Investigation of ALD or PVD (Ti-rich vs. N-rich) TiN metal gate thermal stability on HfO<inf>2</inf> high-K

Abstract

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 HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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 HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , which poses a concern on its thermal stability; 3) The oxygen out-diffusion from HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /IL stack can be significantly suppressed for ALD TiN compared to the PVD TiN, which is critical to maintain the HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> integrity. The effective work function of TiN metal gate is correlated with its thermal stability.