Reducing MEMS stiction by deposition of nanoclusters

• US 9,434,602 B2
• Filed: 07/30/2014
• Issued: 09/06/2016
• Est. Priority Date: 07/30/2014
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Steimle, Robert F., Montez, Ruben B.
• Primary Examiner(s): Sarkar, Asok K
• Application Number:
  US14/446,910
• Publication Number:
  US 20160031698A1
• Time in Patent Office: 769 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2203/0181 See-saws
• CPC Class Codes: B81B 3/001 Structures having a reduced contact area, e.g. with bumps or with a textured surface

Abstract

Certain microelectromechanical systems (MEMS) devices, and methods of creating them, are disclosed. The method may include forming a structural layer over a substrate; forming a mask layer over the structural layer, wherein the mask layer is formed with a material selective to an etching process; forming a plurality of nanoclusters on the mask layer; and etching the structural layer using at least the etching process.

Claims

1. A method for manufacturing a microelectromechanical systems (MEMS) device, the method comprising:

forming a structural layer over a substrate;

forming a mask layer over the structural layer, wherein the mask layer is formed with a material selective to an etching process;

forming a plurality of nanoclusters on the mask layer;

using the nanoclusters as a mask for removing portions of the mask layer; and

etching the structural layer using remaining portions of the mask layer as a mask for the etching of the structural layer forming a plurality of surface roughness features on a travel stop of the MEMS device.

2. The method of claim 1, wherein the etching process comprises:

a first etching process for the removing portions of the mask layer; and

a second etching process operable to etch the structural layer.

3. The method of claim 2, wherein performing the second etching process further comprises removing the plurality of nanoclusters.

4. The method of claim 1, wherein the etching process comprises an anisotropic etch.

5. The method of claim 1, wherein the etching process comprises an isotropic etch.

6. The method of claim 1, further comprises:

forming a sacrificial layer on the etched structural layer; and

forming a second structural layer over the sacrificial layer.

7. The method of claim 6, further comprising planarizing a portion of the sacrificial layer prior to forming the second structural layer.

8. The method of claim 1, wherein a nanocluster comprises one of silicon carbide, silicon germanium, polysilicon, silicon, or germanium, wherein the nanocluster is one of the plurality of nanoclusters.

9. The method of claim 1, wherein the structural layer comprises a polysilicon layer.

10. The method of claim 1, wherein the material selective to the etching process comprises a silicon oxide.

11. A method for manufacturing a microelectromechanical systems (MEMS) device, the method comprising:

forming a structural layer over a substrate;

forming a mask layer over the structural layer;

forming a plurality of nanoclusters on the mask layer;

using the nanoclusters as a mask for removing portions of the mask layer; and

etching the structural layer using remaining portions of the mask layer as a mask for the etching of the structural layer forming a plurality of surface roughness features of a travel stop feature of the MEMS device; and

forming a movable body, wherein the structural layer forms a fixed surface having a portion facing a major surface of the movable body, and the fixed surface is operable to contact at least a portion of the plurality of surface roughness features.

12. The method of claim 11, further comprising:

forming a sacrificial layer on the etched structural layer; and

forming a second structural layer over the sacrificial layer.

13. The method of claim 11, wherein the movable body comprises:

a pivoting proof mass of a teeter-totter accelerometer;

the travel stop feature is configured to contact the structural layer to prevent over rotation of the pivoting proof mass, and comprises a portion of the major surface facing the fixed surface.

14. The method of claim 13, wherein:

a portion of the travel stop feature is formed using a process comprising;

forming a sacrificial layer on the etched structural layer; and

forming a second structural layer over the sacrificial layer.

15. The method of claim 14, wherein the portion of the travel stop feature is formed using a process further comprising planarizing a portion of the sacrificial layer prior to forming the second structural layer.

16. The method of claim 11, wherein the plurality of nanoclusters are formed of one of silicon carbide, silicon germanium, polysilicon, silicon, or germanium.