Si-rich silicon nitride films are prepared by plasma-enhanced chemical vapor deposition method, followed by thermal annealing to form the Si nanocrystals（Si-NCs） embedded in Si Nx floating gate MOS structures. The c...Si-rich silicon nitride films are prepared by plasma-enhanced chemical vapor deposition method, followed by thermal annealing to form the Si nanocrystals（Si-NCs） embedded in Si Nx floating gate MOS structures. The capacitance–voltage（C–V）, current–voltage（I–V）, and admittance–voltage（G–V） measurements are used to investigate the charging characteristics. It is found that the maximum flat band voltage shift（△VFB） due to full charged holes（～ 6.2 V） is much larger than that due to full charged electrons（～ 1 V）. The charging displacement current peaks of electrons and holes can be also observed by the I–V measurements, respectively. From the G–V measurements we find that the hole injection is influenced by the oxide hole traps which are located near the Si O2/Si-substrate interface. Combining the results of C–V and G–V measurements, we find that the hole charging of the Si-NCs occurs via a two-step tunneling mechanism. The evolution of G–V peak originated from oxide traps exhibits the process of hole injection into these defects and transferring to the Si-NCs.展开更多
A model based on analysis of the self-consistent Poisson-Schrodinger equation is proposed to investigate the tunneling current of electrons in the inversion layer of a p-type metal-oxide-semiconductor （MOS） structur...A model based on analysis of the self-consistent Poisson-Schrodinger equation is proposed to investigate the tunneling current of electrons in the inversion layer of a p-type metal-oxide-semiconductor （MOS） structure. In this model, the influences of interface trap charge （ITC） at the Si-SiO2 interface and fixed oxide charge （FOC） in the oxide region are taken into account, and one-band effective mass approximation is used. The tunneling probability is obtained by employing the transfer matrix method. Further, the effects of in-plane momentum on the quantization in the electron motion perpendicular to the Si-SiO2 interface of a MOS device are investigated. Theoretical simulation results indicate that both ITC and FOC have great influence on the tunneling current through a MOS structure when their densities are larger than l012 cm 2, which results from the great change of bound electrons near the Si-SiO2 interface and the oxide region. Therefore, for real ultrathin MOS structures with ITC and FOC, this model can give a more accurate description for the tunneling current in the inversion layer.展开更多
In this work, the trap-assisted tunneling（TAT） mechanism is modeled as a two-step physical process for charge trapping memory（CTM）. The influence of the TAT mechanism on CTM performance is investigated in consider...In this work, the trap-assisted tunneling（TAT） mechanism is modeled as a two-step physical process for charge trapping memory（CTM）. The influence of the TAT mechanism on CTM performance is investigated in consideration of various trap positions and energy levels. For the simulated CTM structure, simulation results indicate that the positions of oxide traps related to the maximum TAT current contribution shift towards the substrate interface and charge storage layer interface during time evolutions in programming and retention operations, respectively. Lower programming voltage and retention operations under higher temperature are found to be more sensitive to tunneling oxide degradation.展开更多
By measurement,we investigate the characteristics and location of gate oxide damage induced by snapback stress. The damage incurred during stress causes device degradation that follows an approximate power law with st...By measurement,we investigate the characteristics and location of gate oxide damage induced by snapback stress. The damage incurred during stress causes device degradation that follows an approximate power law with stress time. Oxide traps generated by stress will cause the increase of stress-induced leakage current and the decrease of Qbd （charge to breakdown）,and it may also cause the degradation of off-state drain leakage current. Stress-induced gate oxide damage is located not only in the drain side but also in the source side. The tertiary electrons generated by hot holes move toward Si-SiO2 interface under the electrical field toward the substrate,which explains the source side gate oxide damage.展开更多
