SILICON-RICH SILICON NITRIDES AS ETCH STOP IN MEMS MANUFACTURE

• US 20080226929A1
• Filed: 05/28/2008
• Published: 09/18/2008
• Est. Priority Date: 01/18/2006
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Chung, Wonsuk, Sasagawa, Teruo, Zee, Steve
• Granted Patent: US 8,064,124 B2
• Time in Patent Office: Days
• US Class Current: 428/457
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81C 1/00801 Avoid alteration of functional structures by etching, e.g. using a passivation layer or an etch stop layer B81C1/00595, B81C1/00468 take precedence
• CPC Class Codes: B81C 2201/014 by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: Y10T 428/31678 Of metal

Abstract

The fabrication of a MEMS device such as an interferometric modulator is improved by employing an etch stop layer between a sacrificial layer and a an electrode. The etch stop may reduce undesirable over-etching of the sacrificial layer and the electrode. The etch stop layer may also serve as a barrier layer, buffer layer, and/or template layer. The etch stop layer may include silicon-rich silicon nitride.

Claims

1. An unreleased interferometric modulator, comprising:

an etch stop layer positioned between a sacrificial layer and a metal mirror layer, wherein the metal mirror layer is adapted to be movable upon removal of the sacrificial layer and the etch stop layer is adapted to be substantially completely removed upon exposure to XeF₂ for less than about 10 minutes.

2. The unreleased interferometric modulator of claim 1, wherein the metal mirror layer is positioned over the sacrificial layer.

3. The unreleased interferometric modulator of claim 1, wherein the etch stop layer comprises a silicon nitride.

4. The unreleased interferometric modulator of claim 3, wherein the ratio of silicon to nitrogen in the silicon nitride layer is greater than about 3:

4.

5. The unreleased interferometric modulator of claim 4, wherein the ratio of silicon to nitrogen in the silicon nitride layer is greater than about 1:

1.

6. The unreleased interferometric modulator of claim 1, wherein the sacrificial layer is also adapted to be substantially completely removed upon exposure to XeF₂.

7. The unreleased interferometric modulator of claim 1, wherein the sacrificial layer is selected from the group consisting of molybdenum and amorphous silicon and the electrode layer comprises aluminum.

8. An unreleased interferometric modulator, comprising:

means for reflecting light;

means for supporting the reflecting means during interferometric modulator manufacture; and

means for protecting the supporting means during etching of the reflecting means.

9. The unreleased interferometric modulator of claim 8, wherein the reflecting means is a metal mirror.

10. The unreleased interferometric modulator of claim 8, wherein the supporting means is a sacrificial layer.

11. The unreleased interferometric modulator of claim 8, wherein the protecting means is a silicon nitride layer and wherein the ratio of silicon to nitrogen in the silicon nitride layer is greater than about 3:

4.

12. The unreleased interferometric modulator of claim 11, wherein the ratio of silicon to nitrogen in the silicon nitride layer is greater than about 1:

1.