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°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°C; 2) much improved stress induced degradation in term of leakage increase and flat band voltage shift (both room temperature and 125°C); 3) enhanced dielectrics break-down strength and time-dependent-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.