Reducing MEMS stiction by deposition of nanoclusters
View Patent ↗A mechanism for reducing stiction in a MEMS device by decreasing surface area between two surfaces that can come into close contact is provided. Reduction in contact surface area is achieved by increasing surface roughness of one or both of the surfaces. The increased roughness is provided by forming a micro-masking layer on a sacrificial layer used in formation of the MEMS device, and then etching the surface of the sacrificial layer. The micro-masking layer can be formed using nanoclusters. When a next portion of the MEMS device is formed on the sacrificial layer, this portion will take on the roughness characteristics imparted on the sacrificial layer by the etch process. The rougher surface decreases the surface area available for contact in the MEMS device and, in turn, decreases the area through which stiction can be imparted.
1. A method for manufacturing a microelectromechanical systems (MEMS) device, the method comprising:
forming a fixed surface;
forming a movable body providing a major surface facing the fixed surface, wherein
at least a portion of the major surface is configured to contact at least a portion of the fixed surface; and
forming the portion of the major surface configured to contact the portion of the fixed surface such that the portion of the major surface comprises a surface roughness at least five times greater than a non-roughened portion of the major surface, wherein said forming the portion of the first major surface such that the portion of the major surface comprises a surface roughness at least five times greater than a non-roughened portion of the major surface comprises:
forming a sacrificial layer over the fixed surface,
forming a plurality of nanoclusters on the sacrificial layer,
etching the sacrificial layer using a wet etch process subsequent to said forming the plurality of nanoclusters, wherein the wet etch is selective to the sacrificial layer, the nanoclusters provide a micro-masking layer for said etching, and said etching increases roughness of the surface of the sacrificial layer as compared to the roughness of the surface upon said forming the sacrificial layer, and
forming the movable body on the sacrificial layer subsequent to said etching the sacrificial layer, wherein the at least a portion of the major surface configured to contact at least a portion of the fixed surface is formed in contact with the etched sacrificial layer.
2. The method of claim 1 wherein said forming the plurality of nanoclusters comprises:
performing a low temperature deposition of nanocluster material; and
performing an anneal to form the nanoclusters.
3. The method of claim 2 wherein said performing the low temperature deposition of nanocluster material further comprises:
depositing sufficient material to form nanoclusters having a diameter of approximately 20 nm or greater upon performing said annealing, wherein a size of the nanoclusters is proportional to a time period of the low temperature deposition of nanocluster material.