Low-temperature sol-gel ZrHfO2-PMMA hybrid dielectric thin-films for metal oxide TFTs

Abstract

In this work, we developed a novel inorganic-organic hybrid gate dielectric by combining zirconium and hafnium components to form zirconium hafnium oxide strongly linked with polymethyl methacrylate (ZrHfO2-PMMA) and deposited at low temperature (200 °C) by sol-gel method. The obtained 108 nm thick, high-quality hybrid gate dielectric showed an exceptionally low surface roughness (0.9-nm), a low leakage current density (7.7 × 10−6 A/cm2) and reasonable dielectric properties such as gate capacitance along with dielectric constant (77 nF/cm2 & 9.4 @1 kHz) respectively. To examine the ZrHfO2-PMMA hybrid dielectric electrical properties we constructed thin-film transistors (TFTs) with room temperature r.f sputtered n-type metal oxide semiconductors, a-IGZO and ZnO, as active channels. The bottom gate fabricated a-IGZO TFTs driving at as low as below 6 V, with extracted field effect mobility of 2.45 cm2/V. s, a low threshold voltage of 1.2 V with large ON/OFF current ratio 107 respectively. On the other hand, for comparison we employed ZnO TFTs by applying same hybrid dielectric system, the obtained parameters of bottom gate ZnO TFTs were good field effect saturation mobility of 12.8 cm2/V. s, threshold voltage of 1.8 V and ON/OFF current ratio of 103.