Abstract
The effect of Si concentration on the effective work function of tantalum silicon (Ta-Si) alloy systems as gate electrodes in direct contact with
Si
O
2
and
Hf
Si
O
x
gate dielectrics has been studied extensively. It was found that the Si concentration in the Ta-Si electrodes (
⩾
60
at.
%
Si) has a strong effect on the effective work function, and three discrete composition-dependent phases (tantalum metal, tantalum silicide, and silicon) coexist in the films. The film resistivity and density also change dramatically as a function of Si concentration. Physical analysis shows that these Si-rich Ta-Si electrodes are amorphous at room temperature and crystallize with a
1000
°
C
,
5
-
s
anneal. Finally, an effective work function value of
3.98
eV
has been achieved by arsenic implantation of a capacitor electrode layer in
Ta
-
Si
∕
Hf
Si
O
x
film systems, thereby producing a potential
n
-type metal gate electrode in conjunction with high-
k
gate dielectrics.