SiO2 or Cu-doped SiO2 (Cu:SiO2) insulating films combined with Cu or W upper electrodes were constructed on the W/Si substrates to form the conductive-bridging RAM (CB-RAM) cells. The CB-RAMs were then subjected to a constant-voltage stressing (CVS) at room temperature. The experimental results show that the room-temperature CVS treatment can effectively affect the current conduction behavior and stabilize the resistive switching of the memory cells. After the CVS, the current conduction mechanisms in the high resistance state during the set process of the Cu/Cu:SiO2/W cell can be changed from Ohm’s law and the space charge limited conduction to Ohm’s law, the Schottky emission, and the space charge limited conduction. Presumably, it is due to the breakage of the conduction filaments during the CVS treatment that the conduction electrons cannot go back to the back electrode smoothly. 1. Introduction As the charge storage memory is approaching its scaling limit [1], the next generation nonvolatile memory (NVM) technologies have been widely investigated in recent years. New types of NVMs include the resistive random access memory (RRAM), magnetic random access memory (MRAM), and the phase-change random access memory (PRAM). The conductive-bridging RAM (CB-RAM) is one of the RRAMs within which metal cations, such as copper or silver, can form conductive bridges or break the conduction filaments between the top and the bottom electrodes via ion migration. The CB-RAMs can be switched between the high resistance state (HRS) and the low resistance state (LRS) under different bias polarities [2, 3]. The insulating materials between the active electrode (e.g., Cu or Ag) and the inert electrode (e.g., W or Pt) play important roles in the resistive switching (RS) operation and are called the solid electrolytes. Several kinds of the insulating materials, such as chalcogenide [4, 5], oxide-based [6–9], carbide [10], and amorphous silicon [11], have been used for the CB-RAMs. Among these materials, SiO2-based films have advantages such as simple composition, no toxicity, compatibility with the COMS technology, and low cost. In addition, most of the resistive switching improvement works of the RRAMs were done at elevated temperatures [12–14]. There is no room-temperature process of Cu doping in oxide found in the literature. This work has tried to develop the room-temperature process of Cu doping into oxide following the constant-voltage stressing (CVS) treatment for the RRAM application. In this work, improvement on the switching characteristics of the SiO2-based
References
[1]
C.-Y. Lu, K.-Y. Hsieh, and R. Liu, “Future challenges of flash memory technologies,” Microelectronic Engineering, vol. 86, no. 3, pp. 283–286, 2009.
[2]
Y. Bernard, V. T. Renard, P. Gonon, and V. Jousseaume, “Back-end-of-line compatible conductive bridging RAM based on Cu and SiO2,” Microelectronic Engineering, vol. 88, no. 5, pp. 814–816, 2011.
[3]
I. Valov, R. Waser, J. R. Jameson, and M. N. Kozicki, “Electrochemical metallization memories—fundamentals, applications, prospects,” Nanotechnology, vol. 22, no. 25, Article ID 254003, pp. 289502–289524, 2011.
[4]
S. Z. Rahaman and S. Maikap, “Low power resistive switching memory using Cu metallic filament in Ge0.2Se0.8 solid-electrolyte,” Microelectronics Reliability, vol. 50, no. 5, pp. 643–646, 2010.
[5]
L. Goux, K. Opsomer, R. Degraeve et al., “Improvement of CBRAM resistance window by scaling down electrode size in pure-GeTe film,” Applied Physics Letters, vol. 99, pp. 120–122, 2011.
[6]
C.-J. Li, S. Jou, and W.-L. Chen, “Effect of Pt and Al electrodes on resistive switching properties of sputter-deposited Cu-doped SiO2 Film,” Japanese Journal of Applied Physics, vol. 50, Article ID 01BG08, pp. 1–4, 2011.
[7]
Y. Bernard, P. Gonon, and V. Jousseaume, “Resistance switching of Cu/SiO2 memory cells studied under voltage and current-driven modes,” Applied Physics Letters, vol. 96, no. 19, Article ID 193502, pp. 1–3, 2010.
