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°C on thermally oxidized Si wafers and 7059 Corning glasses, using Si₂H₆ and GeH₄ as gas sources. The samples were crystallized at 550°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.