EFFECT OF MEMS-COMPATIBLE THIN-FILM HARD COATINGS ON THE EROSION RESISTANCE OF SILICON MICROMACHINED ATOMIZERS

A comparison of five different MEMS-compatible, thin film, hard coatin gs has been performed using silicon (Si) micromachined atomizers as te st devices. Single-crystal and polycrystalline silicon carbide, silico n nitride, silicon dioxide, and diamond-like carbon were either therma lly grown or chemically vapor deposited onto the non-planar topography of the device. Eighteen-hour long, industry-standard erosion tests we re performed to qualitatively evaluate the coatings for erosion resist ance when exposed to an aggressively contaminated test fluid. No wear was measured on the majority of the swirl chamber floor for the five c oatings, though varying degrees of erosive wear were observed at the e dge of the exit orifice. The single-crystal silicon carbide demonstrat ed the best wear performance of all the coatings, exhibiting no notice able changes of its surface morphology as a function of the erosion te sts. The silicon nitride and diamond-like carbon coatings showed the m ost wear, exhibiting micro-cracking, chipping and flaking at the exit orifice edge. (C) 1998 Published by Elsevier Science S.A. All rights r eserved.