In-situ spectral ellipsometry monitoring/control of MBE growth

Abstract

Spectroscopic ellipsometry (SE) has received considerable attention for semiconductor growth monitoring and control due to its ability to determine the thickness and composition of thin parallel layers. In this work, we report on the use of spectroscopic ellipsometry for monitoring and control of AlGaAs growth in molecular beam epitaxy. Knowledge of the optical constants as a function of composition and growth parameters is essential for modeling to be able to extract the composition and growth rate from measured SE data. For this work, we have used the virtual interface approximation to extract the growth rate and composition of of Al/sub x/Ga/sub 1-x/As films grown at normal and elevated temperatures. At elevated temperatures, Ga possessed a sticking coefficient less than 1. 900 K Ga was observed to grow at a constant rate. At elevated temperatures the Ga growth rate decreased until at 940 K no continued growth was observed. Under all conditions SE accurately predicted the observed growth rates.