# US 7,951,636 B2 · Method for fabricating micro-electro-mechanical system (MEMS) device

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- Number: US 7,951,636 B2
- Document ID: US7951636B2
- Status: Granted
- Kind: B2
- Application number: 12/235,549
- Filed: 2008-09-22
- Published: 2010-03-25
- Granted: 2011-05-31
- Earliest claimed: 2008-09-22
- Assignees: Solid State System Co., Ltd.
- Inventors: Chien-Hsing Lee; Tsung-Min Hsieh
- Web page: https://patentgrep.com/patent/US7951636B2

## CPC

- B81C 1/00246: {Monolithic integration, i.e. micromechanical structure and electronic processing unit are integrated on the same substrate}
- B81C 1/00182: {Arrangements of deformable or non-deformable structures, e.g. membrane and cavity for use in a transducer}
- B81B 2201/0257: Microphones or microspeakers
- 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
- B81C 2203/0714: Forming the micromechanical structure with a CMOS process
- B81C 2203/0735: Post-CMOS, i.e. forming the micromechanical structure after the CMOS circuit
- H04R 19/005: {using semiconductor materials}
- H04R 19/04: Microphones (H04R19/01 takes precedence)
- H04R 31/003: {for diaphragms or their outer suspension}
- H10D 48/50: Devices controlled by mechanical forces, e.g. pressure
- B81C: PROCESSES OR APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OR TREATMENT OF MICROSTRUCTURAL DEVICES OR SYSTEMS (making microcapsules or microballoons B01J13/02; processes or apparatus specially adapted for the manufacture or treatment of piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/01)
- B81B: MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES (piezoelectric, electrostrictive or magnetostrictive elements per se H10N30/00, H10N35/00)
- H04R: LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; ELECTRIC HEARING AIDS; PUBLIC ADDRESS SYSTEMS (producing sounds with frequency not determined by supply frequency G10K)
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A micro-electro-mechanical system (MEMS) device includes a substrate, having a first side and second side, the second side has a cavity and a plurality of venting holes in the substrate at the second side with connection to the cavity. However, the cavity is included in option without absolute need. A structural dielectric layer has a dielectric structure and a conductive structure in the dielectric structure. The structural dielectric layer has a chamber in connection to the cavity by the venting holes. A suspension structure layer is formed above the chamber. An end portion is formed in the structural dielectric layer in fix position. A diaphragm has a first portion of the diaphragm fixed on the suspension structure layer while a second portion of the diaphragm is free without being fixed.

## Claims

### Claim 1

A method for fabricating a micro-electro-mechanical system (MEMS) device, comprising:
forming a first structural dielectric layer on a substrate;
patterning the first structural dielectric layer to have a plurality of indent regions without penetrating through the first structural dielectric layer;
forming a conductive diaphragm layer, wherein the conductive diaphragm layer has a corrugated structure corresponding to the indent regions, wherein the step of forming the conductive diaphragm layer comprises:
forming a first conductive layer on the first structural dielectric layer;
forming an inter-dielectric layer on the first conductive layer; and
forming a second conductive layer to cover the inter-dielectric layer, wherein the second conductive layer and the first conductive layer enclose the inter-dielectric layer;
forming a second structural dielectric layer on the first structural dielectric layer and the conductive diaphragm layer;
forming an etching mask layer on the substrate at a back surface, wherein the etching mask layer has a plurality of openings to expose the substrate, in which the openings are at positions corresponding to venting holes to be formed later; and
performing an anisotropic etching process to at least etch the substrate to expose the first structural dielectric layer, wherein the substrate has the venting holes being formed.

### Claim 2 (depends on 1)

The method of claim 1, wherein the step of forming the inter-dielectric layer comprises:
forming a dielectric layer over the first conductive layer; and
patterning the dielectric layer into a plurality of dielectric islands on the first conductive layer, adjacent to the indent regions.

### Claim 3 (depends on 1)

The method of claim 1, wherein the step of forming the inter-dielectric layer comprises:
forming a dielectric layer over the first conductive layer; and
patterning the dielectric layer into a plurality of dielectric islands on the first conductive layer, wherein the dielectric islands cover a portion of the indent regions.

