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<sub><italic>x</italic></sub>Zr<sub>1–<italic>x</italic></sub>O<sub><italic>y</italic></sub> (0.43 < <italic>x</italic> < 1) gate dielectrics have been investigated. These devices were irradiated by a 662-KeV Cs<inline-formula> <tex-math notation="LaTeX">$^{137} \gamma $ </tex-math></inline-formula>-ray radiation source with 0.5 or –0.5 V gate bias. Prior to irradiation exposure, leakage behavior and bias-instability of Hf<sub><italic>x</italic></sub>Zr<sub>1–<italic>x</italic></sub>O<sub><italic>y</italic></sub> 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<sub>2</sub>, which suggested that the oxygen-vacancy concentration in Hf<sub><italic>x</italic></sub>Zr<sub>1–<italic>x</italic></sub>O<sub><italic>y</italic></sub> was increased by the addition of Zr. Larger flat-band voltage shifts (<inline-formula> <tex-math notation="LaTeX">$\Delta V_{\mathrm {FB}})$ </tex-math></inline-formula> were extracted under positive biased irradiation than the bias only results. The results indicate that radiation-induced interface traps (<inline-formula> <tex-math notation="LaTeX">$\Delta N_{\mathrm {it}})$ </tex-math></inline-formula> are the dominant factor for <inline-formula> <tex-math notation="LaTeX">$\Delta V_{\mathrm {FB}}$ </tex-math></inline-formula> in HfO<sub>2</sub> thin films, whereas the radiation response for Zr-containing dielectrics under PB was mainly due to oxide traps. Under negative biased irradiation, <inline-formula> <tex-math notation="LaTeX">$\Delta V_{\mathrm {FB}}$ </tex-math></inline-formula> 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<sub><italic>x</italic></sub>Zr<sub>1–<italic>x</italic></sub>O<sub><italic>y</italic></sub> at each dose level. Hf<sub><italic>x</italic></sub>Zr<sub>1–<italic>x</italic></sub>O<sub><italic>y</italic></sub> is identified as a promising gate dielectric for advanced complementary metal–oxide–semiconductor technologies.

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