| Summary: | 碩士 === 國立成功大學 === 電機工程學系碩博士班 === 96 === The aggressive CMOS device scaling has been reaching the physical limit of conventional SiO2 MOSFETs. When the dielectric thickness less than 20Å, the directly tunneling will induce higher leakage current. It is important to find a gate dielectric which could attain most of the merits of SiO2 and high temperature reliability. Essentially, such a candidate should be considered the impact of device characteristics (threshold voltage shift and mobility degradation ) by the charge trap.In this work, we have presented our recent results of HfSiON gate dielectric subjected to various nitridation and PNA treatments. The extracted effective trap density (Nit) of devices are based on charge pumping (CP) measurements. Effect of interface layer (IL) on the electrical characteristics of the HfSiON/IL high-k gate stacks and mobility degradation in nMOSFETs were analyzed and discussed. The IL thickness was found to have a profound effect on the leakage current reduction. The DI-O3 IL has thinner physical thickness than N2O Plasma IL .Since leakage current of the thin dielectric is governed by tunneling mechanism, even the DI-O3 chemical oxide can have better quality oxide interlayer on the Si interface as compared with N2O plasma oxidation interlayer. NH3 plasma can have better dissociation than N2 plasma. But the presence of residual hydrogen coming from NH3 gas has deleterious affects on the charge trapping behaviors of MOSFET devices. After N2 ambient at 850oC for 60s annealing, the N≡N bonds were almost completely eliminated from High-k nitrided film and leaving only strong Si-N bonds. Nitrogen incorporated Hf-silicate dielectric using N2 plasma nitridation with PNA is promising to improve film quality by reducing charge trapping characteristics, improved drain current and enhancing mobility.
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