### Claim 4 (depends on 1)

The method of claim 1, wherein the step of forming the inter-dielectric layer comprises:
forming a dielectric layer over the first conductive layer being conformal with the indent regions; and
patterning the dielectric layer to expose a portion of the first conductive layer, wherein a remaining portion of the dielectric layer as the inter-dielectric layer also fully covers the indent regions.

### Claim 5 (depends on 1)

The method of claim 1, wherein the first and second conductive layers are formed by polysilicon or metal.

### Claim 6 (depends on 1)

The method of claim 1, wherein the first structural dielectric layer comprises an embedded conductive structure layer.

### Claim 7 (depends on 1)

The method of claim 1, wherein the second structural dielectric layer comprises an embedded conductive structure layer.

### Claim 8 (depends on 1)

The method of claim 1, wherein in the step of forming the etching mask layer, the etching mask layer is a single etching mask layer.

### Claim 9 (depends on 1)

The method of claim 1, wherein in the etching mask layer comprises a hard mask layer or photoresist layer.

### Claim 10 (depends on 1)

The method of claim 1, wherein in the step of forming the etching mask layer, the etching mask layer has a thicker step region, surrounding the openings and corresponding to a cavity to be also formed.

### Claim 11 (depends on 10)

The method of claim 10, wherein in the etching mask layer comprises two mask layers.

### Claim 12 (depends on 11)

The method of claim 11, wherein in two mask layers comprises at least two hard mask layers or two photo resistor layers.

### Claim 13 (depends on 11)

The method of claim 11, wherein in two mask layers comprises at least a hard mask layer and a photo resistor layer.

### Claim 14 (depends on 10)

The method of claim 10, wherein the step of performing the anisotropic etching process also etches the etching mask layer to further expose the substrate and then etches the substrate just being exposed, wherein the thicker step region has a residual portion remains on the substrate.

### Claim 15 (depends on 10)

The method of claim 10, wherein the thicker step region of the etching mask layer is formed by the steps of:
forming a first mask layer with the openings, corresponding to the venting holes; and
forming a second mask layer on the first mask layer, corresponding to the cavity.

### Claim 16 (depends on 10)

The method of claim 10, wherein the thicker step region of the etching mask layer is formed by the steps of:
forming a first mask layer with a first opening to expose the substrate, corresponding to the cavity; and
forming a second mask layer on the first mask layer and the substrate, wherein the second mask layer has the openings, corresponding to the venting holes, to expose the substrate.

### Claim 17 (depends on 1)

The method of claim 1, wherein in the step of forming the second structural dielectric layer, a suspension layer is embedded in the second structural dielectric layer to adhere to a portion of the conductive diaphragm layer.

### Claim 18 (depends on 17)

The method of claim 17, wherein the suspension layer has a protrusion portion to adhere to the portion of the conductive diaphragm layer.

### Claim 19

A method for fabricating a micro-electro-mechanical system (MEMS) device comprising;
forming a first structural dielectric layer on a substrate;
patterning the first structural dielectric layer to have a plurality of indent regions without penetrating through the first structural dielectric layer;
forming a conductive diaphragm layer, wherein the conductive diaphragm layer has a corrugated structure corresponding to the indent regions;
forming a second structural dielectric layer on the first structural dielectric layer and the conductive diaphragm layer, wherein a suspension layer is embedded in the second structural dielectric layer, and the suspension layer has a protrusion portion to adhere to a portion of the conductive diaphragm layer;
forming an etching mask layer on the substrate at a back surface, wherein the etching mask layer has a plurality of openings to expose the substrate, in which the openings are at positions corresponding to venting holes to be formed later;
performing an anisotropic etching process to at least etch the substrate to expose the first structural dielectric layer, wherein the substrate has the venting holes being formed; and
performing an isotropic etching process to release the conductive diaphragm and the suspension layer, wherein the protrusion portion of the suspension layer holds the conductive diaphragm layer and a peripheral end portion of the suspension layer is clamped between the first structural dielectric layer and the second structural dielectric layer.