Fabrication and Characterization of Amorphous InGaZnO Thin-Film and Metal-Base Transistors

論文翻譯標題: 非晶態氧化銦鎵鋅薄膜電晶體元件工程開發與垂直式金屬基極電晶體之研製
  • 黃 晧源

學生論文: Doctoral Thesis


Researches on Oxide-semiconductor-based thin-film transistors (TFTs) have advanced remarkably in recent years Commercial display products using indium gallium zinc oxide (InGaZnO) active arrays have also been successfully demonstrated It is highly expected that the oxide semiconductor could have a high potential for use in next-generation display and in system-on-panel application To improve the electrical performance of InGaZnO TFTs various technologies or schemes have been reported to lower driving-voltage enhance carrier mobility reduce leakage current and improve gate control ability In the present dissertation to further polish the performance of InGaZnO TFTs the use of sputtering deposited high-? HfSiO layer as the gate dielectric to enhance the gate control ability of InGaZnO TFTs is demonstrated Sequentially band engineering at source/drain region of the TFT to reduce the leakage current and a post treatment for the channel material using a low thermal budget 248-nm excimer laser annealing to improve the mobility and the current driving ability of the device are proposed and investigated In another aspect high performance vertical InGaZnO metal-base transistors (MBTs) were fabricated successfully by vertically integrating two InGaZnO Schottky diodes Oxygen doping of InGaZnO semiconductor and interlayer insertion between metal and InGaZnO semiconductor were employed to eliminate Fermi level pinning and to enhance Schottky behavior The operation of the InGaZnO MBTs and the improvement of the current gain would be discussed in this dissertation as well Amorphous InGaZnO can be fabricated at room temperature with excellent performance the higher mobility of the material as compared to the amorphous Si has promised the applications in large-scale display and flexible electronics In this dissertation the InGaZnO TFTs were fabricated by sputtering technique firstly Different techniques were used to improve the device performance aim at three different parts of the device including: (1) the gate/gate dielectric/channel stacks (2) the source/drain contact regions and (3) the channel layer In the first part aimming at the gate/gate dielectric/ channel stacks high-? HfSiO gate dielectric were used to fabricate InGaZnO TFTs with a low driving voltage The influence of post-deposition annealing (PDA) temperature in the range of 300-500oC for the HfSiO gate dielectric on device performance was studied In our experiments the 400oC PDA HfSiO/a-InGaZnO TFT exhibits a low threshold voltage of 0 005 V a small subthreshold swing (SS) of 0 11 V/dec a high saturation mobility of 12 7 cm2/Vs and an acceptable current ratio of 3×105 at VD = 1 0 V Next using the high-κ HfSiO as gate dielectric InGaZnO TFTs with a co-sputtered low doping tin indium gallium zinc oxide (SnInGaZnO) electron barrier layer (EBL) were fabricated to enhance the Schottky barrier height and to enlarge the depletion width at the source/drain contact regions By stacking a 250-nm-thick SnInGaZnO EBL at the source/drain region it shows that the turn-off voltage of TFTs increases from -0 5 to about 0 V the on/off current ratio increases from 1 9×105 to 1 9×106 at VD = 1 0 V and the subthreshold swing decreases from 0 13 to 0 073 V/dec while preserving a high mobility and current driving ability as compared to the device without the insertion of source/drain SnInGaZnO electron barrier layers In the third part of this dissertation to adjust the characteristic of sputtering-fabricated InGaZnO channel of TFT without degrading the front-end dielectric film 248-nm KrF excimer laser annealing (ELA) with energy density between 0 and 400 mJ/cm2 were applied and the influence on the electrical behavior of InGaZnO TFTs is investigated The experimental results show that the internal temperature in InGaZnO can be as high as 1000oC the most improved device performance is obtained with high on/off current ratio of 3 5×105 at VD = 1 0 V excellent mobility of 17 8 cm2/Vs and low subthreshold swing of 0 073 V/dec by applying a 300 mJ/cm2 laser pulse In the fourth part of this dissertation InGaZnO TFTs were fabricated by atmospheric pressure plasma jet (APPJ) technique with the advantages including low apparatus cost and better suitability for large-scale and mass production than the sputtering process HfO2 (25 nm) and Al2O3 (25 nm) were used as the gate dielectric stacks NH3 plasma treatment is applied to optimize the device performance by reducing the gate dielectric leakage and increasing the oxide capacitance The best performance of the APPJ InGaZnO TFT is obtained with a 30 W-60 s NH3 plasma treatment with field-effect mobility of 6 1 cm2/Vs which is much higher than the reported InGaZnO TFTs fabricated with solution-process or spray techniques it also shown excellent subthreshold swing of 0 19 V/dec and on/off current ratio of 108 at VD = 1 0 V In the last part of this dissertation in addition to the conventional coplanar TFTs the vertical InGaZnO MBTs were fabricated by integrating the top-contacted Au/HfSiO/InGaZnO and bottom-contacted Ti/InGaZnO Schottky diodes as emitter and collector of the MBT respectively The InGaZnO Schottky diodes (Ti/InGaZnO and Au/HfSiO/InGaZnO) were fabricated through oxygen doping and HfSiO interlayer insertion to eliminate Fermi level pinning and to enhance Schottky behavior attribute to the lowered oxygen vacancies the widened depletion width at the junction and the avoiding of inter-diffusion of the metal cations Different metals (Ti and Au) were chosen for the fabrication of the uni-directional Schottky diodes depending on their reactivity to the oxygen atoms Till now few in-organic materials were reported to use for the fabrication of MBT the high common-emitter current gain (β = 2500) and high common-base current gain (? = 0 9996) obtained from the InGaZnO MBT are much higher than the reported current gains in organic and perovoskite MBTs From the results mentioned above the integration of the high-κ gate dielectric with the InGaZnO semiconductor in both co-planar (TFTs) and vertical device (MBTs) structures have shown excellent electrical performance which could be very promising for application in system-on-panel (SoP) and organic light-emitting (OLED) display in the future
獎項日期2014 八月 16
監督員Shui-Jinn Wang (Supervisor)