Dense Yttria Film Deposited on a Plasma-Sprayed Al2Oз Coating by Aerosol Deposition

Keywords: Yttria film, alumina, surface roughness, grit blasting, aerosol deposition
The aim is to select the conditions for obtaining good adhesion on the surface of aluminum oxide, to protect it from the plasma.

Introduction
Chamber parts of semiconductor processing and flat- panel-display processing equipment often need electrical insulation and chemical protection. Sintered ce­ramics including alumina, aluminum nitride and others have been used for such parts owing to their excellent electrical property and chemical stability.

However, recent progress requires scale-up of the production equipment and the chamber parts. This becomes more difficult, expensive and time-consuming as the size of part to be sintered is increased. For making some of the large parts, ceramic coating might be an alternative.

Methodology
the substrate was fixed onto a motored stage using double-sided tape in the deposition chamber, which was evacuated by a rotary pump with mechanical booster pump. The substrate surface was positioned 10 mm away from the nozzle and reciprocally moved 15 times at 10 mm/s.

SEM micrograph of sample 3; high magnification showing the alumina coating and yttria film.
Yttria particles were sprayed onto 20 mm x 20 mm surface of the alumina through a nozzle with slit-type opening of 0.8 mm x 35 mm in the deposi­tion chamber.

Result
In this study, the optimum average surface roughness (Ra) value was between 0.5 im and 1.8 im. Aerosol deposition of dense yttria film improved the CF4 + Ar plasma erosion resistance of the porous plasma-sprayed alumina coating by about eight times.