Real-time optical control of epitaxial III-V semiconductor composition and structure

Real-time control of epitaxial crystal growth is a necessity for the production of advanced materials in order to improve the yields of new generations of digital, RF, and optoelectronic devices. Process tolerances are becoming tighter in terms of both layer stoichiometry and layer thickness. The traditional grow-characterize-grow again technique that has served us well over past decades is no longer a production worthy method of ensuring that wafers grown after calibration meet the design specifications. The day to day drift in most epitaxial growth systems is often as great as the wafer specification window. In this paper we describe a spectroscopic ellipsometer based control system and present results obtained for GaAs-AlGaAs structures grown by organometallic molecular beam epitaxy.