The total-dose response and annealing effect of p-channel metal oxide semiconductor field-effect transistors （PMOSFETs） were investigated at various dose rates and biasing conditions.The results show that the shift ...The total-dose response and annealing effect of p-channel metal oxide semiconductor field-effect transistors （PMOSFETs） were investigated at various dose rates and biasing conditions.The results show that the shift of threshold voltage is more obvious when the dose rate is decreased.Under the various dose rates and biasing conditions,some have exhibited a time-dependent effect and others showed enhanced low-dose-rate sensitivity（ELDRS）.Finally,using the subthreshold-separating method,the threshold-voltage shift is separated into shifts due to interface states and oxidetrapped charges,and the underlying mechanisms of the observed effects are discussed.It has been indicated that the ELDRS effect results from the different quantities of the interface states generated at high and low dose rates.展开更多
The hot-carrier-induced on-resistance degradations of step gate oxide NLDMOS （SG-NLDMOS） transistors are investigated in detail by a DC voltage stress experiment, a TCAD simulation and a charge pumping test. For dif...The hot-carrier-induced on-resistance degradations of step gate oxide NLDMOS （SG-NLDMOS） transistors are investigated in detail by a DC voltage stress experiment, a TCAD simulation and a charge pumping test. For different stress conditions, degradation behaviors of SG-NLDMOS transistors are analyzed and degradation mechanisms are presented. Then the effect of various doses of n-type drain drift （NDD） region implant on Ron degradation is investigated. Experimental results show that a lower NDD dosage can reduce the hot-carrier induced Ron degradation effectively, which is different from uniform gate oxide NLDMOS （UG-NLDMOS） transistors.展开更多
We studied the oxygen etching of individual single-walled carbon nanotubes on silicon oxide substrates using atomic force microscopy and high-temperature environmental scanning electron microscopy. Our in situ observa...We studied the oxygen etching of individual single-walled carbon nanotubes on silicon oxide substrates using atomic force microscopy and high-temperature environmental scanning electron microscopy. Our in situ observations show that carbon nanotubes are not progressively etched from their ends, as frequently assumed, but disappear segment by segment. Atomic force microscopy, before and after oxidation, reveals that the oxidation of carbon nanotubes on substrates proceeds through a local cutting that is followed by a rapid etching of the disconnected nanotube segment. Unexpectedly, semiconducting nanotubes appear more reactive under these conditions than metallic ones. We also show that exposure to electron and laser beams locally increases the chemical reactivity of carbon nanotubes on such substrates. These results are rationalized by considering the effect of substrate-trapped charges on the nanotube density of states close to the Fermi level, which is impacted by the substrate type and the exposure to electron and laser beams.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2010CB934402)the National Natural Science Foundation of China(Grant No.11374153)
文摘Si-rich silicon nitride films are prepared by plasma-enhanced chemical vapor deposition method, followed by thermal annealing to form the Si nanocrystals（Si-NCs） embedded in Si Nx floating gate MOS structures. The capacitance–voltage（C–V）, current–voltage（I–V）, and admittance–voltage（G–V） measurements are used to investigate the charging characteristics. It is found that the maximum flat band voltage shift（△VFB） due to full charged holes（～ 6.2 V） is much larger than that due to full charged electrons（～ 1 V）. The charging displacement current peaks of electrons and holes can be also observed by the I–V measurements, respectively. From the G–V measurements we find that the hole injection is influenced by the oxide hole traps which are located near the Si O2/Si-substrate interface. Combining the results of C–V and G–V measurements, we find that the hole charging of the Si-NCs occurs via a two-step tunneling mechanism. The evolution of G–V peak originated from oxide traps exhibits the process of hole injection into these defects and transferring to the Si-NCs.
