- Nano Express
- Open Access
Retention Model of TaO/HfO x and TaO/AlO x RRAM with Self-Rectifying Switch Characteristics
© The Author(s). 2017
- Received: 9 February 2017
- Accepted: 1 June 2017
- Published: 13 June 2017
A retention behavior model for self-rectifying TaO/HfO x - and TaO/AlO x -based resistive random-access memory (RRAM) is proposed. Trapping-type RRAM can have a high resistance state (HRS) and a low resistance state (LRS); the degradation in a LRS is usually more severe than that in a HRS, because the LRS during the SET process is limited by the internal resistor layer. However, if TaO/AlO x elements are stacked in layers, the LRS retention can be improved. The LRS retention time estimated by extrapolation method is more than 5 years at room temperature. Both TaO/HfO x - and TaO/AlO x -based RRAM structures have the same capping layer of TaO, and the activation energy levels of both types of structures are 0.38 eV. Moreover, the additional AlO x switching layer of a TaO/AlO x structure creates a higher O diffusion barrier that can substantially enhance retention, and the TaO/AlO x structure also shows a quite stable LRS under biased conditions.
- TaO/HfO x
- TaO/AlO x
- Resistive memory
Because NAND flash technology is facing a scaling limit, vertical resistive random-access memory (VRRAM) designs with low film stacks, high manufacturing yields, and no cross-coupling problems are promising candidates for high-density memory applications [1–3]. The 1TnR architecture with three-dimensional (3D) vertical structure helps realize ultralow bit cost for highly compact dense arrays [4–6]. Several researchers have proposed operating RRAM at low current levels by changing the resistance switching mechanism from a filamentary-type to a defect-trapping-, vacancy-modulating-, or interface-type conducting path model [7–9]. However, the questions central to retention failures and the migration of oxygen vacancies are still unsolved [3, 10]. In some filamentary-type retention studies, many different models have been proposed to explain retention losses [11–13]. The change of switching mechanism also indicates a different direction that might improve retention . Our previous studies have shown that TaO/HfO x devices can show favorable nonlinearity values of approximately 40, endurance values exceeding 1000 cycles, and 85 °C data retention [6, 7]. Nevertheless, to obtain stable retention at such low operating current levels is still challenging. In this letter, a retention model is proposed to realize the retention loss in two different defect-trapping-type devices with the Arrhenius method. The extracted activation energy does not convincingly explain the retention improvement by the AlO x layer. Even though the original was ambiguous, the most likely interpretation is that dense bonding facilitates retention.
In summary, we compared two types of self-rectified RRAM devices through their switch characteristics and analyzed their retention behaviors. The TaO/AlO x device showed a higher switching voltage and a more robust LRS thermal stability than the TaO/HfO x device did. The benefit of robust retention from the AlO x switching layer is due to the high oxygen diffusion barrier rather than activation energy. The activation energy of retention loss is related to the ion de-trap process in the TaO resistive layer. The high atomic density of AlO x film may improve LRS retention. A retention loss schematic model has been proposed and the on-bias retention results supported this model. This model could be beneficial for the development of low-current, long-retention, self-rectifying RRAM devices for future high-density memory applications.
This manuscript was edited by the Wallace Academic Editing.
The authors declare that they have no competing interests.
YDL, KHT, WSC, and CHH fabricated the RRAM devices on 8-in. wafer under the instruction of PHW. YDL measured the devices under the instruction of SZR, HYL, and CJL. YSC also measured the devices. PSC, CJL, and YCK contributed to the understanding of the retention characteristics. YDL wrote the first draft, and the final draft was modified by PHW, SZR, and CJL. All the authors contributed to the preparation and revision of the manuscript, and they approved the final draft for publication.
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- Baek IG, Park CJ, Ju H, Seong DJ, Ahn HS, Kim JH, Yang MK, Song SH, Kim EM, Park SO, Park CH, Song CW, Jeong GT, Choi S, Kang HK, Chung C (2011) Realization of vertical resistive memory (VRRAM) using cost effective 3D process. Int Electron Devices Meet 31.8.1. doi:10.1109/IEDM.2011.6131654.
- Park SG, Yang MK, Ju H, Seong DJ, Lee JM, Kim E, Jung S, Zhang L, Shin YC, Baek IG, Choi J, Kang HK, Chung C (2012) A non-linear ReRAM cell with sub-1 μA ultralow operating current for high density vertical resistive memory (VRRAM). Int Electron Devices Meet 20.8.1. doi:10.1109/IEDM.2012.6479084.
- Ielmini D (2016) Resistive switching memories based on metal oxides: mechanisms, reliability and scaling. Semicond Sci Technol 31:063002View ArticleGoogle Scholar
- Zhang L, Cosemans S, Wouters DJ, Govoreanu B, Groeseneken G, Jurczak M (2013) Analysis of vertical cross-point resistive memory (VRRAM) for 3D RRAM design. Int Memory Workshop :1–4. doi:10.1109/IMW.2013.6582122.
- Chen HY, Yu S, Gao B, Huang P, Kang J, Wong HSP (2012) HfOx based vertical resistive random access memory for cost-effective 3D cross-point architecture without cell selector. Int Electron Devices Meet ᅟ:20.7.1–20.7.4. doi:10.1109/IEDM.2012.6479083.
