Heavy ion irradiation effects on charge trapping memory(CTM)capacitors with TiN/Al_(2)O_(3)/HfO_(2)/Al_(2)O_(3)/HfO_(2)/SiO_(2)/p-Si structure have been investigated.The ion-induced interface charges and oxide trap ch...Heavy ion irradiation effects on charge trapping memory(CTM)capacitors with TiN/Al_(2)O_(3)/HfO_(2)/Al_(2)O_(3)/HfO_(2)/SiO_(2)/p-Si structure have been investigated.The ion-induced interface charges and oxide trap charges were calculated and analyzed by capacitance-voltage(C-V)characteristics.The C-V curves shift towards the negative direction after swift heavy ion irradiation,due to the net positive charges accumulating in the trapping layer.The memory window decreases with the increase of ion fluence at high voltage,which results from heavy ion-induced structural damage in the blocking layer.The mechanism of heavy ion irradiation effects on CTM capacitors is discussed in detail with energy band diagrams.The results may help to better understand the physical mechanism of heavy ion-induced degradation of CTM capacitors.展开更多
Because of the discrete charge storage mechanism, charge trapping memory(CTM) technique is a good candidate for aerospace and military missions. The total ionization dose(TID) effects on CTM cells with Al2O3/HfO2/...Because of the discrete charge storage mechanism, charge trapping memory(CTM) technique is a good candidate for aerospace and military missions. The total ionization dose(TID) effects on CTM cells with Al2O3/HfO2/Al2O3(AHA) high-k gate stack structure under in-situ 10 keV x-rays are studied. The C-V characteristics at different radiation doses demonstrate that charge stored in the device continues to be leaked away during the irradiation,thereby inducing the shift of flat band voltage(V(fb)). The dc memory window shows insignificant changes, suggesting the existence of good P/E ability. Furthermore, the physical mechanisms of TID induced radiation damages in AHA-based CTM are analyzed.展开更多
Impact of band-engineering to the performance of charge trapping memory with HfO2/Ta2O5/HfO2 (HTH) as the charge trapping layer is investigated. Compared with devices with the same total HfO2 thickness, structures w...Impact of band-engineering to the performance of charge trapping memory with HfO2/Ta2O5/HfO2 (HTH) as the charge trapping layer is investigated. Compared with devices with the same total HfO2 thickness, structures with Ta2O5 closer to substrates show larger program/erase window, because the 2nd HfO2 (next to blocking oxide) serving as part of blocking oxide reduces the current tunneling out of/in the charge trapping layer during program and erase. Moreover, trapped charge centroid is modulated and contributed more to the fiat-band voltage shift. Further experiments prove that devices with a thicker 2nd HfO2 layer exhibit larger saturate fiat-band shift in both program and erase operation. The optimized device achieves a 7 V memory window and good reliability characteristics.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
We have evaluated the effects of recombination processes in a charge storage layer, either between trapped electrons and trapped holes or between trapped carriers and free carriers, on charge trapping memory cell's p...We have evaluated the effects of recombination processes in a charge storage layer, either between trapped electrons and trapped holes or between trapped carriers and free carriers, on charge trapping memory cell's performances by numerical simulation. Recombination is an indispensable mechanism in charge trapping memory. It helps charge convert process between negative and positive charges in the charge storage layer during charge trapping memory programming/erasing operation. It can affect the speed of programming and erasing operations.展开更多
We evaluate the influence of the thermally assisted tunneling (TAT) mechanism on charge trapping memory (CTM) cell performance by numerical simulation, and comprehensively analyse the effects of the temperature, t...We evaluate the influence of the thermally assisted tunneling (TAT) mechanism on charge trapping memory (CTM) cell performance by numerical simulation, and comprehensively analyse the effects of the temperature, trap depth, distribution of trapped charge, gate voltage and parameters of TAT on erasing/programming speed and retention performance. TAT is an indispensable mechanism in CTM that can increase the detrapping probability of trapped charge. Our results reveal that the TAT effect causes the sensitivity of cell performance to temperature and it could affect the operational speed, especially for the erasing operation. The results show that the retention performance degrades compared with when the TAT mechanism is ignored.展开更多
In order to overcome the bit-to-bit interference of the traditional multi-level NAND type device, this paper firstly proposes a novel multi-bit non-uniform channel charge trapping memory (NUC-CTM) device with virtua...In order to overcome the bit-to-bit interference of the traditional multi-level NAND type device, this paper firstly proposes a novel multi-bit non-uniform channel charge trapping memory (NUC-CTM) device with virtual-source NAND-type array architecture, which can effectively restrain the second-bit effect (SBE) and provide 3-bit per cell capability. Owing to the n- buffer region, the SBE induced threshold voltage window shift can be reduced to less than 400 mV and the minimum threshold voltage window between neighboring levels is larger than 750 mV for reliable 3-bit operation. A silicon-rich SiON is also investigated as a trapping layer to improve the retention reliability of the NUC-CTM.展开更多
