Solid-phase crystallization of amorphous SiGe films deposited by LPCVD on SiO2 and glass

The crystallization kinetics and film microstructure of poly-SiGe layers obtained by solid-phase crystallization (SPC) of amorphous SiGe with Ge fractions (x) in the 0 to 0.42 range have been studied in detail. Amorphous SiGe layers 100 nm thick were deposited by LPCVD at 450 degrees C on thermally oxidized Si wafers and 7059 Coming glasses, using Si2H6 and GeH4 as gas sources. The samples were crystallized at 550 degrees C and low pressure (below 9 Pa). The evolution of the crystallization and the resulting film microstructure were characterized by X-ray diffractometry and transmission electron microscopy. The experimental results on growth kinetics fit the Avrami's model. The characteristic crystallization time decreases with x, slowly for x < 0.3 and more abruptly for higher values of x. The transient time depends exponentially on x in all the intervals. The crystallized films have a (111) preferred orientation for low values of x and evolve to a randomly oriented polycrystal as x increases. The grain size in the fully crystallized layers decreases with increasing x. The results are similar for the films deposited on silicon dioxide and glass. (C) 1999 Elsevier Science S.A. All rights reserved.