<title>Surface preparation for selective tungsten deposition on MEMS structures</title>

Abstract

Selectively deposited tungsten films on MEMS surfaces that are subject to friction and wear can substantially reduce wear-related failures. Because deposition of the tungsten film is highly selective to silicon, a pristine surface is required to obtain high quality, contiguous films. Vapor phase HF was used to remove the thin chemical oxide that resides on the surface following traditional liquid phase dissolution of sacrificial oxide films and supercritical CO 2 drying of MEMS devices. The use of vapor phase HF after mechanical parts have been released, rather than liquid processes, mitigates potential device damage and surface tension-induced stiction that may occur during liquid phase processing. Tungsten film thickness and morphology were identical to films that were obtained through the use of liquid phase pre-cleaning processes.