ECR-PLASMA ETCHING OF SILICON-NITRIDE CERAMICS

Electron-cyclotron-resonance (ECR) plasma etching was applied to gas pressure sintered Si3N4, beta'-SiAlON and alpha'/beta' composite SiAlON. The etching was successfully performed within about 15 min, and the shapes of Si3N4 and SiAlON grains were clearly observed. Also the grains of alpha'-SiAlON were distinguishable from beta'-SiAlON grains and grain boundaries. The volume ratio of alpha' phase to beta' phase obtained from the area of the etched surface was almost consistent with the value obtained from X-ray diffraction. However, the grain boundary area observed from the etched surface did not correspond to that obtained from back scattered electron image.