Crystallization of amorphous silicon(a-Si) which starts from the middle of the a-Si region separating two adjacent metal-induced crystallization(MIC) polycrystalline silicon(poly-Si) regions is observed. The cry...Crystallization of amorphous silicon(a-Si) which starts from the middle of the a-Si region separating two adjacent metal-induced crystallization(MIC) polycrystalline silicon(poly-Si) regions is observed. The crystallization is found to be related to the distance between the neighboring nickel-introducing MIC windows. Trace nickel that diffuses from the MIC window into the a-Si matrix during the MIC heat-treatment is experimentally discovered, which is responsible for the crystallization of the a-Si beyond the MIC front. A minimum diffusion coefficient of 1.84×10^-9cm^2/s at 550℃ is estimated for the trace nickel diffusion in a-Si.展开更多
A new type of degradation phenomena featured with increased subthreshold swing and threshold voltage after negative gate bias stress(NBS)is observed for amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs),which can r...A new type of degradation phenomena featured with increased subthreshold swing and threshold voltage after negative gate bias stress(NBS)is observed for amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs),which can recover in a short time.After comparing with the degradation phenomena under negative bias illumination stress(NBIS),positive bias stress(PBS),and positive bias illumination stress(PBIS),degradation mechanisms under NBS is proposed to be the generation of singly charged oxygen vacancies(V_(o)^(+))in addition to the commonly reported doubly charged oxygen vacancies(V_(o)^(2+)).Furthermore,the NBS degradation phenomena can only be observed when the transfer curves after NBS are measured from the negative gate bias to the positive gate bias direction due to the fast recovery of V_(o)^(+)under positive gate bias.The proposed degradation mechanisms are verified by TCAD simulation.展开更多
The negative gate bias stress(NBS)reliability of n-type polycrystalline silicon(poly-Si)thin-film transistors(TFTs)with a distinct defective grain boundary(GB)in the channel is investigated.Results show that conventio...The negative gate bias stress(NBS)reliability of n-type polycrystalline silicon(poly-Si)thin-film transistors(TFTs)with a distinct defective grain boundary(GB)in the channel is investigated.Results show that conventional NBS degradation with negative shift of the transfer curves is absent.The on-state current is decreased,but the subthreshold characteristics are not affected.The gate bias dependence of the drain leakage current at V_(ds)of 5.0 V is suppressed,whereas the drain leakage current at V_(ds)of 0.1 V exhibits obvious gate bias dependence.As confirmed via TCAD simulation,the corresponding mechanisms are proposed to be trap state generation in the GB region,positive-charge local formation in the gate oxide near the source and drain,and trap state introduction in the gate oxide.展开更多
Persistent photoconductivity(PPC)effect and its light-intensity dependence of both enhancement and depletion(E-/D-)mode amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs)are systematically investigated.Density of ox...Persistent photoconductivity(PPC)effect and its light-intensity dependence of both enhancement and depletion(E-/D-)mode amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs)are systematically investigated.Density of oxygen vacancy(V O)defects of E-mode TFTs is relatively small,in which formation of the photo-induced metastable defects is thermally activated,and the activation energy(E a)decreases continuously with increasing light-intensity.Density of V O defects of D-mode TFTs is much larger,in which the formation of photo-induced metastable defects is found to be spontaneous instead of thermally activated.Furthermore,for the first time it is found that a threshold dose of light-exposure is required to form fully developed photo-induced metastable defects.Under low light-exposure below the threshold,only a low PPC barrier is formed and the PPC recovery is fast.With increasing the light-exposure to the threshold,the lattice relaxation of metal cations adjacent to the doubly ionized oxygen vacancies(V O^2+)is fully developed,and the PPC barrier increases to∼0.25 eV,which remains basically unchanged under higher light-exposure.Based on the density of V O defects in the channel and the condition of light illumination,a unified model of formation of photo-induced metastable defects in a-IGZO TFTs is proposed to explain the experimental observations.展开更多
Degradation of a-InGaZnO thin-film transistors working under simultaneous DC gate and drain bias stress is investigated,and the corresponding degradation mechanism is proposed and verified.The maximum degradation occu...Degradation of a-InGaZnO thin-film transistors working under simultaneous DC gate and drain bias stress is investigated,and the corresponding degradation mechanism is proposed and verified.The maximum degradation occurs under the bias stress condition that makes the electric field and electron concentration relatively high at the same time.Trapping of hot electrons in the etching-stop layer under the extended drain electrode is proven to be the underlying mechanism.The observed degradation phenomena,including distortion in the transfer curve on a logarithmic scale and two-slope dependence on gate bias on a linear scale,current crowding in the output curve,and smaller degradation in transfer curves measured under large drain bias,can all be well explained with the proposed degradation mechanism.展开更多
The temperature distribution of typical n-type polycrystalline silicon thin film transistors under selfheating(SH)stress is studied by finite element analysis.From both steady-state and transient thermal simulation,th...The temperature distribution of typical n-type polycrystalline silicon thin film transistors under selfheating(SH)stress is studied by finite element analysis.From both steady-state and transient thermal simulation,the influence of device power density,substrate material,and channel width on device temperature distribution is analyzed.This study is helpful to understand the mechanism of SH degradation,and to effectively alleviate the SH effect in device operation.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.61301077 and 61574096)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20130319)the Science and Technology Program of Suzhou City,China(Grant No.SYG201538)
文摘Crystallization of amorphous silicon(a-Si) which starts from the middle of the a-Si region separating two adjacent metal-induced crystallization(MIC) polycrystalline silicon(poly-Si) regions is observed. The crystallization is found to be related to the distance between the neighboring nickel-introducing MIC windows. Trace nickel that diffuses from the MIC window into the a-Si matrix during the MIC heat-treatment is experimentally discovered, which is responsible for the crystallization of the a-Si beyond the MIC front. A minimum diffusion coefficient of 1.84×10^-9cm^2/s at 550℃ is estimated for the trace nickel diffusion in a-Si.
