Real-Time Feedback Control of Thermal CL2 Etching of GaAs Based on In-Situ Spectroscopic Ellipsometry

Abstract

ABSTRACTIn-situ, real-time, spectroscopic ellipsometry (SE) is utilized to study thermal chlorine etching of GaAs in an all ultra-high-vacuum interconnected growth and etching system. In the low temperature (between ˜40°C and ˜120°C) range, the etch rate is found to exhibit an Arrhenius dependence on substrate temperature with an activation energy of 11.6Kcal/mole and to be proportional to essentially the square root of the chlorine pressure. An SE feedback based real-time etch process control algorithm is developed and successfully implemented on the basis of the above noted input - output relation derived from the experimental data base.