresponding to variations of an electrostatic capacitance formed between the diaphragm and the plate is output via the electrode film.

2. An MEMS transducer according to claim 1, wherein the protective film is composed of silicon nitride or silicon nitride oxide.

3. An MEMS transducer according to claim 2, wherein the support structure has a multilayered structure including a silicon substrate and a silicon oxide film which joins the silicon substrate except for its periphery, and wherein the protective film is formed in a region extended between the periphery of the silicon substrate and a periphery of the silicon oxide film.

4. A manufacturing method of an MEMS transducer including a diaphragm having conductivity and a plate having conductivity, comprising:

supporting the diaphragm and the plate with a gap layer therebetween by means of a support structure having an interior wall surrounding the gap layer;

forming a contact hole in the support structure;

forming an electrode film having conductivity which covers the contact hole; and

forming a protective film for covering a side surface of the electrode film externally of the interior wall of the support structure.

5. An MEMS transducer comprising:

a diaphragm having conductivity;

a plate having conductivity;

an insulating member for insulating the diaphragm from the plate;

an electrode film which is composed of a conductive film so as to cover a contact hole formed in the insulating member; and

a protective film which is limitedly formed in a part of a surface of the electrode film and a surrounding area of the electrode film on a surface of the insulating member, thus covering a side surface of the electrode film,

wherein an electric signal corresponding to variations of electrostatic capacitance formed between the diaphragm and the plate is output from the electrode film.

6. An MEMS transducer according to claim 5, wherein the protective film is composed of silicon nitride or silicon nitride oxide.

7. An MEMS transducer according to claim 5, wherein the protective film is formed on the surface of the electrode film except for its center portion.

8. A manufacturing method of an MEMS transducer including a diaphragm, a plate, and an insulating member, comprising:

forming a contact hole in the insulating member which insulates the diaphragm from the plate;

forming an electrode film covering the contact hole of the insulating member; and

limitedly forming a protective film on a part of a surface of the electrode film and a surrounding area of the electrode film on a surface of the insulating member, thus covering a side surface of the electrode film.

9. The manufacturing method of an MEMS transducer, wherein the protective film is formed on the surface of the electrode film except for its center portion.