共查询到18条相似文献,搜索用时 140 毫秒
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介绍了在纳米晶浮栅存储器数据保持特性方面的研究工作,重点介绍了纳米晶材料的选择与制备和遂穿介质层工程。研究证明,金属纳米晶浮栅存储器比半导体纳米晶浮栅存储器具有更好的电荷保持特性。并且金属纳米晶制备方法简单,通过电子束蒸发热退火的方法就能够得到质量较好的金属纳米晶,密度约4×1011cm-2,纳米晶尺寸约6~7nm。实验证明,高介电常数隧穿介质能够明显改善浮栅存储器的电荷保持特性,所以在引入金属纳米晶和高介电常数遂穿介质之后,纳米晶浮栅存储器可能成为下一代非挥发性存储器的候选者。 相似文献
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快速退火纳米晶化法是目前常用的金属纳米晶制备方法,但其后续600~900℃高温退火会降低器件的电学特性和可靠性。本文提出了热预算低的金属纳米晶制备的新方法—沉积过程中的同步金属薄膜原位纳米晶化法,可以省掉后续单独的退火处理工艺,使金属薄膜同步产生纳米晶化,降低工艺热功耗及简化工艺,从而有效地改善上述薄膜沉积后退火纳米晶化法的不足。在不同衬底温度(250~325 ?C)下,利用同步纳米晶化法制备镍纳米晶存储器。随着生长温度的增加,其存储窗口先增加到最大值再降低。衬底温度为300 ?C时,其存储窗口(2.78 V)最大。与快速热退火法镍纳米晶存储器相比较,同步纳米晶化法制备镍纳米晶存储器具有更强的电荷存储能力。另外,研究了不同操作电压和脉冲时间下器件的平带电压偏移量,当操作电压增加到±10 V时出现了较大的平带电压偏移量,这表明器件发生了大量的载流子(电子和空穴)注入现象。最后,模拟了金属纳米晶存储器的载流子(电子和空穴)注入和释放过程。 相似文献
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硅纳米晶非挥发存储器由于其卓越的性能以及与传统工艺的高度兼容性,近来引起高度关注。采用两步低压化学气相淀积(LPCVD)生长方式制备硅纳米晶(Si-NC),该方法所制备的硅纳米晶具有密度高、可控性好的特点,且完全兼容于传统CMOS工艺。在此基础上制作四端硅纳米晶非挥发存储器,该器件展示出良好的存储特性,包括10 V操作电压下快速地擦写,数据保持特性的显著提高,以及在105次擦写周期以后阈值电压(Vt)飘移低于10%的良好耐受性。该器件在未来高性能非挥发存储器应用上极具潜质。 相似文献
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3C行业的不断发展,催生了对高密度、持久保存、快速擦写、鲁棒可靠性的非易失性存储器(如flash)的持续需求,促使我们在科研上不断地深入研究新材料、新工艺。在本文中,我们首次采用了区别于传统CMOS工艺的两步工艺方法来制作金属纳米晶非易失性存储器。这种方法,由于将金纳米晶的化学合成和后续组装分离开来,所以能够独立地调节纳米晶的尺寸和组装密度,而且可以很好地避免一直困扰的金属扩散问题。最终的形貌表征和电学测量结果,证实存在一个最优化的纳米晶密度--在这个最优化条件下,我们的存储器件,既有持久的保存时间,又有较大的存储窗口。而组装密度的可调,同时可以满足我们对于大的存储窗口/较长保存时间某一方面的偏好。这些实验结果,都很好地证明了我们两步工艺方法的可行性。 相似文献
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Chungho Lee Ganguly U. Narayanan V. Tuo-Hung Hou Jinsook Kim Kan E.C. 《Electron Device Letters, IEEE》2005,26(12):879-881
The electrostatic model for nanocrystal memories is used to illustrate the fundamental difference of the metal nanocrystal memory in low-voltage program/erase (P/E) operations in comparison with semiconductor nanocrystal and trap-based memories. Due to repulsion of potential contours inside conductors, the metal nanocrystals will significantly enhance the electric field between the nanocrystal and the sensing channel set up by the control gate bias and, hence, can achieve much higher efficiency in low-voltage P/E. On the other hand, the electric field originated from the stored charge will only be slightly different for metal and semiconductor nanocrystal cases. We presented the electrostatic models by both approximate analytical formulation and three-dimensional numerical simulation in a nanocrystal array. Operations of P/E and read disturbance were analyzed for the cases of homogeneous charge distribution, silicon, and metal nanocrystals. In the P/E condition of +5/-5 V, the metal nanocrystal memory offers around 1.6 times higher peak fields than Si counterparts and almost three times higher than that from the one-dimensional model for homogeneous charge distribution. The field enhancement factor suggests the design criteria of oxide thickness, nanocrystal size, and spacing. The advantage of asymmetric field enhancement of metal nanocrystals will be even more prominent when high-K gate dielectrics are employed. 相似文献
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Self-assembly of metal nanocrystals on ultrathin oxide for nonvolatile memory applications 总被引:3,自引:0,他引:3
Chungho Lee Jami Meteer Venkat Narayanan Edwin C. Kan 《Journal of Electronic Materials》2005,34(1):1-11
The self-assembly of metal nanocrystals including Au, Ag, and Pt on ultrathin oxide for nonvolatile memory applications are
investigated. The self-assembly of nanocrystals consists of metal evaporation and selective rapid-thermal annealing (RTA).
