Fabrication Craft And Characteristics Analysis Of ZnO Thin Film Transistors

With development of vacuum technology and sputtering coating technology,thin film transistor(TFT)has gradually become key part for display driving circuit because of it's large size,high definition,good light transmission and can use flexible substrate.Based on choice of materials and design of device structure,we fabricate TFT with stacked configuration to reduce length of conductive channel as much as possible.This method improve the operating current of transistor effectively.By using RF magnetron method,sputtering ZnO target to fabricate ZnO thin films on quartz glass substrates.Using AFM to observe the surface morphology and roughness to determine the suitable parameters for thickness of ZnO film.Structure of Al/ZnO/Ni Schottky diode has obvious rectifier characteristics.The turn-on voltage is 2.3V,reverse saturation current is 9.17×10-6A,forward conduction current is milliampere magnitude,devices rectifier ratio is 103,the effective Schottky barrier height is 0.67eV.Fabricate transistor of five layers structure Al/ZnO/Ni/ZnO/Al.The Ni and A1 electrodes were fabricated by DC magnetron sputtering and ZnO active layer using magnetron sputtering.Two layers of A1 were used as drain and source electrode,Ni as the gate electrode,ZnO as active layer.Ni and ZnO is Schottky contact,Al and ZnO is ohmic contact formation.Using Keithley 4200-SCS semiconductor characterization system to analysis zinc oxide thin film transistor which fabricate under different sputtering time conditions and substrate temperature,the operating current can exceed 10mA;When substrate temperature was 340?,device obtained good performance.Increasing sputtering time is beneficial to the formation of the Schottky barrier,but also increasing channel length.Under condition of room temperature,transconductance increases with grid voltage;under condition of 340'C,when VGS<0.4V,transconductance decrease with the gate voltage increase,when VGS>0.4V,transconductance increases with gate voltage increase.Gate voltage can effectively control channel current.Output resistance decrease with drain voltage increas,when drain voltage is less than 1.5V,output resistance drop sharply with the voltage increase,then tends to a certain value.Voltage amplification factor increases with gate voltage increase,and tended to be constant.Through analysis basic electrical properties by experimental data,observe relation between transconductance and gate voltage,output resistance and drain source voltage,voltage amplification ratio and gate voltage of transisitor.Do Calculations to get threshold voltage is 0.45V,which less than horizontal structure thin film transistor.We found carrier is electron,which tunneling inject from the semiconductor layer to Ni electrode.