Real time characterization of plasma etch selectivity

Summary form only given. In-situ real-time measurement of thin film etching and deposition is necessary for semiconductor process development as well as monitoring and control. The relatively high process rates in high density plasma tools and the shrinking thickness of the films, call for a fast estimate of the process rates. Two-color laser interferometry operated at two locations is used to determine in real-time, within a second, the etch rate and thickness of two thin transparent films. The advantages of two-color laser interferometry will be described. The selectivity of the process is calculated from the ratio of the instantaneous process rates of the films as a function of the tool state. The experiment is carried out in a magnetically confined ICP tool. The tool state, gas flow, pressure, and RF power to the antenna and the electrostatic chuck, used to bias and cool the wafer, are computer controlled and monitored. The etch selectivity of polysilicon and SiO/sub 2/ films using Cl/sub 2/, CF/sub 4/ and CHF/sub 3/ gases over a large parameter space of tool states will be described. The experimental setup is configured to utilize both single and double laser points. Both schemes are used to determine the etch rate of the two films.