RIEのシース内におけるイオン散乱確率

抄録

Ion scattering in the sheath of a glow discharge used for reactive ion etching is discussed. Ions arriving at the target must cross the sheath; consequently, at higher pressures many inclined ion trajectories are generated due to collisions with ambient sheath molecules. To obtain a vertical etching profile, it is, therefore, necessary to know the amount of inclined ions. The scattering probability depends on the sheath thickness and the ion mean free path when considering the ion energy dependence of the collision cross section. The effect of ion energy on the scattering probability has been calculated for Ar and found to be significant in typical reactive ion etching conditions. Calculations based on the experimental data of CF₄ plasma parameters show that the scattering probability decreases with decreasing pressure and power density. Therefore, for the condition that the etching reaction is induced by ion bombardment, a vertical etching profile can be predicted.