Defect reduction for formation of epitaxial layer in source and drain regions

A method of growing an epitaxial layer, comprising:

• forming a gate structure over a substrate;
• removing portions of the substrate to form recesses adjacent to the gate structure;
• removing a native oxide layer formed on surfaces of the recesses with a controlled over-etch amount;
• performing a pre-deposition clean to remove particles on surfaces of the recesses after removing the native oxide layer;
• and
• performing an asymmetric cyclic deposition and etching (CDE) process to form the epitaxial layer, wherein initial CDE unit cycles have a lower etch to deposition ratio than remaining CDE unit cycles, and wherein the removing a native oxide layer, the performing a pre-deposition clean, and the performing an asymmetric CDE process are performed in an integrated system without exposing the substrate to air after the native oxide layer is removed.

A method of growing an epitaxial layer, comprising:

• forming a gate structure over a substrate;
• etching recesses in the substrate adjacent to the gate structure;
• removing a native oxide layer formed on surfaces of the recesses with a controlled over-etch amount;
• performing a pre-deposition clean to remove particles on the surfaces of the recesses after removing the native oxide layer, wherein a total number of particles remaining in the recesses after performing the pre-deposition clean is less than about 3 in a die;
• and
• performing an asymmetric cyclic deposition and etching (CDE) process to form the epitaxial layer, wherein initial CDE unit cycles have a lower etch to deposition ratio than remaining CDE unit cycles.