Abstract
The fabrication of SiO2-passivated HfO2 (HfO2/SiO2) as a high-k dielectric stack for high-mobility, low-power p-channel SnO thin-film transistors (TFTs) is reported herein. To achieve superior TFT performance, a high-k HfO2 film was introduced by replacing the thermally-grown SiO2. However, the atomic layer deposited (ALD)-SnO films grown on the HfO2 substrate exhibited a very rough surface and out-of-plane tilted SnO (001), resulting in a significantly degraded field-effect mobility (μFE) compared with that of SnO TFTs based on an SiO2 gate dielectric. Therefore, 1–10 nm-thick ALD-SiO2 passivation layers were deposited on high-k HfO2 to effectively improve the surface morphology of the ALD SnO. Furthermore, SiO2 passivation enabled the control of the crystallographic orientation of the ALD SnO. Through SiO2 passivation, the horizontally aligned SnO (00l) planes parallel to the substrate demonstrated significantly improved μFE characteristics. The optimized SnO TFTs fabricated with HfO2/SiO2 stacks exhibited excellent carrier transport and low-voltage operation characteristics, with μFE of 2.3 cm2/V·s, subthreshold swing of 0.5 V/dec, on-to-off drain current ratio of 1.4 × 104, and Vth of −1.2 V.
Published Version
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