Study Of Oxide Thin-Film Transistors With Printed Silver Electrodes And Related Researches

With the rapid development of new display technology in ultra-large size and ultra-high definition area,the research of low-cost,high-performance inkjet print devices becomes more important.Inkjet printed silver?Ag?electrode has advantages of high conductivity and low cost,combing with high mobility,low temperature and lagre-area uniform metal oxide semiconductor thin film transistor?MOS-TFT?,could fulfill the urgent needs of display industry about low-cost,low impedance and low signal delay.Hence,for promoting the development of the display insustry,it is of great significance to study MOS-TFT with printed high conductivity Ag electrode.Therefore,from the aspects of material selection,device structures and fabrication processes,the compatibility and interface problems of printed Ag electrode and MOS-TFT have been solved,high-performance MOS-TFT devices with printed Ag electrode have been realized,and the high-definition printing process has been explored.The main researches are shown as follows:?1?The effect of curing processes on the profiles of inkjet printed Ag films was investigated,homogeneous printed Ag films was obtained by utilizing the strong absorption of Ag nanoparticles to ultraviolet.Based on this,we found that the porous structure of the printed Ag electrode would lead to the diffusion of high-energy sputtering insulator particles to the inside of the electrode,resulting in the decrease of the effective thickness of the insulator and the increase of the defect state of the insulator,which would affect the quality of the insulating layer.By introducing a PVP organic layer between gate electrode and semiconductor,the porous structure of printed Ag electrode was repaired,the roughness was decreased,the quality of insulator was ensured.The obtained a-IGZO TFTs with printed Ag gate exhibit a mobility of2.92 cm²V^-1s^-1 and an on/off ratio more than 10⁶.?2?The contact characteristics between the printed Ag nanoparticles electrode and the semiconductor layer was studied.It is found that the organic capping agent of Ag nanoparticles,the solvent erosion and Ag migration induced by annealing process are the main factors which deteriorate the contact characteristic of the metal/semiconductor interface.By optimizing the electrode printing process,Ag nanoparticles have broken the organic capping layer and the obtained a-IGZO TFTs exhibit a mobility of 0.29 cm²V^-1s^-1 and an on/off ratio more than 10⁵.Furthermore,by inserting a layer of water-soluble PVA protection layer between printed electrode and functional layers,the reliability of the semiconductor and the insulation layer are improved,and the Ag migration is restrained.The obtained device exhibits a mobility of 3.36cm²V^-1s^-1,an on/off ratio exceeds 10⁶ and a subthreshold swing of 0.29 V/decades.?3?The contact characteristic between alcohol-based metal organic deposition?MOD?ink and semiconductor layer was studied,it was found less organic residual and less erosion to the semiconductor layer and insulator layer.Ag diffusion is restrained by utilizing low temperature annealing process.The obtained devices exhibit a mobility of 2.01 cm^-2V^-1s^-1,an on/off ratio of 0.4×10⁷,a SS of 1.28 V/decades.Besides,by optimizing the thickness of the semiconductor layer,the contact resistance decreased obviously.When V_G is 10 V,the contact resistance decreased from 4065.3?·m to 81.8?·m.XRR and AFM results showed that the increased roughness enhanced the effective contact.The obtained a-IGZO TFTs device with printed MOD Ag electrodes exhibite a mobility from 2.01 cm²V^-1s^-1 to 6.23 cm²V^-1s^-1,an on/off ratio of6.85×10⁷,a subthreshold swing of 0.37 V/decades.The performance of the device is at the same level to that of the device with sputtered Ag electrodes,which verifies the potential of printed electrode for replacing vacuum electrode.?4?A new depositing process of high-definition electrode was proposed.Aiming at the low precision and line uniformity of drop on demand inkjet printing,we proposed that utilizing of inkjet etching technology could realize the self-assemble distribution of solutes at the edge of inkjet etched holes.Based on Ag nanoparticles ink,the dynamic formation process of Ag nanoparticles rings and short-channels array was studied,and the formation mechanism of the repulsive force between adjacent droplets in inkjet etching process was discussed.It is pointed out that the repulsive force,which prevents the adjacent droplets from merging to each other,is originated from the high evaporation flux at the edge of adjacent droplets and the accumulation of polymer between adjacent droplets.Finally resulted in repeatable and stable Ag nanoparticles rings array and short-channels array,and the width of the channel is only 13?m,the channel length is just 2?m,which provides a new option for improving the accuracy of piezoelectric inkjet printing.