[8]
Y. Tsuji, T. Sakamoto, N. Banno, H. Hada, and M. Aono, “Off-state and turn-on characteristics of solid electrolyte switch,” Applied Physics Letters, vol. 96, no. 2, Article ID 023504, pp. 1–3, 2010.
[9]
K. Tsunoda, Y. Fukuzumi, J. R. Jameson, Z. Wang, P. B. Griffin, and Y. Nishi, “Bipolar resistive switching in polycrystalline TiO2 films,” Applied Physics Letters, vol. 90, no. 11, Article ID 113501, pp. 1–3, 2007.
[10]
H. Choi, M. Pyun, T.-W. Kim et al., “Nanoscale resistive switching of a copper-carbon-mixed layer for nonvolatile memory applications,” IEEE Electron Device Letters, vol. 30, no. 3, pp. 302–304, 2009.
[11]
S. H. Jo, K.-H. Kim, and W. Lu, “High-density crossbar arrays based on a Si memristive system,” Nano Letters, vol. 9, no. 2, pp. 870–874, 2009.
[12]
S. P. Thermadam, S. K. Bhagat, T. L. Alford, Y. Sakaguchi, M. N. Kozicki, and M. Mitkova, “Influence of Cu diffusion conditions on the switching of Cu-SiO2-based resistive memory devices,” Thin Solid Films, vol. 518, no. 12, pp. 3293–3298, 2010.
[13]
Y. Bernard, V. T. Renard, P. Gonon, and V. Jousseaume, “Back-end-of-line compatible conductive bridging RAM based on Cu and SiO2,” Microelectronic Engineering, vol. 88, no. 5, pp. 814–816, 2011.
[14]
C. Schindler, S. C. P. Thermadam, R. Waser, and M. N. Kozicki, “Bipolar and unipolar resistive switching in Cu-doped SiO2,” IEEE Transactions on Electron Devices, vol. 54, no. 10, pp. 2762–2768, 2007.
[15]
F.-C. Chiu, H.-W. Chou, and J. Y.-M. Lee, “Electrical conduction mechanisms of metal/La2O3/Si structure,” Journal of Applied Physics, vol. 97, no. 10, Article ID 103503, pp. 1–5, 2005.
[16]
F.-C. Chiu, “Electrical characterization and current transportation in metal/Dy2O3/Si structure,” Journal of Applied Physics, vol. 102, no. 4, Article ID 044116, pp. 1–5, 2007.
[17]
F.-C. Chiu, P.-W. Li, and W.-Y. Chang, “Reliability characteristics and conduction mechanisms in resistive switching memory devices using ZnO thin films,” Nanoscale Research Letters, vol. 7, article 178, pp. 1–9, 2012.
[18]
C. H. Kim, Y. H. Jang, H. J. Hwang, C. H. Song, Y. S. Yang, and J. H. Cho, “Bistable resistance memory switching effect in amorphous InGaZnO thin films,” Applied Physics Letters, vol. 97, no. 6, Article ID 062109, pp. 1–3, 2010.
[19]
Y. C. Yang, F. Pan, F. Zeng, and M. Liu, “Switching mechanism transition induced by annealing treatment in nonvolatile Cu/ZnO/Cu/ZnO/Pt resistive memory: from carrier trapping/detrapping to electrochemical metallization,” Journal of Applied Physics, vol. 106, no. 12, Article ID 123705, pp. 1–5, 2009.
[20]
K. M. Kim, B. J. Choi, Y. C. Shin, S. Choi, and C. S. Hwang, “Anode-interface localized filamentary mechanism in resistive switching of TiO2 thin films,” Applied Physics Letters, vol. 91, no. 1, Article ID 012907, pp. 1–3, 2007.
[21]
C. Chen, F. Pan, Z. S. Wang, J. Yang, and F. Zeng, “Bipolar resistive switching with self-rectifying effects in Al/ZnO/Si structure,” Applied Physics Letters, vol. 111, no. 1, Article ID 013702, pp. 1–6, 2012.