基金Project supported in part by the National Natural Science Foundation of China(Grant Nos.61971299 and 61974101)the Natural Science Foundation of Jiangsu Province,China(Grant No.SBK2020021406)+2 种基金the Fund from the State Key Laboratory of ASIC and System,Fudan University(Grant No.2019KF007)the Fund from the Suzhou Science and Technology Bureau(Grant No.SYG201933)the Fund from the Jiangsu Higher Education Institute of China(Grant No.19KJB510058).
文摘A new type of degradation phenomena featured with increased subthreshold swing and threshold voltage after negative gate bias stress(NBS)is observed for amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs),which can recover in a short time.After comparing with the degradation phenomena under negative bias illumination stress(NBIS),positive bias stress(PBS),and positive bias illumination stress(PBIS),degradation mechanisms under NBS is proposed to be the generation of singly charged oxygen vacancies(V_(o)^(+))in addition to the commonly reported doubly charged oxygen vacancies(V_(o)^(2+)).Furthermore,the NBS degradation phenomena can only be observed when the transfer curves after NBS are measured from the negative gate bias to the positive gate bias direction due to the fast recovery of V_(o)^(+)under positive gate bias.The proposed degradation mechanisms are verified by TCAD simulation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61971299 and 61974101)the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20201201)+1 种基金the Fund from Suzhou Science and Technology Bureau(Grant No.SYG201933)the Fund from the State Key Laboratory of ASIC and System,Fudan University(Grant No.2021KF005)
文摘The negative gate bias stress(NBS)reliability of n-type polycrystalline silicon(poly-Si)thin-film transistors(TFTs)with a distinct defective grain boundary(GB)in the channel is investigated.Results show that conventional NBS degradation with negative shift of the transfer curves is absent.The on-state current is decreased,but the subthreshold characteristics are not affected.The gate bias dependence of the drain leakage current at V_(ds)of 5.0 V is suppressed,whereas the drain leakage current at V_(ds)of 0.1 V exhibits obvious gate bias dependence.As confirmed via TCAD simulation,the corresponding mechanisms are proposed to be trap state generation in the GB region,positive-charge local formation in the gate oxide near the source and drain,and trap state introduction in the gate oxide.
基金Project supported in part by the National Natural Science Foundation of China(Grant Nos.61974101 and 61971299)the State Key Laboratory of ASIC and System,Fudan University(Grant No.2019KF007)+2 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.SBK2020021406)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.19KJB510058)the Suzhou Science and Technology Bureau(Grant No.SYG201933).
文摘Persistent photoconductivity(PPC)effect and its light-intensity dependence of both enhancement and depletion(E-/D-)mode amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs)are systematically investigated.Density of oxygen vacancy(V O)defects of E-mode TFTs is relatively small,in which formation of the photo-induced metastable defects is thermally activated,and the activation energy(E a)decreases continuously with increasing light-intensity.Density of V O defects of D-mode TFTs is much larger,in which the formation of photo-induced metastable defects is found to be spontaneous instead of thermally activated.Furthermore,for the first time it is found that a threshold dose of light-exposure is required to form fully developed photo-induced metastable defects.Under low light-exposure below the threshold,only a low PPC barrier is formed and the PPC recovery is fast.With increasing the light-exposure to the threshold,the lattice relaxation of metal cations adjacent to the doubly ionized oxygen vacancies(V O^2+)is fully developed,and the PPC barrier increases to∼0.25 eV,which remains basically unchanged under higher light-exposure.Based on the density of V O defects in the channel and the condition of light illumination,a unified model of formation of photo-induced metastable defects in a-IGZO TFTs is proposed to explain the experimental observations.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61971299 and 61974101)the Natural Science Foundation of Jiangsu Province of China(Grant No.BK20201201)+1 种基金the Fund from Suzhou Science and Technology Bureau(Grant No.SYG201933)the Fund from the State Key Laboratory of ASIC and System,Fudan University,(Grant No.2021KF005)。
文摘Degradation of a-InGaZnO thin-film transistors working under simultaneous DC gate and drain bias stress is investigated,and the corresponding degradation mechanism is proposed and verified.The maximum degradation occurs under the bias stress condition that makes the electric field and electron concentration relatively high at the same time.Trapping of hot electrons in the etching-stop layer under the extended drain electrode is proven to be the underlying mechanism.The observed degradation phenomena,including distortion in the transfer curve on a logarithmic scale and two-slope dependence on gate bias on a linear scale,current crowding in the output curve,and smaller degradation in transfer curves measured under large drain bias,can all be well explained with the proposed degradation mechanism.
基金supported by the National Natural Science Foundation of China (Grant No.60406001).
文摘The temperature distribution of typical n-type polycrystalline silicon thin film transistors under selfheating(SH)stress is studied by finite element analysis.From both steady-state and transient thermal simulation,the influence of device power density,substrate material,and channel width on device temperature distribution is analyzed.This study is helpful to understand the mechanism of SH degradation,and to effectively alleviate the SH effect in device operation.