The accumulation process of trapped charges in a TANOS cell during P/E cycling is investigated via numerical simulation. The recombination process between trapped charges is an important issue on the retention of char...The accumulation process of trapped charges in a TANOS cell during P/E cycling is investigated via numerical simulation. The recombination process between trapped charges is an important issue on the retention of charge trapping memory. Our results show that accumulated trapped holes during P/E cycling can have an influence on retention, and the recombination mechanism between trapped charges should be taken into account when evaluating the retention capability of TANOS.展开更多
We propose and investigate a novel metal/SiO_2/Si_3N_4/SiO_2/SiGe charge trapping flash memory structure(named as MONOS), utilizing Si Ge as the buried channel. The fabricated memory device demonstrates excellent pr...We propose and investigate a novel metal/SiO_2/Si_3N_4/SiO_2/SiGe charge trapping flash memory structure(named as MONOS), utilizing Si Ge as the buried channel. The fabricated memory device demonstrates excellent programerasable characteristics attributed to the fact that more carriers are generated by the smaller bandgap of Si Ge during program/erase operations. A flat-band voltage shift 2.8 V can be obtained by programming at +11 V for 100 us. Meanwhile, the memory device exhibits a large memory window of ~7.17 V under ±12 V sweeping voltage, and a negligible charge loss of 18% after 104 s' retention. In addition, the leakage current density is lower than 2.52 × 10^(-7) A·cm^(-2) below a gate breakdown voltage of 12.5 V. Investigation of leakage current-voltage indicates that the Schottky emission is the predominant conduction mechanisms for leakage current. These desirable characteristics are ascribed to the higher trap density of the Si_3N_4 charge trapping layer and the better quality of the interface between the SiO_2 tunneling layer and the Si Ge buried channel. Therefore, the application of the Si Ge buried channel is very promising to construct 3 D charge trapping NAND flash devices with improved operation characteristics.展开更多
In this paper the endurance characteristics and trap generation are investigated to study the effects of different postdeposition anneals (PDAs) on the integrity of an Al2O3/Si3N4/SiOz/Si memory gate stack. The flat...In this paper the endurance characteristics and trap generation are investigated to study the effects of different postdeposition anneals (PDAs) on the integrity of an Al2O3/Si3N4/SiOz/Si memory gate stack. The flat-band voltage (Vfb) turnarounds are observed in both the programmed and erased states of the N2-PDA device. In contrast, this turnaround is observed only in the erased state of the O2-PDA device. The Vfb in the programmed state of the O2-PDA device keeps increasing with increasing program/erase (P/E) cycles. Through the analyses of endurance characteristics and the low voltage round-trip current transients, it is concluded that in both kinds of device there are an unknown type of pre-existing characteristic deep traps and P/E stress-induced positive oxide charges. In the O2-PDA device two extra types of trap are also found: the pre-existing border traps and the P/E stress-induced negative traps. Based on these four types of defects we can explain the endurance characteristics of two kinds of device. The switching property of pre-existing characteristic deep traps is also discussed.展开更多
Based on first principle calculations, a comprehensive study of substitutional oxygen defects in hexagonal silicon nitride (β-Si3N4) has been carried out. Firstly, it is found that substitutional oxygen is most lik...Based on first principle calculations, a comprehensive study of substitutional oxygen defects in hexagonal silicon nitride (β-Si3N4) has been carried out. Firstly, it is found that substitutional oxygen is most likely to form clusters at three sites in Si3N4 due to the intense attractive interaction between oxygen defects. Then, by using three analytical tools (trap energy, modified Bader analysis and charge density difference), we discuss the trap abilities of the three clusters. The result shows that each kind of cluster at the three specific sites presents very different abilities to trap charge carriers (electrons or holes): two of the three clusters can trap both kinds of charge carriers, confirming their amphoteric property; While the last remaining one is only able to trap hole carriers. Moreover, our studies reveal that the three clusters differ from each other in terms of endurance during the program/erase progress. Taking full account of capturing properties for the three oxygen clusters, including trap ability and endurance, we deem holes rather than electrons to be optimal to act as operational charge carriers for the oxygen defects in Si3N4-based charge trapping memories.展开更多
基金the National Natural Science Foundation of China(Grant Nos.12105340,12035019,and12075290)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2020412)。
文摘Heavy ion irradiation effects on charge trapping memory(CTM)capacitors with TiN/Al_(2)O_(3)/HfO_(2)/Al_(2)O_(3)/HfO_(2)/SiO_(2)/p-Si structure have been investigated.The ion-induced interface charges and oxide trap charges were calculated and analyzed by capacitance-voltage(C-V)characteristics.The C-V curves shift towards the negative direction after swift heavy ion irradiation,due to the net positive charges accumulating in the trapping layer.The memory window decreases with the increase of ion fluence at high voltage,which results from heavy ion-induced structural damage in the blocking layer.The mechanism of heavy ion irradiation effects on CTM capacitors is discussed in detail with energy band diagrams.The results may help to better understand the physical mechanism of heavy ion-induced degradation of CTM capacitors.
