M. Tao et Lp. Hunt, CRYSTAL-GROWTH IN SILICON CHEMICAL-VAPOR-DEPOSITION FROM SILANE - THEROLE OF HYDROGEN, Journal of the Electrochemical Society, 144(6), 1997, pp. 2221-2225
Crystal growth mechanisms in chemical vapor deposition (CVD) of silane
are studied in some detail. An atomic view reveals that the free ener
gy change upon the formation of a small crystal on the (100) silicon s
urface in Si-CVD from SiH4 is always negative, due to the presence of
hydrogen. Therefore, nucleation and step growth are unnecessary, in co
ntrast to crystal growth from melt. Epitaxial growth in this case take
s place through iterative adsorption and desorption reactions on the p
eriodic surface sites of the substrate. Slow desorption reactions resu
lt in vacancies and distorted bond angles which hinder epitaxial growt
h. Based on this model, the role of H desorption in low temperature Si
epitaxy from SiH4 is investigated. A thermodynamic analysis implies t
hat H desorption is the limiting factor to low temperature epitaxy in
the pressure range of 1 to 760 Torr, and the pressure dependence of mi
nimum epitaxial temperature is derived as T-epi(degrees C) = 106 log P
-tot(Torr) + 668. Below 1 Torr, adsorption rate becomes the limiting f
actor to low temperature epitaxy.