Effects of gas-flow structures on radical and etch-product density distributions on wafers in magnetomicrowave plasma etching reactors

To achieve high etch rate, uniformity, good selectivity, and etch profile c ontrol across large diameter wafers, the distributions of ions, radicals, a nd etch products in magnetomicrowave high-etch-rate plasma etching reactors must be accurately controlled. In this work the effects of chamber heights , a focus ring around the wafer, and gas supply structures (or gas how stru ctures) on the radicals and etch products flux distribution onto the wafer were examined using the direct simulation Monte Carlo method and used to de termine the optimal reactor geometry. The pressure uniformity on the wafer was less than +/-1% when the chamber height was taller than 60 mm. The focu s ring around the wafer produced uniform radical and etch-product fluxes bu t increased the etch-product flux on the wafer. A downward-how gas-supply s tructure (type II) produced a more uniform radical distribution than that p roduced by a radial gas-supply structure (type I). The impact how of the ty pe II structure removed etch products from the wafer effectively and produc ed a uniform etch-product distribution even without the focus ring. Thus th e downward-flow gas-supply structure (type II) was adopted in the design fo r the second-generation of a magnetomicrowave plasma etching reactor with a higher etching rate. (C) 2001 American Vacuum Society.