Effects of HCl on the Growth of Epitaxial Ge

The goal of this work is to understand and optimize growth conditions to effectively grow Ge in oxide trenches of varying widths and depths. The oxide trenches are patterned on a Si wafer leaving areas of exposed Si, from which a SiGe seed layer is grown, followed by a Ge growth to fill the oxide trench. The intention is to SEG the Ge to an overfilled level in the oxide trench. To establish a Ge SEG process, the method of using a selective high Ge concentration (60-70%) SiGe seed layer to a thickness greater than its critical thickness for the stated concentration allows for the film to be relaxed when the Ge is grown. The presence of the relaxed SiGe seed reduces the nucleation delay and defects during the Ge growth. Kim’s reported work on nucleation density of Ge on oxide over a range of temperatures and pressures is a good starting point [1]. However, in replicating stated conditions of 600C at 15T, gross nucleation on the oxide surface is observed (Fig. 1(a)). The nucleation can be a result of many factors, a few being; surface preparations prior to SEG (pre-cleans), or the presence of the selective high Ge concentration SiGe seed layer that is leaving nucleation sites on the oxide, or the overall exposed Si surface area, otherwise known as a loading effect.