| The goal of this dissertation is to develop high performance indium gallium zinc oxide (IGZO) based thin film transistors and circuits. Individual IGZO transistors on glass and silicon were optimized and used to form basic circuit elements including inverters, NOR and NAND gates. A novel focused ion beam (FIB) approach was also investigated, where devices were formed by milling a channel to separate the source and drain. This first report of forming IGZO transistors by focused ion beam milling with sub-micron channels is interesting since it sidesteps having to use e-beam lithography or advanced photolithography methods.;Typical IGZO TFTs on glass with an AlOx gate dielectric, at VDS = 5 V, a threshold voltage of 0.2 V, a subthreshold slope of less than 190 mV/decade, an on/off current ratio larger than 108, and a saturation field effect mobility musat of 14 cm2 V -1 S-1 were measured.;IGZO based logic gates including inverter, NAND and NOR gates were designed, fabricated and characterized. For a typical inverter, a peak gain magnitude of 18.4 was measured at VDD=20V for static characterization. The transfer characteristics of logic gates under different supply voltages with a variety of beta ratios were also discussed and analyzed. The NAND and NOR gates demonstrated sharp transfer characteristics and satisfactory functionality between 1 and 20 V with operating frequencies reaching 5 kHz.;Submicron IGZO TFTs formed using focused ion beam etching were successfully fabricated and demonstrated. Typical devices were fabricated on SiO2 /Si substrate with a bottom gate structure. Devices with channel lengths as small as 50 nm were obtained. The devices were unusual in that a side gate channel was formed. Optimized devices had on/off ratio of 108, a threshold voltage of 0.2V and subthreshold slope of 170mV/decade were measured.;IGZO is a fascinating material with high potential to be used in a wide variety of technologies. Applications include future high-end displays, transparent electronics, flexible electronics, memories, and potentially three dimensional integrated circuits. |
