Effect of deposition parameters on the characteristics of low-pressure chemical vapor deposited SiGe films grown from Si2H6 and GeH4

The growth rate, composition, and crystallinity of SiGe layers deposited in a hot-wall low-pressure chemical vapor deposition system, using disilane and germane as source gases, have been analyzed as functions of the deposition parameters, i.e., temperature, precursors, and carrier gas partial pressures. SiGe films with Ge fraction in the 0 to 0.38 range were deposited at temperatures of between 450 and 600 degreesC. The growth rate increases with the partial pressure of the precursors and with the Ge content of the film, except for depositions made with high precursor partial pressure and low Ge fraction. The Ge content of the films increases with the germane fraction in the gas and the partial pressure of the precursors following a nonlinear dependence. The growth process has been analyzed assuming that the controlling reactions are the dissociation of the precursors at the SiGe surface, which are limited by the existence of free sites on the surface, originated by hydrogen desorption from it. The dissociation rate constants of disilane and germane depend on the surface composition and on the respective precursor partial pressure. Films with a Ge fraction lower than 0.5 deposited at temperatures below 500 degreesC are amorphous, but films grown at higher temperatures or with higher Ge fraction are polycrystalline. (C) 2001 The Electrochemical Society.