Neutral uniformity and transport mechanisms for plasma etching

Dissociated neutral (radical) uniformity on the wafer has been studied in a high-density large area plasma reactor. Radial profiles of radicals on the wafer are measured by scanning optical probe and by spatially resolved actinometry and are also estimated by a simple analytic model and two-dimensional (2D) commercial fluid simulation code. Center-peaked radial profiles of radical species are observed experimentally and are also predicted by simple calculation and by simulation code. The radial radical density profiles are compared with the radial profiles of etching rate of blanket photoresist films on 200 mm wafers etched by oxygen plasmas. Radial profiles of etch rate and atomic oxygen radical densities are compared and discussed along with other parameters such as the profiles of ion density, ion energy, and wafer temperature with various chuck bias voltages. At low chuck bias voltage the etch rate uniformity is correlated with radical uniformity. As the chuck bias voltage increases, the etch rate profile begins to follow the ion density profile. (C) 2001 American Institute of Physics.