Investigation of ALD or PVD (Ti-rich vs. N-rich) TiN metal gate thermal stability on HfO2 high-K

The paper reports the impact of TiN metal gate composition (Ti-rich vs. N-rich) and preparation methodology (atomic layer deposition-ALD vs. physical vapor deposition -PVD) on its thermal stability with HfO₂ high-K dielectric, via both physical characterization (X-ray Photoelectron Spectroscopy-XPS, High Resolution TEM combined with Electron Energy Loss Spectroscopy-EELS), and electrical characterization (capacitance voltage -CV & current voltage-IV measurement). After annealing at 1000°C for 30s, it is observed that: 1) Nitrogen tends to out-diffuse from both PVD and ALD TiN; 2) Oxygen from the interfacial layer (IL) between HfO₂ and Si tends to diffuse towards TiN for all the samples. PVD Ti-rich TiN can scavenge more oxygen from IL, but also shows signal of Ti penetration into HfO₂, which poses a concern on its thermal stability; 3) The oxygen out-diffusion from HfO₂/IL stack can be significantly suppressed for ALD TiN compared to the PVD TiN, which is critical to maintain the HfO₂ integrity. The effective work function of TiN metal gate is correlated with its thermal stability.