Study On The Properties Of SiO_x/SiN_x Gate Insulator And LTPS-TFT Application

With the development of display technology,the performance requirements of display panel for thin film transistors?TFTs?are increasing.However,gate insulator plays an important role in TFTs,thus improving the performance of gate insulator and TFTs is one of the most important issues.Based on the plasma enhanced chemical vapor deposition?PECVD?preparation method,the properties of single-layer films of amorphous silicon oxide?Si O_x?and silicon nitride?Si N_x?,which are used as gate insulator,were studied in this paper.On this basis,the effects of the property changes of Si O_x and Si N_x single-layer films on the performance of Si O_x/Si N_x stacked gate insulator and low-temperature polycrystalline silicon thin film transistors?LTPS-TFTs?were further studied.Firstly,the effects of different process parameters on the properties of single-layer films were investigated.It was found that the compactness of Si O_x increased with the increase of deposition power?650W?2000W?.The reason is that high power can produce strong ion bombardment effect,which makes the structure of the deposited thin film more stable.As for Si N_x,when the nitrogen content was higher than the stoichiometric ratio of Si₃N₄,increasing flow rate of silane?270sccm?500sccm?can reduce the hydrogen content and improve the compactness of the film,where stoichiometric ratio was closer to the Si₃N₄.On the basis of the optimization of Si O_x and Si N_x single-layer films,the study on Si O_x/Si N_xstacked gate insulator was carried out.It was found that depositing at low pressure?750m Torr?1000m Torr?can ensure the densification of the deposited Si O_x and Si N_x,reduce the defects in the stacked gate insulator,and thus improve the breakdown voltage.In addition,increasing the deposition power of Si O_x?900W?2000W?can increase the densification of the film,and reduce the defect content in the film after annealing,which was conducive to improving the dielectric capacity and breakdown characteristics of the stacked gate insulator.The study on the LTPS-TFT devices based on the above-mentioned Si O_x/Si N_x stacked gate insulator showed that by increasing the deposition power of Si O_x and Si N_x?900W?2700W?and increasing silane's flow rate of Si N_x?270sccm?500sccm?,the film compactness was intensified which can effectively reduce|V_th|and S.S.,and thus improved the device performance.Finally,excellent LTPS-TFT device with V_th of-0.16V and S.S.of 0.12V was obtained.