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基于密度泛函理论的第一性原理平面波超软赝势方法和VASP软件对电荷俘获存储器过擦现象进行了分析研究. 通过形成能的计算，确定了含有氮空位缺陷的Si3N4和含有间隙氧缺陷的HfO2作为研究的对象；俘获能的计算结果表明两种体系对电子的俘获能力比对空穴的大，因而对两体系擦写载流子确定为电子. 分别计算了HfO2和Si3N4 擦写前后的能量、擦写前后电荷分布变化、吸附能和态密度，以说明过擦的微观机理. 对能量和擦写电荷变化的研究，表明Si3N4相比于HfO2，其可靠性较差，且Si3N4 作为俘获层，在一个擦写周期后，晶胞中电子出现减少现象；界面吸附能的研究表明，Si3N4相比于HfO2在缺陷处更容易与氧进行电子交换；最后，通过对态密度的分析表明Si3N4和HfO2在对应的缺陷中均有缺陷能级俘获电子，前者为浅能级俘获，后者为深能级俘获. 综上分析表明，Si3N4在氮空位的作用下，缺陷附近原子对电子的局域作用变弱，使得Si3N4作为俘获层时，材料本身的电子被擦出，使得擦操作时的平带偏移电压增大，导致存储器发生过擦. 本文的研究结果揭示了过擦的本质，对提高电荷俘获存储器的可靠性以及存储特性有着重要的指导意义.In this paper, charge trapping memory (CTM) is studied for analyzing the over-erase phenomenon, based on the first principles and VASP package. The nitrogen vacancy (VN) in Si3N4 and the interstitial oxygen (IO) in HfO2 are selected as model, because of the formation energy. The result about trapping energy shows that the electrons are trapped more easily than holes in these models, so the electrons are selected as programming/erase object. The energy after programming/erase operation, Bader charge analysis, different charge densities, adsorption energy and density of states are all studied to explain the over-erase micro change. The energy and electron change show that HfO2 as trapping layer makes CTM more reliable than Si3N4 as trapping layer; and after a programming/erase cycle, electrons in Si3N4 are erased more than programming ones; and the result of adsorption energy shows that the electrons can exchange more easily in Si3N4 than in HfO2. Finally, the research on the density of states shows that Si3N4 has shallow trapping energy level, HfO2 has deep trapping energy level. In conclusion, the essence of the over-erase in Si3N4 is that the atoms near the defect have weaker localized action on the electrons, resulting in the instinct electrons that are erased in erase operation. The over-erase essence is revealed, which is of benefit to improving the reliability and retention.
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Keywords:
- over-erase /
- HfO2 /
- Si3N4 /
- the first principles
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[19] Wang W C, Xiong K, Wallace R M, Cho K 2010 J. Phys. Chem. C 114 22610
[20] Zhao Q, Zhou M X, Zhang W, Liu Q, Li XF, Liu M, Dai Y H 2013 J. Semicond. 34 032001
[21] Giacomazzi L, Umari P 2009 Phys. Rev. B 80 144201
[22] Wang J Y, Zhao Y Y, Xu J B, Dai Y H 2014 Acta Phys. Sin. 63 053101 (in Chinese) [汪家余, 赵远洋, 徐建彬, 代月花 2014 63 053101]
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[1] Jin L 2012 Ph. D. Dissertation (Hefei: Anhui University) (in Chinese) [金林 2012 博士学位论文 (合肥: 安徽大学)]
[2] Jin L, Zhang M H, Huo Z L, Yu Z A, Jiang D D, Wang Y, BAI Jie, Chen J N, Liu M 2012 Sci. China Tech. Sci. 55 888
[3] Sabina S, Francesco D, Alessio L, Gabriele C, Olivier S 2012 Appl. Phys. Exp. 5 021102
[4] Fu J, Singh N, Yang B, Zhu C X, Lo G Q, Kwong D L 2008 IEEE Elec. Dev. Lett. 29 518
[5] Zeng Y J, Dai Y H, Chen J N 2012 Mater. Struct. 49 382 (in Chinese) [曾叶娟, 代月花, 陈军宁 2012 材料与结构 49 382]
[6] Tan Y N, Chim W K, Cho B J, Choi W K 2004 IEEE Trans. Elec. Dev. 51 1143
[7] Cho M K, Kim D M 2000 IEEE Elec. Dev. Lett. 21 399
[8] Zhang Y Y, Shao T M, Su K 2013 Chin. Phys. B 22 053403
[9] Chevrier V L, Zwanziger J W, Dahn J R 2010 J. Alloys Compod. 496 25
[10] Henkelman G, Arnaldsson A, Jónsson H 2006 Computat. Mater. Sci. 36 354
[11] Wu T Q, Wang X Y, Jiao Z W, Luo H L, Zhu P 2013 Acta Phys. Sin. 62 186301 (in Chinese) [吴太权, 王新燕, 焦志伟, 罗宏雷, 朱萍 2013 62 186301]
[12] Hu M, Wang W D, Zeng P, Zeng J, Qin Y X 2012 Chin. Phys. B 21 023101
[13] Prada S, Rosa M, Giordano L, Valentin C D, Pacchioni G 2011 Phys. Rev. B 83 245314
[14] Pan Y, Guan W M, Chen S, Zhang K H 2011 Rare Metal Mater. Engineer. 40 80 (in Chinese) [潘勇, 管伟明, 陈松, 张昆华 2011 稀有金属材料与工程 40 80]
[15] Larcher L, Padovani A, Vandelli L, Pavan P 2011 Microelectr. Engineer. 88 1168
[16] Song Y C, Liu X Y, Du G, Kang J F, Han R Q 2008 Chin. Phys. B 17 2678
[17] Jarolimek K, de Groot R A, de Wijs G A, Zeman M 2010 Phys. Rev. B 82 205201
[18] Zhang Y Y, Shao T M, Su K 2013 Chin. Phys. B 22 053403
[19] Wang W C, Xiong K, Wallace R M, Cho K 2010 J. Phys. Chem. C 114 22610
[20] Zhao Q, Zhou M X, Zhang W, Liu Q, Li XF, Liu M, Dai Y H 2013 J. Semicond. 34 032001
[21] Giacomazzi L, Umari P 2009 Phys. Rev. B 80 144201
[22] Wang J Y, Zhao Y Y, Xu J B, Dai Y H 2014 Acta Phys. Sin. 63 053101 (in Chinese) [汪家余, 赵远洋, 徐建彬, 代月花 2014 63 053101]
[23] Luo J, Lu J L, Zhao H P, Dai Y H, Liu Q, Yang J, Jiang X W, Xu H F 2014 J. Semicond. 35 014004
[24] Gritsenko V A, Nekrashevich S S, Vasilev V V, Shaposhnikov A V 2009 Microelectr. Engineer. 86 1866
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