Research On Deposition And Performance Of Graded-channel Metal Oxide Thin Film Transistor

In a future influenced by the Internet of Things(Io T),artificial intelligence,smart assistance systems,supportive electronics collecting and processing data will be present in nearly all facets of our society.Thin film transistors(TFT)are used as driving units in these devices and need to have high on/off current ratios,mobility,and small sub-threshold swings.IGZO is the current mainstream thin film transistor material,but it is difficult to achieve both transport performance and stability.This article will solve this problem by the following parts.In ultra-high vacuum,radio frequency magnetron sputtering was used to deposite IGZO films with different contents of nitrogen,and a series of characterizations were performed on them.The results suggested that The light transmittance in the visible light region of IGZO films prepared with different process parameters is larger than 80%;XPS results showed that the oxygen vacancy content in the IGZO film increases with the increase of the nitrogen doping content,and then increases.The oxygen vacancy reached a minimum value of about 11%at a nitrogen flow rate of 0.4 sccm,and then reached 30%at 0.6 sccm.Next,this article explores the effect of annealing and passivation on the performance of TFT.The structure used in this article is a bottom-gate top-contact structure.The channel and source and drain dimensions are precisely defined by photolithography.The effect of different annealing temperatures on IGZO thin film transistor is studied.The influence of zinc oxide thin film transistor performance,the IGZO thin film transistor has excellent performance when the temperature of annealing is 400?.In addition,the influence of the passivation layer and whether annealing before and after passivation on the performance of IGZO thin film transistor is explored.It can be concluded that the IGZO thin film transistor is annealed before passivation,and the second annealing is performed after the passivation.After annealing,a thin film transistor with excellent performance can be obtained.In addition,passivation can greatly improve the stability of TFT.Then we investigate the transport performance and stability of IGZO TFT with different nitrogen content.It is concluded that when the nitrogen flow rate is 0.4sccm,the transport performance is better,and the saturation mobility is 6.61cm²/Vs,The sub-threshold swing(SS)180m V/dec,and the I_on/I_offis 2×10⁸.And the stability is improved compared to the thin film transistor without nitrogen doping.In the 3h positive bias stability and negative bias light stability test,the threshold voltage shift is+0.26V and-0.83V,respectively;Then in order to reduce the deterioration of the transport performance of the thin film transistor by nitrogen doping,only a certain thickness of nitrogen is doped in the back channel of the thin film transistor.The effect of the back channel doping with different thickness of nitrogen on the performance of indium gallium zinc oxide TFT is explored.The results show that when the nitrogen doping time at the back channel is 60nm,the?_satis 7.61cm²/Vs,the I_on/I_offis 8×10^-8,the threshold voltage is-1.4V,and the SS is 162.602m V/decade.In the 3h positive bias voltage stability test and negative bias voltage light stability test,the threshold voltage shift was+0.43V and-0.83V,respectively.In order to improve its transport performance,an ultra-thin high-carrier layer was introduced in the front channel by oxygen co-doping,and the effect of the thickness of the high-carrier layer on the performance of IGZO thin-film transistors was explored.The I_offincreased with the increase of the thickness of the high-carrier layer,and the transport performance is the best when the thickness of the high-carrier layer is 2nm.Finally,a three-graded channel IGZO thin film transistor was prepared,and the excellent performance of SS?137 m V/dec,I_on/I_off?2×10⁹,V_TH?0.34V,and?_sat?34.64 cm²/Vs was obtained.In the 3h positive bias voltage stability test and negative bias voltage light stability test,the threshold voltage shift was+0.4V and-0.8V,respectively.