Three-Dimensional Atomic-Scale Cellular Model and Feature Profile Evolution during Si Etching in Chlorine-Based Plasmas: Analysis of Profile Anomalies and Surface Roughness

Abstract

Three-dimensional measurement and prediction of atomic-scale surface roughness on etched features become increasingly important for the fabrication of next-generation devices; however, the feature profiles are too small or too complex to measure the surface roughness on bottom surfaces and sidewalls of the etched features. To predict the surface roughness on an atomic or nanometer scale, we developed our own three-dimensional atomic-scale cellular model (ASCeM-3D) and feature profile simulation, with emphasis being placed on the formation of surface roughness on the atomic scale soon after the start of Si etching in Cl2 plasmas. Numerical results indicated that nanometer-scale convex roughened features appear on the surface soon after the start of etching, which causes the formation of a larger surface roughness, and that the surface roughness tends to be saturated after several seconds. In effect, the nanoscale convex features increase in size with increasing etching or plasma exposure time, and new nanoscale convex ones continue to appear on top of the enlarged convex ones during etching, thus resulting in concavo-convex features superimposed on the roughened surface. A comparison was also made between numerical results and experiments.