Impact of Atomic Layer Deposition High k Films on Slow Trap Density in Ge MOS Interfaces With GeOx Interfacial Layers Formed by Plasma Pre-Oxidation

For realizing of Ge complementary metal-oxide-semiconductor with a Ge gate stack with thin equivalent oxide thickness, low interface state density (D
_it
) and high reliability. In this paper, we examine the slow trap behaviors in the ALD high-k materials including Al
₂
O
₃
, Y
₂
O
₃
, HfO
₂
, and La
₂
O
₃
on GeO
_x
/Ge interfaces, where the GeOx interfacial layers are formed by plasma pre-oxidation. The C-V curves, Dit and slow trap density of the high-k/GeO
_x
/nand pGe MOS capacitors are evaluated and compared. The Ge 3d spectra in X-ray photoemission spectroscopy are also compared among the Al
₂
O
₃
, Y
₂
O
₃
, HfO
₂
, and La
₂
O
₃
on GeO
_x
/Ge structures. It is found that Al
₂
O
₃
provides the lowest slow trap density for both electrons and holes in comparison with Y
₂
O
₃
, HfO
₂
, and La
₂
O
₃
high-k films, while similar D
_it
values are observed among the MOS interfaces with Al
₂
O
₃
, Y
₂
O
₃
, HfO
₂
, and La
₂
O
₃
. The additional slow traps in the MOS capacitors with Y
₂
O
₃
, HfO
₂
, and La
₂
O
₃
are attributable to any defects in the high-k films and/or the interfaces with GeO
_x
.