Difference Between Atomic Layer Deposition TiAl and Physical Vapor Deposition TiAl in Threshold Voltage Tuning for Metal Gated NMOSFETs

• Published in: IEEE electron device letters Vol. 42; no. 12; pp. 1830 - 1833
• Main Authors: Li, Zhao-Yang, Wang, Xue-Jiao, Cai, Han-Lun, Yan, Zhao-Zhang, Jiang, Yu-Long, Wan, Jing
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.12.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: ALD; Atomic layer epitaxy; effective work function; Intermetallic compounds; Logic gates; Metals; MOSFET; MOSFETs; Oxidation; Physical vapor deposition; PVD; Thickness; Threshold voltage; TiAl; Tin; Titanium aluminides; Tuning
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2021.3124801

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.