Linewidth control and profile contouring of polysilicon by anisotropic plasma etching with Freon 115, (CC1F5), and Freon 115/oxygen gas mixtures were investigated utilizing an LFE model 1002-P plana plasma etcher with a laser interferometric endpoint detector. It was found that Freon 115 etches anisotropicly with a reentrant edge profile and good photoresist and Si02 etch selectivity. A slight amount of undercutting was observed with overetching and was found to be related to trace amounts of oxygen in the Freon 115 plasma discharge. Freon 115/oxygen mixtures were investigated. It was determined that the polysilicon etch rate and the degree of anisotropy depends strongly on the oxygen concentration. Various combinations of anisotropic/isotropic etch sequences were found to have useful polysilicon edge contouring properties.