RF Characteristics of Room-Temperature-Deposited, Small Gate Dimension Indium Zinc Oxide TFTs

Abstract

Depletion-mode indium zinc oxide channel thin film transistors (TFTs) with gate dimension of 1 X 200 μm and drain-to-source distance of 2.5 μm were fabricated on glass substrates using radio frequency magnetron sputtering deposition at room temperature. Plasma-enhanced chemical vapor deposited SiN x was used as the gate insulator. The threshold voltage was around -2.5 V. Saturation current density at zero gate bias voltage was 2 mA/mm, and a maximum transconductance of 7.5 mS/mm was obtained at V ds = 3 V. The drain current on-to-off ratio was > 10 5 . The maximum field effect mobility measured in the saturation region was ∼ 14.5 cm 2 V -1 s -1 . A unity current gain cutoff frequency, f T , and maximum frequency of oscillation, f max of 180 and 155 MHz, respectively, were obtained. The equivalent device parameters were extracted by fitting the measured s parameters to obtain the intrinsic transconductance, drain resistance, drain-source resistance, transit time, and gate-drain and gate-source capacitance.