Difference Between Atomic Layer Deposition TiAl and Physical Vapor Deposition TiAl in Threshold Voltage Tuning for Metal Gated NMOSFETs
Zhao-Yang Li, Xuejiao Wang, Han-Lun Cai, Zhao-Zhang Yan, Yu-Long Jiang, Jing Wan
Abstract
In this work, the influence of TiAl gate electrode fabricated by atomic layer deposition (ALD) and physical vapor deposition (PVD) on threshold voltage (<inline-formula> <tex-math notation="LaTeX">$\text{V}_{\text {t}}$ </tex-math></inline-formula>) for metal-gated NMOSFETs is respectively investigated. Compared to ALD TiAl, the 200 mV lower <inline-formula> <tex-math notation="LaTeX">$\text{V}_{\text {t}}$ </tex-math></inline-formula> for PVD TiAl is demonstrated and attributed to the oxidation of TiAl with a strong segregation of Ti near TiAl/TaN interface. It is further revealed that by changing the thickness of the first layer ALD TiAl film, the multi-<inline-formula> <tex-math notation="LaTeX">$\text{V}_{\text {t}}$ </tex-math></inline-formula> can be easily obtained within a range of 200 mV using an ALD TiAl /PVD TiAl double layer gate electrode.