Mobility Enhancement Induced by Oxygen Gettering of TiAl for Metal Gated NMOSFETs

• Published in: IEEE transactions on electron devices Vol. 70; no. 3; pp. 871 - 876
• Main Authors: Li, Zhao-Yang, Wang, Xue-Jiao, Cai, Han-Lun, Yan, Zhao-Zhang, Huang, Tao, Jiang, Yu-Long, Wan, Jing
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.03.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 1/f noise; Atomic layer epitaxy; Bulk density; Dielectric strength; Dielectrics; Electron mobility; Gettering; Hafnium oxide; Intermetallic compounds; Logic gates; Metals; Mobility; MOSFET; MOSFETs; oxygen gettering; Photoelectrons; Physical vapor deposition; Scattering; TiAl; Titanium aluminides; Trapping; X ray photoelectron spectroscopy; X-ray spectroscopy
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2023.3235315

In this work, the influence of TiAl gate electrodes fabricated by physical vapor deposition (PVD) and atomic layer deposition (ALD) on electron mobility for metal-gated NMOSFETs is respectively investigated. Due to the specific production chemistry, the ALD TiAl film inherently contains lots of C atoms, which further suppresses its O-gettering capability. Compared to the ALD TiAl device, about 15% higher peak mobility for the PVD TiAl device is demonstrated, which is attributed to the lower bulk trap density in gate dielectric layers as revealed by the 1/<inline-formula> <tex-math notation="LaTeX">{f} </tex-math></inline-formula> noise characteristics analysis. By means of the energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) analysis, the reduced trap density is related to the fact that PVD TiAl can extract more O atoms from gate dielectric layers than ALD TiAl, which weakens the electron trapping/de-trapping process and correspondingly enhances the mobility.