In this paper, NH 3 plasma directly applied to the surface of poly-Si channel is studied for the development of high-performance low-temperature polycrystalline-silicon thinfilm transistors (LTPS-TFTs) with HfO 2 high-κ gate dielectric. The reduction of threshold voltage from 1.52 to 0.62 V, the decrease of subthreshold swing from 227 to 151 mV/decade, and the enhancement of field effect mobility μ FE from 31 to 65 cm 2 /V s are observed after NH 3 plasma surface treatment. It can be attributed to the NH 3 plasma surface treatment enabling defect passivation and plasma-induced interfacial layer (PIL) growth. To decouple the impacts of defect passivation and PIL growth, the device without PIL is also fabricated. This paper demonstrates the important impacts of NH 3 plasma surface treatment on the improvement of electrical characteristics of LTPS-TFTs.Index Terms-Interfacial layer, low-temperature polycrystalline-silicon thin-film transistors (LTPS-TFTs), NH 3 , plasma passivation.

Thin gate oxide metal-oxide-semiconductor field-effect transistors with different oxide thickness (180–1000 Å) are fabricated with both the as-grown and etching back methods. In order to segregate the geometrical effect and the growth effect of thin oxides, the surface mobilities of these devices at both room temperature and 77 K are investigated. It is found that the mobility in general decreases with the decrease in gate oxide thickness. The surface mobilities of thin-gate oxide devices fabricated with dual trichloroethylene (TCE) techniques are also studied and it is found that the surface mobility drops with the increase of TCE concentration in the oxidizing ambient. Explanations for these observations based on coulomb scattering and surface roughness scattering mechanisms are suggested.

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