Study Of Si Doping Tin Oxide Thin Film Transistors

Recently,oxide thin film transistors(TFTs)represented by active matrix liquid crystal display(LCD)and active matrix organic light emitting diodes(AMOLED)have significant potential in the flat panel display(FPD)industry.Due to high mobility,good uniformity,high visible light,low cost and low process temperature,the oxide TFT can achieve the technical requirements of large scale,high definition and flexible display.The BCE type device has an advantage of high define accuracy of the channel size over other structures,which can fabricate miniaturized devices to achieve high-resolution display.But its drawback is that the back channel of device is vulnerable to etchants.And it is difficult to obtain high-performance devices.Therefore,it is necessary to develop an acid-resistant oxide semiconductor material.Firstly,Si-doped tin oxide(SnO2?Si,STO)films were deposited by magnetron sputtering.The structure,morphology,composition,optical properties,electrical properties,stress and acid corrosion resistance of STO thin films were studied from the aspects of composition,thickness and annealing temperature of the films.The Si doping content,deposition process and annealing process of STO thin films were optimized.The Si can suppress the crystallization of SnO2 film;the density,optical band gap of film increases and the roughness,defects of film decrease as annealing temperature increases.What is more,the internal stress of film exponentially increases as annealing temperature increases;the STO film has high chemical stability and form a large etching selectivity ratio with Mo.Secondly,this paper fabricated STO-TFT unit devices and optimized the electrical performance.Optimize device performance is optimized from the aspects of composition and thickness of the active layer.The optimized condition of the SiO2 doping content of 5wt% and the active layer thickness of 10 nm,which can make unit device get high performance.At last,we fabricated BCE type STO-TFTs arrays on the pilot line.Impressive transfer characteristic of STO-TFTs was achieved when annealed at 450?,which presents high field-effect mobility of 8.14cm2/V s,turn-on voltage of-1.2V,current on/off of 6.07×109,low sub-threshold swing of 0.21V/decade,as well as low trap density(Dt)of 1.68×1012cm-2eV-1.The device has a good electrical stability.Under the positive bias,the threshold voltage of device drifts 1.15 V forward;at negative bias,the threshold voltage of device drifts-0.64 V negatively.