Modeling the uniformity in a magnetron etching system

Abstract

Magnetically enhanced reactive ion etch (MERIE) systems are increasingly popular for etching applications which demand high anisotropy and high etch rates without sacrificing etch selectivity. Conventional planar magnetron etch systems in which the magnetic fields are radial, exhibit a nonuniform race track etch. We report on an adjustable, rotating field, planar MERIE system. An etch uniformity of ±5% (6 in. wafer diameter) for resist etching in an O2 plasma has been obtained over a wide range of conditions. The impact of magnetic field adjustment and contoured electrodes on resist etch uniformity is characterized. An equivalent circuit model coupled with a diffusion model, and a Monte Carlo simulation of secondary electron transport have been used to predict the spatial distribution of plasma parameters in an Ar plasma sustained between planar electrodes. The measured magnetic field distribution, radio-frequency power, current, and voltage are used as inputs to the model. The spatial distribution of the magnetic field has a profound influence on the plasma parameters. The calculated spatial distribution of the ion flux in an Ar plasma is in qualitative agreement with the resist etch rate distribution across the wafer in an O2 plasma.