Asymmetric Cyclic Deposition and Etch Process for Epitaxial Formation Mechanisms of Source and Drain Regions

A method comprising:

• forming a gate structure over a substrate;
• removing a portion of the substrate to form a recess adjacent to the gate structure;
• and
• depositing a first epitaxial layer in the recess, wherein depositing the first epitaxial layer uses an asymmetric cyclic deposition and etching (ACDE) process, wherein the ACDE process includes a first CDE unit cycle (CDE-1) and a following CDE unit cycle (CDE-i), wherein the CDE-1 and the CDE-i are different, wherein the CDE-i is repeated one or more times, and wherein each deposition process of the ACDE process is separated from any etch process of the ACDE process by at least one purge process.

A method of forming an integrated circuit, the method comprising:

• forming a gate structure over a substrate;
• removing a portion of the substrate to form a recess adjacent to the gate structure;
• depositing a first epitaxial layer in the recesses, wherein depositing the first epitaxial layer uses an asymmetric cyclic deposition and etching (ACDE) process, wherein the ACDE process includes a plurality of CDE unit cycles, and wherein each etch process of each CDE unit cycle follows at least one deposition process of a corresponding CDE unit cycle;
• and
• after depositing the first epitaxial layer, depositing a second epitaxial layer in the recess by performing a selective epitaxial growth (SEG) process, wherein the SEG process involves simultaneous deposition and etch.