REAL-TIME OPTICAL DIAGNOSTICS FOR EPITAXIAL-GROWTH

A variety of optical methods is now available for studying surface processes and for monitoring layer thicknesses and compositions during semiconductor crystal growth by molecular beam epitaxy, organometallic chemical vapor deposition, and related techniques. New capabilities for surface analysis are provided by new techniques such as reflectance-difference spectroscopy, which use intrinsic symmetries to suppress ordinarily dominant bulk contributions. Bulk and microstructural properties such as compositions and layer thicknesses can be determined directly by techniques such as spectroellipsometry, which return information integrated over the penetration depth of light. Proven capabilities suggest new applications to interrupted growth and to metastable materials systems involving self-ordering and strain relaxation. The first closed-loop system for controlling semiconductor crystal growth, which uses a spectroellipsometer as the monitoring element, is briefly described.