CHEMICAL-VAPOR-DEPOSITION OF EPITAXIAL SILICON-GERMANIUM FROM SILANE AND GERMANE .1. KINETICS

We report measured germanium incorporation and growth rate for Si1-xGex grown by very low pressure chemical vapor deposition in the temperature range of 570 to 700 degrees C. The growth rate of Si1-xGex shows different germanium dependencies at different temperatures. We found that the growth rate decreases at 700 degrees C and increases at 570 degrees C with the addition of germanium. The observed nonlinear Arrhenius behavior of the growth rate as a function of germanium content suggests that germanium modifies the activation energy for Si1-xGex deposition, possibly by enhancing hydrogen desorption. The possible rate-limiting steps controlling Si1-xGex deposition were examined by varying the hydrogen flow rate and the total deposition pressure, and it was found that hydrogen suppresses Si1-xGex deposition rate when the germanium content is low. The consistent growth-rate enhancement observed by increasing total deposition pressure is dependent on germanium incorporation and becomes more pronounced as the germanium content is increased. A model is proposed to explain our observations.