Research On Low-temperature Giant-dielectric Thin Films And Their Thin-film Transistors

Thin-film transistors?TFT?are widely used in display fields such as active matrix liquid crystal display?AMLCD?and active matrix light emitting diodes?AMOLED?.Low-voltage TFT has become a very hot research topic in the field of low-power TFT.Oxide TFT has been widely used in high resolution and large-size display,due to the advantages of large area uniformity and low cost.Therefore,the thesis focuses on the field of low-voltage oxide TFT.First,it is invented to use"the giant dielectric thin film material"as the gate dielectric layer of TFT?abbreviation of this type TFT is"giant dielectric TFT"?.Compared with the low-voltage TFT devices?ferroelectric TFT,electric double layer TFT,etc.?reported in the current literature,this giant dielectric TFT device has greater advantages in sub-threshold swing?SS?,operating voltage(V_op),positive and negative sweep hysteresis?|?Vhys|?,operating frequency and other device performance indicators.Second,the In_0.0025Nb_0.0025Ti_0.995O₂ giant dielectric thin film and its TFT device have been realized at low temperature?400 ??by the RF magnetron sputtering method.The quasi-static capacitance density?C_i?of the film is 36156 n F/cm²,and the C_i is 7607 n F/cm² at 1 k Hz.At the same time,the carrier mobility???of the TFT device is 1.9 cm²V^-1s^-1,the threshold voltage(V_TH)is 0.35 V,the SS is 68 m V/dec,and the V_op is 1 V?the drive current I_D is up to 45?A at this voltage?,the|?Vhys|is 0.016 V.Third,the Sm_0.0025Nb_0.0025Ti_0.995O₂ giant dielectric thin film and its TFT device have been realized at low temperature?300 ??by the DC reactive sputtering method,to solve the problems of slow growth rate,low film density,poor frequency response,and excessive leakage current of In_0.0025Nb_0.0025Ti_0.995O₂ prepared by RF magnetron sputtering method.The quasi-static C_i of the film is 1850 n F/cm²,and the C_i is 1302 n F/cm² at 1 k Hz.The frequency response of the film is much higher than the In_0.0025Nb_0.0025Ti_0.995O₂ film prepared by the RF magnetron sputtering method.The reason might be that the Sm-O bond in the film is stronger than the In-O bond,reducing the concentration of the oxygen vacancies.And,fewer oxygen vacancies result in fewer electrons ionized by the oxygen vacancies,thereby reducing the leakage conduction losses when the film is polarized.In addition,the film prepared by the DC reactive sputtering method has a lower porosity than the RF sputtering method,so the leakage conduction loss is less when the film is polarized.At the same time,the?of the TFT device is2.9 cm²V^-1s^-1,the V_TH is-0.20 V,the SS is 92 m V/dec,the V_op is 1 V?the I_D is 20?A at this voltage?,and the|?Vhys|is 0.110 V.Last,the Sm_0.0025Nb_0.0025T_i0.995O₂ giant dielectric thin film and its TFT device have been realized at low temperature?300 ??by the solution method to further reduce the manufacturing cost.The quasi-static C_i of the film is 2200 n F/cm²,and the C_i is 344 n F/cm² at 1 k Hz.The frequency response of the film is significantly lower than the Sm_0.0025Nb_0.0025T_i0.995O₂ film prepared by DC reactive sputtering.The reason might be that the Sm_0.0025Nb_0.0025Ti_0.995O₂ thin film prepared by the solution method has a large amount of residual defects C,H and other defects,which cannot contribute to the dielectric response at high frequencies.As a result,the dielectric property of the film is reduced at high frequencies.