A Novel Multi Deposition Multi Room-Temperature Annealing Technique via Ultraviolet-Ozone to Improve High-K/Metal (HfZrO/TiN) Gate Stack Integrity for a Gate-Last Process

ALD HfZrO high-K fabricated by novel multi deposition multi annealing (MDMA) technique at room temperature in Ultraviolet-Ozone (UVO) ambient is systematically investigated for the first time via both physical and electrical characterization. As compared to the reference gate stack treated by conventional rapid thermal annealing (RTA) @ 600 degrees C for 30 s (with PVD TiN electrode), the devices receiving MDMA in UVO demonstrates: 1) more than one order of magnitude leakage reduction without EOT penalty at both room temperature and an elevated temperature of 125 degrees C; 2) much improved stress induced degradation in term of leakage increase and flat band voltage shift (both room temperature and 125 degrees C); 3) enhanced dielectrics break-down strength and time-dependant-dielectric-breakdown (TDDB) life time. The improvement strongly correlates with the cycle number of deposition and annealing (D&A, while keeping the total annealing time and total dielectrics thickness as the same). Scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) analysis suggest both oxygen vacancies (V-o) and grain boundaries suppression in the MDMA treated samples are likely responsible for the device improvement. The novel room temperature UVO annealing is promising for the gate stack technology in a gate last integration scheme.