High quality SiGe epitaxial layer grown by RPCVD using dichlorosilane

The evolution of defect density in non-selective Si/SiGe structures grown with SiH₂Cl₂ as Si source has been studied. High-resolution reciprocal lattice mapping has been performed to characterize the epitaxial quality of the layers. The surface morphology and the density of dislocations were also investigated by using atomic force microscopy. The results showed that a minimum defect density could be obtained for a certain SiH₂Cl ₂ partial pressure. A high partial pressure of SiH₂Cl₂ results in a large amount of Cl-based molecules, which saturates the growth rate. A low partial pressure of SiH₂Cl₂ causes a too low growth rate and the incorporation of impurities in Si lattice increases. Both the above cases lead to a poor epitaxial quality and an optimum value can be obtained in the transit between these two regions in the growth rate vs. SiH₂Cl₂ partial pressure diagram. Applying the optimized SiH₂Cl₂ partial pressure value to grow Si/SiGe layers on the patterned substrate causes a higher defect density than on blanket substrates, which also increases with decreasing the size of the oxide-openings. This is due to injection of the defects from the poly Si/SiGe into the single crystalline region