Investigation And Preparation Of SnO-based P-type Thin Film Transistor

In the field of flat-panel display,thin film transistor(TFT)plays a very important role as the basic unit of pixels.Among them,oxide-based TFT has gradually replaced the traditional amorphous and polycrystalline TFT because of its high mobility,good transparency,excellent uniformity and low processing temperature,and become one of the most promising candidate materials.Although n-type oxide TFT has high device performance and has been used in commercial display applications with the high,p-type oxide TFT with matching performance has rarely been reported.Many potential electronic applications are limited by the lack of high-performance p-type oxide TFT.Therefore,it is of great significance to develop high-performance p-type oxide TFT.To address this issue,several potential materials for realizing p-type devices,such as Cu₂O,NiO,and SnO,have been actively studied.Among them,SnO is the most attractive on account of its comparative advantage in hole mobility performance,which is considered as the key performance.However,the electrical properties of a device are sensitive to the composition of the film and structure of the device.It has always been a difficult problem to stably realize SnO TFT with excellent performance,due to lack of systematic and in-depth research on the internal correlation mechanism between material properties and device performance.Based on this,SnO thin film material was first prepared and optimized in this paper.On the basis of thin film material,effects of deposition condition,annealing process,and device structure on SnO TFT were systematically investigated,and its internal mechanism was also explored.The primary coverage is as follows:1.SnO thin films were prepared by magnetron sputtering,and the influence of oxygen partial pressure(O_PP),annealing atmosphere and annealing temperature on the chemical component and microstructure of the SnO thin films was systematically investigated.The general range of the optimal properties of the film material was as follows:the main component of the film was SnO in range of 0-6.8%;the best crystallization effect and the strongest XRD diffraction peak were achieved at the annealing temperature of 225?;in annealing process,the oxidation degree of SnO film displayed a increasing trend with the increase of the oxygen content in annealing atmosphere.It had laid the groundwork for the subsequent preparation and optimization of SnO TFT.2.Based on the SnO film,the influence of deposition condition and annealing process on the performance of SnO TFT was systematically investigated,and its internal mechanism was also explored.The deposition condition largely consisted of oxygen partial pressure(O_PP),and the annealing process largely consisted of the annealing temperature.SnO TFT exhibited p-type conduction behavior in the range of 4.5-7.5%of the O_PP,and the magnitude of the current displayed a decreasing trend with the increase of O_PP.The amount of Sn and Sn⁴⁺related defect scattering centers were low in this range,leading to the strong hole conduction ability,and SnO TFT exhibited the field-effect mobility of 0.33 cm²V^-1s^-1.The SnO TFT did not exhibit conductive properties if it was prepared at room temperature.With the increase of the annealing temperature increased,the crystal quality of the SnO thin film was improved,and the electrical performance of the SnO TFT was optimized.The optimal modulation effect was achieved at 225?,and the current switching ratio was 889.3.Based on deposition conditions and annealing process optimization of SnO TFT,the effect of device structure on the performance of SnO TFT was systematically investigated.The device structure largely consisted of the thickness of the channel layer and the dielectric layer.Due to the composition of the channel layer and the thickness of the accumulation layer,if the channel layer was too thick or too thin,the device performance would deteriorate.When the channel layer thickness was 45 nm,the SnO TFT exhibited the best performance,and the the current switching ratio was 334.In order to figure out the the problem of large working voltage of SnO TFT,the influence of the thickness of the dielectric layer on the performance of the device was investigated.Compared with the SnO TFT with the dielectric layer of 300 nm SiO₂,the subthreshold gate-source voltage swing of the SnO TFT with the dielectric layer of 50 nm SiO₂ dropped from 25.16Vdec^-1 to 18.5Vdec^-1.At the same time,it was found that the conductive type of the active layer could be changed by the dielectric layer during the course of the study of the high k dielectric layer,which provided a new solution for the preparation of bipolar devices of tin oxide.