Profile evolution simulator for sputtering and ion-enhanced chemical etching

Abstract

A plasma etching profile simulator was developed to investigate the evolution of pattern profiles in various materials under different plasma conditions. This simulator is based on a two-dimensional cellular method. The model is fed with input parameters that include angular dependent etch yield, ion and neutral angular distribution, and plasma and material characteristics. It has been tested by comparison with published profiles of Si sputtering and SiO2 ion-assisted chemical etching in argon and chlorine plasmas. Observed microtrenching and bowing have been well reproduced by the simulator. The simulator was further used to examine etching for dimensions below nanometer in low-pressure high-density plasmas. In the case of Si sputtering, trenches of 100 nm depth and 30 nm or less width show unusual lateral etching. Finally, the effect of positive charge accumulation on an insulated mask resulting from negative bias voltage on the wafer was studied. This charge accumulation causes a deflection of ion trajectories. Considering this phenomenon, very isotropic etched profiles were found, in good agreement with in-house experimental profiles of platinum sputtering in argon plasma. The simulator developed is intended to be used for any material and mask combination in order to predict the profile evolution under various plasma conditions and pattern dimensions from micrometer to nanometer.