基金Supported by the National Natural Science Foundation of China under Grant No 616340084the Youth Innovation Promotion Association of Chinese Academy of Sciences under Grant No 2014101+1 种基金the International Cooperation Project of Chinese Academy of Sciencesthe Austrian-Chinese Cooperative R&D Projects under Grant No 172511KYSB20150006
文摘Because of the discrete charge storage mechanism, charge trapping memory(CTM) technique is a good candidate for aerospace and military missions. The total ionization dose(TID) effects on CTM cells with Al2O3/HfO2/Al2O3(AHA) high-k gate stack structure under in-situ 10 keV x-rays are studied. The C-V characteristics at different radiation doses demonstrate that charge stored in the device continues to be leaked away during the irradiation,thereby inducing the shift of flat band voltage(V(fb)). The dc memory window shows insignificant changes, suggesting the existence of good P/E ability. Furthermore, the physical mechanisms of TID induced radiation damages in AHA-based CTM are analyzed.
基金Supported by the National Basic Research Program of China under Grant No 2011CBA00602the National Key Scientific and Technological Project under Grant No 2013ZX01032001-001-003
文摘Impact of band-engineering to the performance of charge trapping memory with HfO2/Ta2O5/HfO2 (HTH) as the charge trapping layer is investigated. Compared with devices with the same total HfO2 thickness, structures with Ta2O5 closer to substrates show larger program/erase window, because the 2nd HfO2 (next to blocking oxide) serving as part of blocking oxide reduces the current tunneling out of/in the charge trapping layer during program and erase. Moreover, trapped charge centroid is modulated and contributed more to the fiat-band voltage shift. Further experiments prove that devices with a thicker 2nd HfO2 layer exhibit larger saturate fiat-band shift in both program and erase operation. The optimized device achieves a 7 V memory window and good reliability characteristics.
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.
基金supported by Samsung Electronics Co.Ltd and RFDP 20060001050
文摘We have evaluated the effects of recombination processes in a charge storage layer, either between trapped electrons and trapped holes or between trapped carriers and free carriers, on charge trapping memory cell's performances by numerical simulation. Recombination is an indispensable mechanism in charge trapping memory. It helps charge convert process between negative and positive charges in the charge storage layer during charge trapping memory programming/erasing operation. It can affect the speed of programming and erasing operations.
基金Project supported by the National Basic Research Program of China (Grant No. 2010CB934203)
文摘We evaluate the influence of the thermally assisted tunneling (TAT) mechanism on charge trapping memory (CTM) cell performance by numerical simulation, and comprehensively analyse the effects of the temperature, trap depth, distribution of trapped charge, gate voltage and parameters of TAT on erasing/programming speed and retention performance. TAT is an indispensable mechanism in CTM that can increase the detrapping probability of trapped charge. Our results reveal that the TAT effect causes the sensitivity of cell performance to temperature and it could affect the operational speed, especially for the erasing operation. The results show that the retention performance degrades compared with when the TAT mechanism is ignored.