By controlling process parameters, such as the thickness of the deposited film, the post-deposition annealing temperatures,
and the substrate doping concentration, metal nanocrystals with density of 2–4 × 1011 cm−2, diameter less than 8.1 nm, and diameter deviation less than 1.7 nm can be obtained. Observation by scanning-transmission
electron microscopy (STEM) and convergent-beam electron diffraction (CBED) shows that nanocrystals embedded in the oxide are
nearly spherical and crystalline. Metal contamination of the Si/SiO2 interface is negligible, as monitored by STEM, energy dispersive x-ray spectroscopy (EDX), and capacitance-voltage (C-V)
measurements. The electrical characteristics of metal, nanocrystal nonvolatile memories also show advantages over semiconductor
counterparts. Large memory windows shown by metal nanocrystal devices in C-V measurements demonstrate that the work functions
of metal nanocrystals are related to the charge-storage capacity and retention time because of the deeper potential well in
comparison with Si nanocrystals. 相似文献
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《Electron Devices, IEEE Transactions on》2009,56(8):1729-1735
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Heterogeneous floating-gates consisting of metal nanocrystals and silicon nitride (Si/sub 3/N/sub 4/) for nonvolatile memory applications have been fabricated and characterized. By combining the self-assembled Au nanocrystals and plasma-enhanced chemical vapor deposition (PECVD) nitride layer, the heterogeneous-stack devices can achieve enhanced retention, endurance, and low-voltage program/erase characteristics over single-layer nanocrystals or nitride floating-gate memories. The metal nanocrystals at the lower stack enable the direct tunneling mechanism during program/erase to achieve low-voltage operation and good endurance, while the nitride layer at the upper stack works as an additional charge trap layer to enlarge the memory window and significantly improve the retention time. The write/erase time of the heterogeneous stack is almost the same as that of the single-layer metal nanocrystals. In addition, we could further enhance the memory window by stacking more nanocrystal/nitride heterogeneous layers, as long as the effective oxide thickness from the control gate is still within reasonable ranges to control the short channel effects. 相似文献
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P. Chakraborty S.S. Mahato M.K. Bera S.K. Samanta C.K. Maiti 《Microelectronic Engineering》2009,86(3):299-302
Potential of high-k dielectric films for future scaled charge storage non-volatile memory (NVM) device applications is discussed. To overcome the problems of charge loss encountered in conventional flash memories with silicon-nitride (Si3N4) films and polysilicon-oxide-nitride-oxide-silicon (SONOS) and nonuniformity issues in nanocrystal memories (NC), such as Si, Ge and metal, it is shown that the use of high-k dielectrics allows more aggressive scaling of the tunnel dielectric, smaller operating voltage, better endurance, and faster program/erase speeds. Charge-trapping characteristics of high-k AlN films with SiO2 as a blocking oxide in p-Si/SiO2/AlN/SiO2/poly-silicon (SOHOS) memory structures have been investigated in detail. The experimental results of program/erase characteristics obtained as the functions of gate bias voltage and pulse width are presented. 相似文献
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Fabrication of nickel nanocrystal flash memories using a polymeric approach is presented. Heat treatment of the poly (styrene-b-methyl methacrylate) block copolymer with a molecular weight of 67 000 g/mol followed by PMMA removal in an organic solvent created a porous PS film with 20-nm-diameter pores and a total pore density of ~6 times 1010 cm-2. A trilayer pattern-transfer approach was employed in order to solve the metal lift-off issue intertwined with the low aspect ratio block copolymer patterns. As a result, a highly uniform self- assembled array of nickel nanocrystals was attained and utilized for flash memory fabrication. The memory devices demonstrated an unchanged memory window for up to 2 times 105 stressing cycles. 相似文献
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Metal nanocrystal memories. I. Device design and fabrication 总被引:1,自引:0,他引:1
Liu Z. Lee C. Narayanan V. Pei G. Kan E.C. 《Electron Devices, IEEE Transactions on》2002,49(9):1606-1613
This paper describes the design principles and fabrication process of metal nanocrystal memories. The advantages of metal nanocrystals over their semiconductor counterparts include higher density of states, stronger coupling with the channel, better size scalability, and the design freedom of engineering the work functions to optimize device characteristics. One-dimensional (1-D) analyses are provided to illustrate the concept of work function engineering, both in direct-tunneling and F-N-tunneling regimes. A self-assembled nanocrystal formation process by rapid thermal annealing of ultrathin metal film deposited on top of gate oxide is developed and integrated with NMOSFET to fabricate such devices 相似文献