Total Dose Effects and Bias Instabilities of (NH4)2S Passivated Ge MOS Capacitors With Hf<italic>x</italic>Zr1–<italic>x</italic>O<italic>y</italic>Thin Films

Abstract

The effects of biased irradiation on Ge MOS capacitors with Hf x Zr1– x O y (0.43 x $^{137} \gamma $ -ray radiation source with 0.5 or –0.5 V gate bias. Prior to irradiation exposure, leakage behavior and bias-instability of Hf x Zr1– 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 HfO2, which suggested that the oxygen-vacancy concentration in Hf x Zr1– x O y was increased by the addition of Zr. Larger flat-band voltage shifts ( $\Delta V_{\mathrm {FB}})$ were extracted under positive biased irradiation than the bias only results. The results indicate that radiation-induced interface traps ( $\Delta N_{\mathrm {it}})$ are the dominant factor for $\Delta V_{\mathrm {FB}}$ in HfO2 thin films, whereas the radiation response for Zr-containing dielectrics under PB was mainly due to oxide traps. Under negative biased irradiation, $\Delta V_{\mathrm {FB}}$ 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 Zr1– x O y at each dose level. Hf x Zr1– x O y is identified as a promising gate dielectric for advanced complementary metal–oxide–semiconductor technologies.