Title :
Fermi-level pinning induced thermal instability in the effective work function of TaN in TaN/SiO2 gate stack
Author :
Ren, C. ; Yu, H.Y. ; Kang, J.F. ; Hou, Y.T. ; Li, M.-F. ; Wang, W.D. ; Chan, D.S.H. ; Kwong, D.-L.
Author_Institution :
Dept. of Electr. & Comput. Eng., Nat. Univ. of Singapore, Singapore
fDate :
3/1/2004 12:00:00 AM
Abstract :
In this letter, we demonstrate for the first time that the Fermi-level pinning caused by the formation of Ta(N)-Si bonds at the TaN/SiO2 interface is responsible for the thermal instability of the effective work function of TaN in TaN/SiO2 devices after high temperature rapid thermal annealing (RTA). Because of weak charge transfer between Hf and Ta(N) and hence negligible pinning effect at the TaN/HfO2 interface, the effective work function of TaN is significantly more thermally stable on HfO2 than on SiO2 dielectric during RTA. This finding provides a guideline for the work function tuning and the integration of metal gate with high-κ dielectric for advanced CMOS devices.
Keywords :
CMOS integrated circuits; Fermi level; MIS devices; interface states; nitrogen compounds; oxygen compounds; rapid thermal annealing; semiconductor thin films; silicon compounds; tantalum compounds; thermal stability; wide band gap semiconductors; work function; Fermi-level pinning; Hf; TaN-SiO2; advanced CMOS devices; charge transfer; gate stack; high-k dielectric; interface; rapid thermal annealing; thermal instability; work function; Chemical vapor deposition; Dielectric materials; Dielectric substrates; Electrodes; Hafnium oxide; MOS capacitors; MOS devices; Rapid thermal annealing; Silicon; Temperature;
Journal_Title :
Electron Device Letters, IEEE
DOI :
10.1109/LED.2004.824251
