High-performance n-channel 13.56MHz plasma-enhanced chemical vapor deposition nanocrystalline silicon thin-film transistors

Abstract

Hydrogenated nanocrystalline silicon (nc-Si:H) films were directly deposited by using 13.56MHz plasma-enhanced chemical vapor deposition at a substrate temperature of 260°C with highly hydrogen (H2) diluted silane (SiH4) gases. The nc-Si:H film showed a high Raman crystalline volume fraction (XC∼85%) and low oxygen concentration (CO∼1.5×1017at.∕cm3). The formation of high-quality nc-Si:H is explained in terms of the effective roles of atomic hydrogen in the plasma. Top-gate staggered n-channel thin-film transistors (TFTs) adopting 90–100nm nc-Si:H channel and ∼300nm hydrogenated amorphous silicon oxide (a-SiOx) gate dielectric layers showed a field-effect mobility (μFE) of ∼150cm2∕Vs, a threshold voltage (VT) of ∼2V, a subthreshold slope (S) of ∼0.23V∕dec, and an on/off current ratio of more than 106. The TFT performance reported here offers promise for the total integration of peripheral electronics for active-matrix flat panel systems.