Total Dose Effects and Bias Instabilities of (NH4)2S Passivated Ge MOS Capacitors With HfxZr1–xOy Thin Films

The effects of biased irradiation on Ge MOS capacitors with Hf
_x
Zr
_1-x
O
_y
(0.43 <; x <; 1) gate dielectrics have been investigated. These devices were irradiated by a 662-KeV Cs
¹³⁷
γ-ray radiation source with 0.5 or -0.5 V gate bias. Prior to irradiation exposure, leakage behavior and bias-instability of Hf
_x
Zr
_1-x
O
_y
films were also examined. Gate leakage current density increases with the increasing of Zr composition in gate oxide. In addition, Zr-containing dielectrics under positive bias (PB) exhibited more oxide negative trapped charges than that of HfO
₂
, which suggested that the oxygen-vacancy concentration in Hf
_x
Zr
_1-x
O
_y
was increased by the addition of Zr. Larger flat-band voltage shifts (AVFB) were extracted under positive biased irradiation than the bias only results. The results indicate that radiation-induced interface traps (ΔN
_it
) are the dominant factor for ΔV
_FB
in HfO
₂
thin films, whereas the radiation response for Zr-containing dielectrics under PB was mainly due to oxide traps. Under negative biased irradiation, ΔV
_FB
was attributed to the combined effect of the net oxide trapped charges and the passivation of Ge dangling bonds at the Ge/high-k interface. Additionally, both bias-induced and radiation-induced charge trapping have a crucial effect on radiation response of Hf
_x
Zr
_1-x
O
_y
at each dose level. Hf
_x
Zr
_1-x
O
_y
is identified as a promising gate dielectric for advanced complementary metal-oxide-semiconductor technologies.