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
The effect of nitric oxide(NO) annealing on charge traps in the oxide insulator and transition layer in n-type4H–Si C metal–oxide–semiconductor(MOS) devices has been investigated using the time-dependent bias s...The effect of nitric oxide(NO) annealing on charge traps in the oxide insulator and transition layer in n-type4H–Si C metal–oxide–semiconductor(MOS) devices has been investigated using the time-dependent bias stress(TDBS),capacitance–voltage(C–V),and secondary ion mass spectroscopy(SIMS).It is revealed that two main categories of charge traps,near interface oxide traps(Nniot) and oxide traps(Not),have different responses to the TDBS and C–V characteristics in NO-annealed and Ar-annealed samples.The Nniotare mainly responsible for the hysteresis occurring in the bidirectional C–V characteristics,which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor.However,Not is mainly responsible for the TDBS induced C–V shifts.Electrons tunneling into the Not are hardly released quickly when suffering TDBS,resulting in the problem of the threshold voltage stability.Compared with the Ar-annealed sample,Nniotcan be significantly suppressed by the NO annealing,but there is little improvement of Not.SIMS results demonstrate that the Nniotare distributed within the transition layer,which correlated with the existence of the excess silicon.During the NO annealing process,the excess Si atoms incorporate into nitrogen in the transition layer,allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot.展开更多
The effect of substrate bias on the degradation during applying a negative bias temperature (NBT) stress is studied in this paper. With a smaller gate voltage stress applied, the degradation of negative bias tempera...The effect of substrate bias on the degradation during applying a negative bias temperature (NBT) stress is studied in this paper. With a smaller gate voltage stress applied, the degradation of negative bias temperature instability (NBTI) is enhanced, and there comes forth an inflexion point. The degradation pace turns larger when the substrate bias is higher than the inflexion point. The substrate hot holes can be injected into oxide and generate additional oxide traps, inducing an inflexion phenomenon. When a constant substrate bias stress is applied, as the gate voltage stress increases, an inflexion comes into being also. The higher gate voltage causes the electrons to tunnel into the substrate from the poly, thereby generating the electro,hole pairs by impact ionization. The holes generated by impact ionization and the holes from the substrate all can be accelerated to high energies by the substrate bias. More additional oxide traps can be produced, and correspondingly, the degradation is strengthened by the substrate bias. The results of the alternate stress experiment show that the interface traps generated by the hot holes cannot be annealed, which is different from those generated by common holes.展开更多
Different switching frequencies are required when SiC metal-oxide-semiconductor field-effect transistors(MOSFETs)are switching in a space environment.In this study,the total ionizing dose(TID)responses of SiC power MO...Different switching frequencies are required when SiC metal-oxide-semiconductor field-effect transistors(MOSFETs)are switching in a space environment.In this study,the total ionizing dose(TID)responses of SiC power MOSFETs are investigated under different switching frequencies from 1 kHz to 10 MHz.A significant shift was observed in the threshold voltage as the frequency increased,which resulted in premature failure of the drain-source breakdown voltage and drain-source leakage current.The degradation is attributed to the high activation and low recovery rates of traps at high frequencies.The results of this study suggest that a targeted TID irradiation test evaluation method can be developed according to the actual switching frequency of SiC power MOSFETs.展开更多
Deep submicron n-channel metal-oxide-semiconductor field-effect transistors (NMOSFETs) with shallow trench isolation (STI) are exposed to ionizing dose radiation under different bias conditions. The total ionizing...Deep submicron n-channel metal-oxide-semiconductor field-effect transistors (NMOSFETs) with shallow trench isolation (STI) are exposed to ionizing dose radiation under different bias conditions. The total ionizing dose radiation induced subthreshold leakage current increase and the hump effect under four different irradiation bias conditions including the worst case (ON bias) for the transistors are discussed. The high electric fields at the corners are partly responsible for the subthreshold hump effect. Charge trapped in the isolation oxide, particularly at the Si/SiO2 interface along the sidewalls of the trench oxide creates a leakage path, which becomes a dominant contributor to the offstate drain-to-source leakage current in the NMOSFET. Non-uniform charge distribution is introduced into a threedimensional (3D) simulation. Good agreement between experimental and simulation results is demonstrated. We find that the electric field distribution along with the STI sidewall is important for the radiation effect under different bias conditions.展开更多
