Failure of Large-Area Epitaxial-Diffused Silicon Devices

The Structural perfection of the epitaxial-diffused silicon films is one of the most important factors determining the performance and reliability of large-area epitaxial-diffused devices. The characteristics of these devices are affected by structural imperfections generated during the epitaxial growth and the diffusion processes. The commonly observed imperfections in epitaxial silicon films are dislocations, stacking faults, growth pyramids, and polycrystalline inclusions. They all have adverse effects of varying degrees on device characteristics. Except those propagated from the substrate, structural imperfections in epitaxial silicon films can be essentially eliminated by using proper growth techniques. The diffusion of high concentrations of dopants into epitaxial silicon films has been shown to generate dislocations and to transform stacking faults into other types of imperfections. furthermore, localized areas of high dislocation density in epitaxial-diffused silicon films, due to contamination and improper handling techniques, have been shown to be responsible for the softness of large-area epitaxial-diffused junctions. The characteristics of these junctions were found to be improved considerably by using a gettering technique. The epitaxial growth technique has been shown to be a valuable substitute for diffusion in reducing the failure of certain large area devices.