Abstract
Ultrathin high-
k
Hf
Al
O
x
films on silicon wafers are prepared by pulsed-laser deposition in oxygen-defective ambient. The precipitation of
Hf
O
x
clusters from
Hf
Al
O
x
matrix is revealed by x-ray photoelectron spectroscopy. It is argued that the
Hf
O
x
clusters react with silicon to form Hf-silicide interfacial layer at a temperature as low as
600
°
C
, which evolves into Hf-silicate in the subsequent postannealing at
700
°
C
for
30
s
in oxygen ambient. The optimized fabrication conditions developed to avoid the formation of interfacial layer is employed to prepare high-quality
Hf
Al
O
x
films of excellent electrical characteristics, such as a dielectric constant of 17.7, a small equivalent oxide thickness of
0.66
nm
, a flatband voltage of
0.45
V
, and a low leakage current density of
53.8
mA
∕
cm
2
at
1
V
gate voltage.