On the Dry Etch Mechanisms of Y2O3, SiO2, and Si3N4 in a Cl-2/BCl3 Inductively Coupled Plasma

Abstract

This paper deals with a model-based study of Y2O3, SiO2, and Si3N4 etch mechanisms in a Cl-2/BCl3 inductively coupled plasma. Both etching and plasma diagnostics experiments were carried out at constant total gas pressure (6 mTorr), gas flow rate (40 scan), input power (700 W) and bias power (300 W) while the gas mixing ratio was used as the variable parameter. The Y2O3 etch rate was found to increase by more than 2 times for 0 - 100% BCl3 in the Cl-2/BCl3 gas mixture while both the SiO2 and the Si3N4 etch rates exhibited a maximum at 40 - 50% BCl3. Using a model-based analysis of the plasma chemistry and the etch kinetics, the behavior of the Y2O3 etch rate was demonstrated to correspond to the ion-flux-limited etch region while the etch kinetics were significantly influenced by the presence BClx radicals. The non-monotonic behaviors of the SiO2 and the Si3N4 etch rates may result from the concurrence of chemical and physical etch pathways in a transitional region.