| Oxide semiconductor thin film transistors?TFT?have a widespread potential for in large-size high-definition flat panel displays and complementary metal oxide semiconductors?CMOS?circuits due to the high light transmittance,field-effect mobility,lower process temperature,and large area uniformity.Currently,the stability has become a bottleneck that restricts the commercialization of oxide TFTs.Reducing oxygen vacancies and optimizing the insulator/channel interface are the main means to improve the stability of oxide TFTs.In this paper,the effects of cations?Si and Hf?,anion S doping,and the interface between ALD high ?Zr,Al1-xOy gate insulator and ZnSnO?ZTO?on the stability of ZTO-TFT have been investigated,and the related physics mechanism of stability has also been explored.CMOS devices are also an important application of oxide TFTs.Therefore,seeking the well-matched p-type TFTs and n-type TFTs are the key technologies for constructing high-gain CMOS.In this paper,ultra-high mobility carbon nanotubes are used as the channel layer of p-type transistors to study the effect of high ?AlZrOx gate insulator on the performance of single-walled carbon nanotube?SWCNT?field effect transistors?FET?.Then,the SiZTO-TFT and SWCNT FET have been used to construct a low-power,high-voltage gain CMOS inverter.The main research contents and innovations are as follows:1.Using cationic?Si and Hf?doping to improve the stability of ZTO-TFT.Under the same positive bias stress?PBS?,the threshold voltage?VT?of the ZTO-TFT shifts by?7.5 V,while the VT of the doped HfZTO-TFT and SiZTO-TFT shifts only by?1.2 V and?1.5 V,respectively.Under the same negative bias illumination stress?NBIS?,the VT of the ZTO-TFT shifts by 9 V,whereas the VT of the HfZTO-TFT and SiZTO-TFT shifts only by 1.9 V and 2.6 V,respectively.XPS and capacitance characteristics analysis show that Si and Hf doping can effectively reduce the oxygen vacancies content and the channel/insulator interface defect state density to enhance the stability of ZTO-TFT.2.The novel double-layer structure HfZTO/ZTO-TFT with low oxygen vacancies back channel and high conductivity front channel has been successfully constructed,which solves the contradiction between mobility and stability.The mobility of the double-layer HfZTO/ZTO-TFT is 4 times higher than that of the single-layer HZTO-TFT,and its NBIS and temperature?TS?stability is increased by 56%and 58%compared with the single-layer ZTO-TFT.The carrier concentration of the ZTO front channel layer increases from 2×1015 to 5.6×1017 cm-3,while the oxygen vacancy in the HfZTO back channel layer reduces from 37.05%to 29.81%.Moreover,the density of states?DOS?of the TFT is calculated by the temperature field effect method.Due to the lower defect state density of the HZTO back channel layer,the DOS of HfZTO/ZTO-TFT is reduced by 3×1016 eV/cm3 compared with that of the ZTO-TFT,which proves the reason for the increased stability of the HfZTO/ZTO-TFT.3.A novel low-cost anionic S-doped ZTOS-TFT has been fabricated by co-sputtering,and the effect of S contents on the stability of ZTOS thin films and TFTs is investigated.By S doping,the ZTOS thin film transfers from crystalline into amorphous,and the surface roughness of the thin film decreases from 5.07 nm to 2.02 nm.The amorphous and smooth ZTOS thin film is helpful for large area TFT applications.More importantly,the stability of ZTOS-TFT is significantly improved by S doping.Under the same PBS,NBIS and TS,the shift of VT is reduced by 38%,80%and 76%,respectively.This is mainly due to the suppression of the oxygen vacancies formation by S doping,and the content of oxygen vacancies in the ZTOS film is reduced by 29%,which improves the stability of the ZTOS-TFT.4.In order to meet the requirements of new electronic devices with low power consumption and high stability,the novel ZrxAl1-xOy gete insulator has been constructed to fabricate a low-VT driven,high-stability ZTO-TFT by atomic layer deposition?ALD?.The capacitance of the ZrxAl1-xOy gete insulator increases from 39 to 85 nF/cm2 due to the addition of Zr ions,leading to the decrease of VT from 4.1 to 1.1 V in ZrxAl1-xOy based ZTO-TFT.More importantly,under NBIS and TS,ZTO-TFTs with ZrxAl1-xOy gate insulator f are much more stable than ZTO-TFTs with Al2O3 film as gate insulator.It is known from the temperature field effect method that the diffusion of Zr ions at the ZTO/ZrxAll-xOy interface suppresses the oxygen vacancy in the ZTO channel layer and reduces the density of defect states.It provides a new strategy for manufacturing low-power,high-stability ZTO-TFT.5.For the first time,a solution-processed semiconductor SWCNT FET with a high ? ALD ZrAlOx gate insulator has been realized with the mobility???of 33.3 cm2/Vs,VT of 1.8 V,subthreshold swing?SS?of 0.1 V/dec.and switching ratio(Ion/Ioff)of 8×104.The electrical hysteresis characteristics and negative bias stability of SWCNT FETs are studied.The SWCNT FETs with a ALD ZrAlOx gate insulator shows a very little voltage hysteresis?0.2 V?.Under negative bias stress,the VT shifts only by 2.5 V.The XRD,atomic force microscopy?AFM?and capacitance-frequency?C-f?tests of ZrAlOx insulation layer show that the ALD deposited ZrAlOx insulating layer has an amorphous structure and a smooth surface to reduce interface defect states and improve the property of the SWCNT FET.Therefore,the ALD ZrAlOx gate insulator is the most promising material for the preparation of high-performance SWCNT FET.Moreover,a p-channel SWCNT FET fabricated by solution process and n-channel SiZTO-TFT fabricated by co-sputtering system have been used to construct a low-power,high-gain CMOS inverter.The SiZTO/SWCNT inverter shows excellent performance with a voltage gain of 41.5,a high noise margin of 2.62 V and a low noise margin of 1.86 V at a small VDD of 5 V.The peak consumption is only 3.2×10-8 W at VDD=5 V.Therefore,in terms of integrated circuit applications,low-power,high-gain CMOS inverters with SWCNT FET and SiZTO-TFT has the potential for widespread technological applications. |
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