AVS 52nd International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM2-TuM

Paper EM2-TuM3
Fermi Level Pinning at Re/HfO@sub2@ Interface and Effective Work Function of Re in Re/HfO@sub2@/SiO@subx@/n-Si Stack

Tuesday, November 1, 2005, 9:00 am, Room 312

Session: High-k Dielectric Characterization
Presenter: Y. Liang, Freescale Semiconductor Inc.
Authors: Y. Liang, Freescale Semiconductor Inc.
J. Curless, Freescale Semiconductor Inc.
C. Tracy, Freescale Semiconductor Inc.
D. Gilmer, Freescale Semiconductor Inc.
J. Schaeffer, Freescale Semiconductor Inc.
D. Triyoso, Freescale Semiconductor Inc.
P. Tobin, Freescale Semiconductor Inc.
Correspondent: Click to Email
One of the challenges in metal/high-k/Si based CMOS devices is a need for a metal with work function aligned with the Si valence band edge (5.2 eV) for PMOS devices. While a number of metals have vacuum work functions equal or greater than 5.2 eV, their effective work functions in a MOS structure are often less than 5.2 eV due largely to Fermi level pinning in the metal/high-k/Si stack. We used x-ray and ultra-violet photoemission spectroscopy (XPS and UPS) in conjunction with capacitance-voltage (C-V) measurements to investigate Fermi level pinning in a Re/HfO@sub2@/SiO@subx@/n-Si stack. Evolution of the Re vacuum work function at different Re film thickness and the resulting band bending in HfO@sub2@ and Si were determined by in situ XPS and UPS techniques. Results showed that the Re vacuum work function reached a constant value of 5.5 eV when the film exceeded 30 Å thick. Photoemission results further showed that the Fermi level at the Re/HfO@sub2@ interface was partially pinned, resulting in an interface dipole of 0.5 eV and a 5.0 eV effective work function with respect with HfO@sub2@sub. C-V measurement of the Re/HfO@sub2@/SiO@subx@/n-Si stack resulted in a 4.8 eV work function of Re with respect to Si. The difference in work functions determined by photoemission and by C-V will be discussed in terms of the contribution of additional interface dipoles in the Re/HfO@sub2@/SiO@subx@/n-Si stack.