Modification of a polymer gate insulator by zirconium oxide doping for low temperature, high performance indium zinc oxide transistors

Abstract

Indium zinc oxide (IZO) thin film transistors (TFTs) with poly(4-vinylphenol-co-methylmethacrylate) (PVP-co-PMMA) gate insulators were fabricated at a low temperature (250 °C). The bottom gate IZO TFTs with a PVP-co-PMMA gate electric film exhibited inferior device performance to the top gate IZO TFTs, which was attributed to sputtering damage of the underlying polymer gate dielectric film during IZO channel formation. The charge carrier transport and interface properties of the IZO TFTs could be further improved by introducing a ZrO₂ precursor to the polymer gate insulator. The ZrO₂ molecules were well dispersed in the polymer film. The resulting hybrid dielectric film showed a higher capacitance and a smoother morphology than the PVP-co-PMMA dielectric film. The hybrid dielectric-gated IZO TFT had a high mobility of 28.4 cm² V⁻¹ s⁻¹, low subthreshold gate swing of 0.70 V per decade, and a high I_on/off ratio of 4.0 × 10⁷.