High-Rate Epitaxial Growth of Silicon Using Electron Beam Evaporation at High Temperatures

This paper describes the high-rate (similar to 1.5 mu m/min) growth of Si films on Si supporting substrates with (100) crystallographic orientation at 600 degrees C, 800 degrees C, and 1000 degrees C in a vacuum environment of similar to 1 x 10(-5) mbar using electron beam (e-beam) evaporation. The microstructure, crystallinity, and conductivity of such films were investigated. It was established that fully crystalline (Raman spectroscopy, EBSD) and stress-free epi-Si layers with a thickness of approximately 50 mu m can be fabricated at 1000 degrees C, while at 600 degrees C and 800 degrees C, some poly-Si inclusions were observed using Raman spectroscopy. Hall effect measurements showed that epi-Si layers deposited at 1000 degrees C had resistivity, carrier concentration, and mobility comparable to those obtained for c-Si wafers fabricated through ingot growth and wafering using the same solar grade Si feedstock used for the e-beam depositions. The dislocation densities were determined to be similar to 2 x 10(7) cm(-2) and similar to 5 x 10(6) cm(-2) at 800 and 1000 degrees C, respectively, using Secco etch. The results highlight the potential of e-beam evaporation as a promising and cost-effective alternative to conventional CVD for the growth of epi-Si layers and, potentially, epi-Si wafers. Some of the remaining technical challenges of this deposition technology are briefly indicated and discussed.