Abstract
The impact of thin TaN layers
(
0.5
-
10
nm
)
on the effective work function of polycrystalline silicon (poly-Si)∕TaN stacks has been investigated. It is found that when the TaN layer is as thin as
0.5
nm
, it can have a significant effect on the effective work function of poly-Si, and that
n
-type and
p
-type poly-Si behave differently. The observed results are explained by reactions between poly-Si and the TaN layer leading to the formation of
Ta
x
Si
y
N
z
at the poly-Si-gate dielectric interface. Electrical tests show minimal poly-Si depletion with the TaN layers, and gate leakage current and fixed charges that are comparable to conventional poly-Si electrodes. The results show that these stacked electrodes can be useful for nearly
n
-type effective work functions
(
4.2
-
4.3
eV
)
.