Analysis of plasma etching resistance for commercial quartz glasses used in semiconductor apparatus in fluorocarbon plasma

The plasma resistance of these commercial quartz glasses was compared, and the product formed by the reaction with plasma was analyzed. Plasma etching was performed in an inductively coupled plasma (ICP) process with a mixture of CF4, O2, and Ar gases. The mean etching rate of the commercial quartz glasses was 235.5㎚/min, and the p-value of 0.638 determined from the analysis of variance (ANOVA) test showed no statistical significance difference between the impurity content and the etching rate for the samples prepared by the various methods. Thus, it was determined that impurity differences on the ppm level in commercial quartz glasses does not affect the plasma resistance. After plasma etching, the surface roughness was 6.5㎛, which is 45 times greater than the initial surface roughness of 0.14㎛. This is due to the reaction product formed by the chemical reaction of SiO2 and fluorocarbon during plasma treatment. The product comprised spherical particles with a size of 5–10 ㎛, where silicon oxide and fluoride were the main reaction products, leading to coarsening of the plasma-treated quartz glass.