- Lin YD, Chen YS, Tsai KH, Chen PS, Huang YC, Lin SH, Gu PY, Chen WS, Chen PS, Lee HY, Rahaman SZ, Hsu CH, Chen FT, Ku TK (2015) Highly robust self-compliant and nonlinear TaOx/HfOx RRAM for 3D vertical structure in 1TnR architecture. Intl Symp VLSI Tech Sys and App. doi:10.1109/VLSI-TSA.2015.7117559 Google Scholar
- Chen YS, Lee HY, Chen PS, Chen WS, Tsai KH, Gu PY, Wu TY, Tsai CH, Rahaman SZ, Lin YD, Chen F, Tsai MJ, Ku TK (2014) Novel defects-trapping TaOx/HfOx RRAM with reliable self-compliance, high nonlinearity and ultra-low current. IEEE Electron Dev Lett 35:202–204View ArticleGoogle Scholar
- Govoreanu B, Crotti D, Subhechha S, Zhang L, Chen YY, Clima S, Paraschiv V, Hody H, Adelmann C, Popovici M, Richard O, Jurczak M (2015) a-VMCO: a novel forming-free, self-rectifying, analog memory cell with low-current operation, nonfilamentary switching and excellent variability. VLSI Technology Symposium 59:T132–T133Google Scholar
- Prakash A, Jana D, Maikap S (2013) TaOx-based resistive switching memories: prospective and challenges. Nanoscale Res Lett 8:418View ArticleGoogle Scholar
- Subhechha S, Govoreanu B, Chen Y, Clima S, Meyer KD, Houdt JV, Jurczak M (2016) Extensive reliability investigation of a-VMCO nonfilamentary RRAM: relaxation, retention and key differences to filamentary switching. IEEE Int Reliab Phys Symp :6C.2.1–C6.2.5. doi:10.1109/IRPS.2016.7574568.
- Choi S, Lee J, Kim S, Lu WD (2014) Retention failure analysis of metal-oxide based resistive memory. Appl Phys Lett 105:113510View ArticleGoogle Scholar
- Yu S, Chen YY, Guan X, Wong HSP, Kittl JA (2012) A Monte Carlo study of the low resistance state retention of HfOx based resistive switching memory. Appl Phys Lett 100:043507View ArticleGoogle Scholar
- Chen CY, Fantini A, Goux L, Degraeve R, Clima S, Redolfi A, Groeseneken G, Jurczak M (2015) Programming-conditions solutions towards suppression of retention tails of scaled oxide-based RRAM. Int Electron Devices Meet :10.6.1–10.6.4. doi:10.1109/IEDM.2015.7409671.
- Chen YS, Lee HY, Chen PS, Lin YD, Tsai KH, Hsu CH, Chen WS, Tsai MJ, Ku TK, Wang PH (2016) Low power/self-compliance of resistive switching elements modified with a conduction Ta-oxide layer through low temperature plasma oxidization of Ta thin film. Intl Symp VLSI Tech Sys and App. doi:10.1109/VLSI-TSA.2016.7480496 Google Scholar
- Nardi F, Larentis S, Balatti S, Gilmer DC, Ielmini D (2012) Resistive switching by voltage-driven ion migration in bipolar RRAM—part I: experimental study. IEEE Electron Dev Lett 59:2461–2467View ArticleGoogle Scholar
- Maikap S, Jana D, Dutta M, Prakash A (2014) Self-compliance RRAM characteristics using a novel W/TaOx/TiN structure. Nanoscale Res Lett 9:292View ArticleGoogle Scholar
- Jana D, Samanta S, Roy S, Lin YF, Maikap S (2015) Observation of resistive switching memory by reducing device size in a new Cr/CrOx/TiOx/TiN structure. Nanoscale Res Lett 7(4):392–399View ArticleGoogle Scholar
- Ielmini D, Nardi F, Cagli C, Lacaita AL (2010) Size-dependent retention time in NiO-based resistive-switching memories. IEEE Electron Dev Lett 31:353–355View ArticleGoogle Scholar
- Chen YY, Komura M, Degraeve R, Govoreanu B, Goux L, Fantini A, Raghavan N, Clima S, Zhang L, Belmonte A, Redolfi A, Kar GS, Groeseneken G, Wouters DJ, Jurczak M (2013) Improvement of data retention in HfO2/Hf 1T1R RRAM cell under low operating current. Int Electron Devices Meet 10.1.1–10.1.4. doi:10.1109/IEDM.2013.6724598.
- Clima S, Chen YY, Degraeve R, Mees M, Sankaran K, Govoreanu B, Jurczak M, Gendt SD, Pourtois G (2012) First-principles simulation of oxygen diffusion in HfOx: role in the resistive switching mechanism. Appl Phys Lett 100:133102View ArticleGoogle Scholar
- Oishi Y, Kingery WD (1960) Self-diffusion of oxygen in single crystal and polycrystalline aluminum oxide. Journal of Chemical Physics 33:480View ArticleGoogle Scholar
- Zafar S, Jagannathan H, Edge LF, Gupta D (2011) Measurement of oxygen diffusion in nanometer scale HfO2 gate dielectric films. Appl Phys Lett 98:152903View ArticleGoogle Scholar
- Zhong X, Rungger I, Zapol P, Nakamura H, Heinonen YAO (2016) The effect of a Ta oxygen scavenger layer on HfO2-based resistive switching behavior: thermodynamic stability, electronic structure, and low-bias transport. Phys Chem Chem Phys 18:7502–7510View ArticleGoogle Scholar
- Traoré B, Blaise P, Vianello E, Grampeix H, Jeannot S, Perniola L, Salvo BD, Nishi Y (2015) On the origin of low-resistance state retention failure in HfO2-based RRAM and impact of doping/alloying. IEEE Tran Electron Devices 62:4029–4036View ArticleGoogle Scholar
- Traoré B, Blaise P, Vianello E, Grampeix H, Bonnevialle A, Jalaguier E, Molas G, Jeannot S, Perniola L, DeSalvo B, Nishi Y (2014) Microscopic understanding of the low resistance state retention in HfO2 and HfAlO based RRAM. Int Electron Devices Meet 21.5.1–21.5.4. doi:10.1109/IEDM.2014.7047097.