NMOS Epitaxy - Defect Free and Low Resistivity Films

摘要

Selective Epitaxy technology with phosphorous and/or carbon addition for advanced nMOS has several advantages - to enhance tensile stress, lower series resistance, and block the diffusion of phosphorous [1][2][3]. pMOS strained SiGe process is now mainstream and well characterized. However, the nMOS Epitaxy process has several challenging process requirements, especially related to resistivity (with/without Carbon), film selectivity, and defect control. Lower film deposition temperatures can help reduce film resistivity, however, selectivity, defectivity, and growth rates are compromised. Cyclic deposition and etch processes are typically required to recover film selectivity and growth rates. Cyclic process contains a non-selective deposition step to optimize the film resistivity/carbon concentration and an etch step to optimize morphology and selectivity. Various process parameters are explored in this paper to achieve in-situ phosphorus doped selective Epi with low resistivity and defect free microstructure.