| Popis: |
The stated objectives of this research effort were directed at: (1) The establishment of magnetic LP-LEC growth capability with diameters approaching 4 inches; (2) The design of heat and mass transfer control systems required for optimization of growth with magnetic melt stabilization, and (3) Development of a model-based growth control scheme which includes complementary knowledge-based system inputs for seeding, shouldering, and growth termination. A non-invasive wafer inspection system has been developed. It is based on NIR transmission microscopy with bright and dark field illumination. It provides for rapid quantitative characterization of doped and non-doped SI GaAs on both a macro- and selected microscale. Model-based control of thermal stresses in LEC growth of GaAs has been implemented. In this approach mathematical models of the growth process and a heat exchange system are used to control the temperature field in the crystal during growth and cooldown. Crystals grown in this configuration exhibit dislocation densities in the range of 1000/sq. cm. Also developed was a micro-mechanical constitutive law for high temperature creep and dislocation multiplication in GaAs. |
