Acoustic Wave Inspection of SOI Substrates for Space System Applications

SIMOX (Separation by IMplanted OXygen) technology achieves total dielectric isolation of active device regions from the substrate and reduces the collection path for ionized charges via the built-in buried oxide which restricts charge movement. Advances in SIMOX technology include radiation hardened memories and gate arrays for space applications, ULSI DRAMs for low voltage operation, thin film low power/low voltage circuitry, and extreme (400 degree C) temperature applications of SIMOX circuitry. A significant aspect regarding device reliability and performance is the silicon dislocation density in the starting surface of the SOI substrates. However, optically counting etch pits for material etch pit densities ranging from 1E2/cm2 to 1E8/cm2 (depending on the material processing) is extremely time consuming and precludes immediate production feedback. This Phase I proposal examines the feasibility of an impulsive stimulated thermal scattering method which may be applicable for non-destructively examining Si dislocations. In Phase I, we will investigate the effect of the acoustic wave analysis on both etched and unetched samples as compared with the destructive chemical analysis. In Phase II, if feasibility is proven, we will carry out research and development necessary to provide an accurate, automatic, non-destructive dislocation density evaluation technique for substrate production and improvement programs. Phase III commercialization includes Phase II instrument planning and partnership considerations.