Reducing MEMS stiction by deposition of nanoclusters
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.
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.