基金Project supported by the National Basic Research Program of China(No.2006CB302700)
文摘In order to overcome the bit-to-bit interference of the traditional multi-level NAND type device, this paper firstly proposes a novel multi-bit non-uniform channel charge trapping memory (NUC-CTM) device with virtual-source NAND-type array architecture, which can effectively restrain the second-bit effect (SBE) and provide 3-bit per cell capability. Owing to the n- buffer region, the SBE induced threshold voltage window shift can be reduced to less than 400 mV and the minimum threshold voltage window between neighboring levels is larger than 750 mV for reliable 3-bit operation. A silicon-rich SiON is also investigated as a trapping layer to improve the retention reliability of the NUC-CTM.
基金Project supported by Samsung Electronics Co.Ltd.(Nos.20060001050,2006CB302705)
文摘The accumulation process of trapped charges in a TANOS cell during P/E cycling is investigated via numerical simulation. The recombination process between trapped charges is an important issue on the retention of charge trapping memory. Our results show that accumulated trapped holes during P/E cycling can have an influence on retention, and the recombination mechanism between trapped charges should be taken into account when evaluating the retention capability of TANOS.
基金Supported by the National Science and Technology Major Project of China under Grant No 2013ZX02303007the National Key Research and Development Program of China under Grant No 2016YFA0301701the Youth Innovation Promotion Association of the Chinese Academy of Sciences under Grant No 2016112
文摘We propose and investigate a novel metal/SiO_2/Si_3N_4/SiO_2/SiGe charge trapping flash memory structure(named as MONOS), utilizing Si Ge as the buried channel. The fabricated memory device demonstrates excellent programerasable characteristics attributed to the fact that more carriers are generated by the smaller bandgap of Si Ge during program/erase operations. A flat-band voltage shift 2.8 V can be obtained by programming at +11 V for 100 us. Meanwhile, the memory device exhibits a large memory window of ~7.17 V under ±12 V sweeping voltage, and a negligible charge loss of 18% after 104 s' retention. In addition, the leakage current density is lower than 2.52 × 10^(-7) A·cm^(-2) below a gate breakdown voltage of 12.5 V. Investigation of leakage current-voltage indicates that the Schottky emission is the predominant conduction mechanisms for leakage current. These desirable characteristics are ascribed to the higher trap density of the Si_3N_4 charge trapping layer and the better quality of the interface between the SiO_2 tunneling layer and the Si Ge buried channel. Therefore, the application of the Si Ge buried channel is very promising to construct 3 D charge trapping NAND flash devices with improved operation characteristics.
基金Project supported in part by the National Basic Research Program of China(Grant Nos.2010CB934200 and 2011CBA00600)the National Natural Science Foundation of China(Grant Nos.61176073 and 61176080)the Director’s Fund of the Institute of Microelectronics,Chinese Academy of Sciences
文摘In this paper the endurance characteristics and trap generation are investigated to study the effects of different postdeposition anneals (PDAs) on the integrity of an Al2O3/Si3N4/SiOz/Si memory gate stack. The flat-band voltage (Vfb) turnarounds are observed in both the programmed and erased states of the N2-PDA device. In contrast, this turnaround is observed only in the erased state of the O2-PDA device. The Vfb in the programmed state of the O2-PDA device keeps increasing with increasing program/erase (P/E) cycles. Through the analyses of endurance characteristics and the low voltage round-trip current transients, it is concluded that in both kinds of device there are an unknown type of pre-existing characteristic deep traps and P/E stress-induced positive oxide charges. In the O2-PDA device two extra types of trap are also found: the pre-existing border traps and the P/E stress-induced negative traps. Based on these four types of defects we can explain the endurance characteristics of two kinds of device. The switching property of pre-existing characteristic deep traps is also discussed.
基金supported by the National Youth Science Foundation of China(No.61006064)
文摘Based on first principle calculations, a comprehensive study of substitutional oxygen defects in hexagonal silicon nitride (β-Si3N4) has been carried out. Firstly, it is found that substitutional oxygen is most likely to form clusters at three sites in Si3N4 due to the intense attractive interaction between oxygen defects. Then, by using three analytical tools (trap energy, modified Bader analysis and charge density difference), we discuss the trap abilities of the three clusters. The result shows that each kind of cluster at the three specific sites presents very different abilities to trap charge carriers (electrons or holes): two of the three clusters can trap both kinds of charge carriers, confirming their amphoteric property; While the last remaining one is only able to trap hole carriers. Moreover, our studies reveal that the three clusters differ from each other in terms of endurance during the program/erase progress. Taking full account of capturing properties for the three oxygen clusters, including trap ability and endurance, we deem holes rather than electrons to be optimal to act as operational charge carriers for the oxygen defects in Si3N4-based charge trapping memories.