Optical diagnostics for epitaxial growth and processing

Increasing complexity, more stringent tolerances on layer compositions and thicknesses, the trend toward chemical deposition methods, and the need to maintain satisfactory yields despite increasing economic pressures have created the need to obtain real-time information about epitaxial growth. Optical probes are attractive for real-time applications because they are noninvasive and can be used in any transparent ambient, including the high pressure ambients used for organometallic chemical vapor deposition (OMCVD). Traditional difficulties regarding surface sensitivity have been overcome by the invention of new, submonolayer-sensitive techniques such as reflectance-difference (-anisotropy) spectroscopy (RDS/RAS) and surface photoabsorption (SPA) and by the improvement of existing techniques such as laser light scattering (LLS) and spectroellipsometry. Recently invented minimal-data algorithms have provided a new, near-surface analytic capability that allows information to be obtained about the outermost region of a layer during deposition or etching, even if nothing is known about the underlying structure