Title :
Characteristics and mechanism of tunable work function gate electrodes using a bilayer metal structure on SiO2 and HfO2
Author :
Lu, Ching-Huang ; Wong, Gloria M.T. ; Deal, Michael D. ; Tsai, Wilman ; Majh, Prashant ; Chui, Chi On ; Visokay, Mark R. ; Chambers, James J. ; Colombo, Luigi ; Clemens, Bruce M. ; Nishi, Yoshio
Author_Institution :
Dept. of Mater. Sci. & Eng., Stanford Univ., CA, USA
fDate :
7/1/2005 12:00:00 AM
Abstract :
In this letter, we investigate a method to adjust the gate work function of an MOS structure by stacking two metals with different work functions. This method can provide work function tunability of approximately 1 eV as the bottom metal layer thickness is increased from 0 to about 10 nm. This behavior is demonstrated with different metal combinations on both SiO2 and HfO2 gate dielectrics. We use capacitance-voltage (C-V) characteristics to investigate the effect of different annealing conditions and different metal/metal bilayer couples on the work function. By comparing the as-deposited and annealed films, and by comparing with metals that are relatively inert with each other, we deduce that the work function tuning behavior likely involves metal/metal interdiffusion.
Keywords :
MIS devices; annealing; dielectric thin films; hafnium compounds; metal-insulator boundaries; silicon compounds; work function; HfO2; MOS structure; SiO2; annealed films; annealing conditions; as-deposited films; bilayer metal structure; capacitance-voltage characteristics; gate dielectrics; high-k dielectrics; metal combinations; metal layer thickness; metal/metal bilayer couples; metal/metal interdiffusion; tunable work function gate electrodes; Annealing; CMOS technology; Capacitance; Dielectric thin films; Electrodes; Hafnium oxide; Materials science and technology; Plasma temperature; Stacking; Threshold voltage; high-; metal gate; work function;
Journal_Title :
Electron Device Letters, IEEE
DOI :
10.1109/LED.2005.851232