Input/output devices for flash memory are exposed to gamma ray irradiation. Total ionizing dose has been shown great influence on characteristic degradation of transistors with different sizes. In this paper, we obser...Input/output devices for flash memory are exposed to gamma ray irradiation. Total ionizing dose has been shown great influence on characteristic degradation of transistors with different sizes. In this paper, we observed a larger increase of off-state leakage in the short channel device than in long one. However, a larger threshold voltage shift is observed for the narrow width device than for the wide one, which is well known as the radiation induced narrow channel effect. The radiation induced charge in the shallow trench isolation oxide influences the electric field of the narrow channel device. Also, the drain bias dependence of the off-state leakage after irradiation is observed, which is called the radiation enhanced drain induced barrier lowing effect. Finally, we found that substrate bias voltage can suppress the off-state leakage, while leading to more obvious hump effect.展开更多
In this paper, total ionizing dose effect of NMOS transistors in advanced CMOS technology are exam- ined. The radiation tests are performed at 60Co sources at the dose rate of 50 rad (Si)/s. The investigation's res...In this paper, total ionizing dose effect of NMOS transistors in advanced CMOS technology are exam- ined. The radiation tests are performed at 60Co sources at the dose rate of 50 rad (Si)/s. The investigation's results show that the radiation-induced charge buildup in the gate oxide can be ignored, and the field oxide isolation struc- ture is the main total dose problem. The total ionizing dose (TID) radiation effects of field oxide parasitic transistors are studied in detail. An analytical model of radiation defect charge induced by TID damage in field oxide is estab- lished. The I-V characteristics of the NMOS parasitic transistors at different doses are modeled by using a surface potential method. The modeling method is verified by the experimental I V characteristics of 180 nm commer- cial NMOS device induced by TID radiation at different doses. The model results are in good agreement with the radiation experimental results, which shows the analytical model can accurately predict the radiation response characteristics of advanced bulk CMOS technology device.展开更多
The effects of gamma irradiation on the shallow trench isolation(STI)leakage currents in a 0.18μm technology are investigated.NMOSFETs with different gate lengths are irradiated at several dose levels.The threshold...The effects of gamma irradiation on the shallow trench isolation(STI)leakage currents in a 0.18μm technology are investigated.NMOSFETs with different gate lengths are irradiated at several dose levels.The threshold voltage shift is negligible in all of the devices due to the very thin oxide thickness.However,an increase in the off-state leakage current is observed for all of the devices.We believe that the leakage is induced by the drain-to-source leakage path along the STI sidewall,which is formed by the positive trapped charge in the STI oxide.Also, we found that the leakage is dependent on the device's gate length.The three-transistor model(one main transistor with two parasitic transistors)can provide us with a brief understanding of the dependence on gate length.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 Nos.61404098 and 61274079)the Doctoral Fund of Ministry of Education of China(Grant No.20130203120017)+2 种基金the National Key Basic Research Program of China(Grant No.2015CB759600)the National Grid Science&Technology Project,China(Grant No.SGRI-WD-71-14-018)the Key Specific Project in the National Science&Technology Program,China(Grant Nos.2013ZX02305002-002 and 2015CB759600)
文摘The effect of nitric oxide(NO) annealing on charge traps in the oxide insulator and transition layer in n-type4H–Si C metal–oxide–semiconductor(MOS) devices has been investigated using the time-dependent bias stress(TDBS),capacitance–voltage(C–V),and secondary ion mass spectroscopy(SIMS).It is revealed that two main categories of charge traps,near interface oxide traps(Nniot) and oxide traps(Not),have different responses to the TDBS and C–V characteristics in NO-annealed and Ar-annealed samples.The Nniotare mainly responsible for the hysteresis occurring in the bidirectional C–V characteristics,which are very close to the semiconductor interface and can readily exchange charges with the inner semiconductor.However,Not is mainly responsible for the TDBS induced C–V shifts.Electrons tunneling into the Not are hardly released quickly when suffering TDBS,resulting in the problem of the threshold voltage stability.Compared with the Ar-annealed sample,Nniotcan be significantly suppressed by the NO annealing,but there is little improvement of Not.SIMS results demonstrate that the Nniotare distributed within the transition layer,which correlated with the existence of the excess silicon.During the NO annealing process,the excess Si atoms incorporate into nitrogen in the transition layer,allowing better relaxation of the interface strain and effectively reducing the width of the transition layer and the density of Nniot.