基金Project supported by the National Natural Science Foundation of China (Grant No. 61076055)the Program for Innovative Research Team of Zhejiang Normal University of China (Grant No. 2007XCXTD-5)the Open Program of Surface Physics Laboratory of Fudan University, China (Grant No. FDSKL2011-04)
文摘A model based on analysis of the self-consistent Poisson-Schrodinger equation is proposed to investigate the tunneling current of electrons in the inversion layer of a p-type metal-oxide-semiconductor （MOS） structure. In this model, the influences of interface trap charge （ITC） at the Si-SiO2 interface and fixed oxide charge （FOC） in the oxide region are taken into account, and one-band effective mass approximation is used. The tunneling probability is obtained by employing the transfer matrix method. Further, the effects of in-plane momentum on the quantization in the electron motion perpendicular to the Si-SiO2 interface of a MOS device are investigated. Theoretical simulation results indicate that both ITC and FOC have great influence on the tunneling current through a MOS structure when their densities are larger than l012 cm 2, which results from the great change of bound electrons near the Si-SiO2 interface and the oxide region. Therefore, for real ultrathin MOS structures with ITC and FOC, this model can give a more accurate description for the tunneling current in the inversion layer.
基金supported by the National Natural Science Foundation of China(Grant Nos.61404005,61421005,and 91434201)
文摘In this work, the trap-assisted tunneling（TAT） mechanism is modeled as a two-step physical process for charge trapping memory（CTM）. The influence of the TAT mechanism on CTM performance is investigated in consideration of various trap positions and energy levels. For the simulated CTM structure, simulation results indicate that the positions of oxide traps related to the maximum TAT current contribution shift towards the substrate interface and charge storage layer interface during time evolutions in programming and retention operations, respectively. Lower programming voltage and retention operations under higher temperature are found to be more sensitive to tunneling oxide degradation.
文摘By measurement,we investigate the characteristics and location of gate oxide damage induced by snapback stress. The damage incurred during stress causes device degradation that follows an approximate power law with stress time. Oxide traps generated by stress will cause the increase of stress-induced leakage current and the decrease of Qbd （charge to breakdown）,and it may also cause the degradation of off-state drain leakage current. Stress-induced gate oxide damage is located not only in the drain side but also in the source side. The tertiary electrons generated by hot holes move toward Si-SiO2 interface under the electrical field toward the substrate,which explains the source side gate oxide damage.
文摘The total-dose response and annealing effect of p-channel metal oxide semiconductor field-effect transistors （PMOSFETs） were investigated at various dose rates and biasing conditions.The results show that the shift of threshold voltage is more obvious when the dose rate is decreased.Under the various dose rates and biasing conditions,some have exhibited a time-dependent effect and others showed enhanced low-dose-rate sensitivity（ELDRS）.Finally,using the subthreshold-separating method,the threshold-voltage shift is separated into shifts due to interface states and oxidetrapped charges,and the underlying mechanisms of the observed effects are discussed.It has been indicated that the ELDRS effect results from the different quantities of the interface states generated at high and low dose rates.
基金Project supported by the National Science & Technology Major Project of China(No.2009ZX01033-001-003)
文摘The hot-carrier-induced on-resistance degradations of step gate oxide NLDMOS （SG-NLDMOS） transistors are investigated in detail by a DC voltage stress experiment, a TCAD simulation and a charge pumping test. For different stress conditions, degradation behaviors of SG-NLDMOS transistors are analyzed and degradation mechanisms are presented. Then the effect of various doses of n-type drain drift （NDD） region implant on Ron degradation is investigated. Experimental results show that a lower NDD dosage can reduce the hot-carrier induced Ron degradation effectively, which is different from uniform gate oxide NLDMOS （UG-NLDMOS） transistors.
文摘We studied the oxygen etching of individual single-walled carbon nanotubes on silicon oxide substrates using atomic force microscopy and high-temperature environmental scanning electron microscopy. Our in situ observations show that carbon nanotubes are not progressively etched from their ends, as frequently assumed, but disappear segment by segment. Atomic force microscopy, before and after oxidation, reveals that the oxidation of carbon nanotubes on substrates proceeds through a local cutting that is followed by a rapid etching of the disconnected nanotube segment. Unexpectedly, semiconducting nanotubes appear more reactive under these conditions than metallic ones. We also show that exposure to electron and laser beams locally increases the chemical reactivity of carbon nanotubes on such substrates. These results are rationalized by considering the effect of substrate-trapped charges on the nanotube density of states close to the Fermi level, which is impacted by the substrate type and the exposure to electron and laser beams.