基金Project supported by the National Natural Science Foundation of China (Grant Nos 60376024,60736033 and 60506020)the National High Technology Research and Development Program of China (Grant No 2003AA1Z1630)
文摘The effect of substrate bias on the degradation during applying a negative bias temperature (NBT) stress is studied in this paper. With a smaller gate voltage stress applied, the degradation of negative bias temperature instability (NBTI) is enhanced, and there comes forth an inflexion point. The degradation pace turns larger when the substrate bias is higher than the inflexion point. The substrate hot holes can be injected into oxide and generate additional oxide traps, inducing an inflexion phenomenon. When a constant substrate bias stress is applied, as the gate voltage stress increases, an inflexion comes into being also. The higher gate voltage causes the electrons to tunnel into the substrate from the poly, thereby generating the electro,hole pairs by impact ionization. The holes generated by impact ionization and the holes from the substrate all can be accelerated to high energies by the substrate bias. More additional oxide traps can be produced, and correspondingly, the degradation is strengthened by the substrate bias. The results of the alternate stress experiment show that the interface traps generated by the hot holes cannot be annealed, which is different from those generated by common holes.
基金supported by the National Natural Science Foundation of China under Grant No.11975305the West Light Foundation of The Chinese Academy of Sciences,Grant No.2017-XBQNXZ-B-008。
文摘Different switching frequencies are required when SiC metal-oxide-semiconductor field-effect transistors(MOSFETs)are switching in a space environment.In this study,the total ionizing dose(TID)responses of SiC power MOSFETs are investigated under different switching frequencies from 1 kHz to 10 MHz.A significant shift was observed in the threshold voltage as the frequency increased,which resulted in premature failure of the drain-source breakdown voltage and drain-source leakage current.The degradation is attributed to the high activation and low recovery rates of traps at high frequencies.The results of this study suggest that a targeted TID irradiation test evaluation method can be developed according to the actual switching frequency of SiC power MOSFETs.
文摘Deep submicron n-channel metal-oxide-semiconductor field-effect transistors (NMOSFETs) with shallow trench isolation (STI) are exposed to ionizing dose radiation under different bias conditions. The total ionizing dose radiation induced subthreshold leakage current increase and the hump effect under four different irradiation bias conditions including the worst case (ON bias) for the transistors are discussed. The high electric fields at the corners are partly responsible for the subthreshold hump effect. Charge trapped in the isolation oxide, particularly at the Si/SiO2 interface along the sidewalls of the trench oxide creates a leakage path, which becomes a dominant contributor to the offstate drain-to-source leakage current in the NMOSFET. Non-uniform charge distribution is introduced into a threedimensional (3D) simulation. Good agreement between experimental and simulation results is demonstrated. We find that the electric field distribution along with the STI sidewall is important for the radiation effect under different bias conditions.
文摘Input/output devices for flash memory are exposed to gamma ray irradiation. Total ionizing dose has been shown great influence on characteristic degradation of transistors with different sizes. In this paper, we observed a larger increase of off-state leakage in the short channel device than in long one. However, a larger threshold voltage shift is observed for the narrow width device than for the wide one, which is well known as the radiation induced narrow channel effect. The radiation induced charge in the shallow trench isolation oxide influences the electric field of the narrow channel device. Also, the drain bias dependence of the off-state leakage after irradiation is observed, which is called the radiation enhanced drain induced barrier lowing effect. Finally, we found that substrate bias voltage can suppress the off-state leakage, while leading to more obvious hump effect.
基金Project supported by the National Natural Science Foundation of China(No.11305126)
文摘In this paper, total ionizing dose effect of NMOS transistors in advanced CMOS technology are exam- ined. The radiation tests are performed at 60Co sources at the dose rate of 50 rad (Si)/s. The investigation's results show that the radiation-induced charge buildup in the gate oxide can be ignored, and the field oxide isolation struc- ture is the main total dose problem. The total ionizing dose (TID) radiation effects of field oxide parasitic transistors are studied in detail. An analytical model of radiation defect charge induced by TID damage in field oxide is estab- lished. The I-V characteristics of the NMOS parasitic transistors at different doses are modeled by using a surface potential method. The modeling method is verified by the experimental I V characteristics of 180 nm commer- cial NMOS device induced by TID radiation at different doses. The model results are in good agreement with the radiation experimental results, which shows the analytical model can accurately predict the radiation response characteristics of advanced bulk CMOS technology device.
文摘The effects of gamma irradiation on the shallow trench isolation(STI)leakage currents in a 0.18μm technology are investigated.NMOSFETs with different gate lengths are irradiated at several dose levels.The threshold voltage shift is negligible in all of the devices due to the very thin oxide thickness.However,an increase in the off-state leakage current is observed for all of the devices.We believe that the leakage is induced by the drain-to-source leakage path along the STI sidewall,which is formed by the positive trapped charge in the STI oxide.Also, we found that the leakage is dependent on the device's gate length.The three-transistor model(one main transistor with two parasitic transistors)can provide us with a brief understanding of the dependence on gate length.