Self-compliance-improved resistive switching using Ir/TaO x /W cross-point memory
© Prakash et al.; licensee Springer. 2013
Received: 5 November 2013
Accepted: 5 December 2013
Published: 17 December 2013
Resistive switching properties of a self-compliance resistive random access memory device in cross-point architecture with a simple stack structure of Ir/TaO x /W have been investigated. A transmission electron microscope and atomic force microscope were used to observe the film properties and morphology of the stack. The device has shown excellent switching cycle uniformity with a small operation of ±2.5 V and a resistance ratio of >100. The device requires neither any frorming-process nor current compliance limit for repeatable operation in contrast to conventional resistive random access memory devices. The effect of bottom electrode morphology and surface roughness is also studied. The improvement is due to the enhanced electric field at the nanotips in the bottom electrode and the defective TaO x switching layer which enable controlled filament formation/rupture. The device area dependence of the low resistance state indicates multifilament formation. The device has shown a robust alternating current endurance of >105 cycles and a data retention of >104 s.
KeywordsRRAM Cross-point TaO x Self-compliance
Resistive random access memory (RRAM) is the most promising candidate for the next-generation nonvolatile memory technology due to its simple structure, excellent scalability potential (<10 nm), long endurance, high speed of operation, and complementary metal-oxide-semiconductor (CMOS) process compatibility[1–7]. RRAM in cross-point architecture, in which top and bottom electrodes are placed at right angle to each other, is very attractive as it offers high-density integration with 4 F2, F being the minimum feature size area; three-dimensional (3D) stacking; and cost-effective fabrication[8, 9]. Switching uniformity is one of the important properties which require practical realization of cross-point devices with large array size. So it is necessary to investigate the factors affecting switching uniformity. Various binary transition metal oxides such as HfO x [5, 6, 10–12], TiO x [13, 14], TaO x [2, 7, 15–18], AlO x [19–21], ZrO x [22–24], WO x , etc. as a switching material are reported for RRAM application. Among them, recently, TaO x has attracted much attention owing to its superior material and switching properties such as having two stable phases, high thermal stability, small difference between the free energies of low and high resistance states, CMOS compatibility, long endurance, and high switching speed. So far,a cross-point resistive switching memory device in an Ir/TaO x /W structure has not yet been reported.
In this study, self-compliance-limited and low-voltage-operated resistive switching behaviors with improved switching cycle uniformity in a simple resistive memory stack of Ir/TaO x /W in cross-point architecture are reported. The physical properties of switching stack and bottom electrode morphology have been observed by transmission electron microscope (TEM) and atomic force microscope (AFM) analyses. The improvement is due to the defective switching layer formation as well as the electric field enhancement at the nanotips observed in the bottom electrode surface which results in controlled and uniform filament formation/rupture. The self-compliance property shows the built-in capability of the device to minimize the current overshoot during switching in one resistance (1R) configuration. The device has shown an alternating current (ac) endurance of >105 cycles and a data retention of >104 s.
Results and discussion
Improvement in the resistive switching and self-compliance behaviors of a forming-free resistive memory stack of Ir/TaO x /W in a cross-point structure has been obtained. The cross-sectional TEM image confirms the amorphous TaO x /WO x film. The AFM image shows the presence of nanotips on the W bottom electrode surface. The device has shown excellent switching uniformity during 100 consecutive dc sweeps with set/reset voltages of ±2.5 V and a resistance ratio of >100. The self-compliance behavior which comes from the bulk resistance of the stack shows the built-in capability of the device to minimize current overshoot during switching. The improvement in the switching is attributed to the formation of a defective switching layer and bottom electrode surface morphology with nanoscale tips which can enhance the electric field resulting in the uniform formation/rupture of the oxygen vacancy conducting filament. The device has exhibited an ac cycle endurance of >105 cycles and a data retention of >104 s. It is expected that this self-compliance, low-voltage-operated cross-point resistive memory device could be useful for the development of future nanoscale nonvolatile memory devices.
This work was supported by the National Science Council (NSC), Taiwan, under contract number NSC-102-2221-E-182-057-MY2.
- Waser R, Aono M: Nanoionics-based resistive switching memories. Nat Mater 2007, 6: 833. 10.1038/nmat2023View Article
- Lee MJ, Lee CB, Lee D, Lee SR, Chang M, Hur JH, Kim YB, Kim CJ, Seo DH, Seo S, Chung UI, Yoo IK, Kim K: A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O5−x/TaO2−xbilayer structures. Nat Mater 2011, 10: 625. 10.1038/nmat3070View Article
- Liu Q, Sun J, Lv H, Long S, Yin K, Wan N, Li Y, Sun L, Liu M: Real-time observation on dynamic growth/dissolution of conductive filaments in oxide-electrolyte-based ReRAM. Adv Mater 1844, 2012: 24.
- Park J, Lee W, Choe M, Jung S, Son M, Kim S, Park S, Shin J, Lee D, Siddik M, Woo J, Choi G, Cha E, Lee T, Hwang H: Quantized conductive filament formed by limited Cu source in sub-5 nm era. In Proceedings of the 2011 IEEE International Electron Devices Meeting (IEDM): Dec 5–7 2011; Washington, DC. Piscataway: IEEE; 2011:63.
- Govoreanu B, Kar GS, Chen Y, Paraschiv V, Kubicek S, Fantini A, Radu IP, Goux L, Clima S, Degraeve R, Jossart N, Richard O, Vandeweyer T, Seo K, Hendrickx P, Pourtois G, Bender H, Altimime L, Wouters DJ, Kittl JA, Jurczak M: 10×10nm2 Hf/HfO x crossbar resistive RAM with excellent performance, reliability and low-energy operation. In Proceedings of the 2011 IEEE International Electron Devices Meeting (IEDM): Dec 5–7 2011; Washington, DC. Piscataway: IEEE; 2011:729.
- Lee HY, Chen YS, Chen PS, Gu PY, Hsu YY, Wang SM, Liu WH, Tsai CH, Sheu SS, Chiang PC, Lin WP, Lin CH, Chen WS, Chen FT, Lien CH, Tsai MJ: Evidence and solution of over-RESET problem for HfO x based resistive memory with sub-ns switching speed and high endurance. In Proceedings of the 2010 IEEE International Electron Devices Meeting (IEDM): Dec 6–8 2010; San Francisco. Piscataway: IEEE; 2010:460.
- Strachan JP, Torrezan AC, Medeiros-Ribeiro G, Williams RS: Measuring the switching dynamics and energy efficiency of tantalum oxide memristors. Nanotechnology 2011, 22: 505402. 10.1088/0957-4484/22/50/505402View Article
- Baek IG, Kim DC, Lee MJ, Kim HJ, Yim EK, Lee MS, Lee JE, Ahn SE, Seo S, Lee JH, Park JC, Cha YK, Park SO, Kim HS, Yoo IK, Chung UI, Moon JT, Ryu BI: Multi-layer cross-point binary oxide resistive memory (OxRRAM) for post-NAND storage application. In Proceedings of the IEEE International Electron Devices Meeting, 2005. IEDM Technical Digest: Dec 5–7 2005; Washington, DC. Piscataway: IEEE; 2005:750.View Article
- Jiale L, Wong HSP: Cross-point memory array without cell selectors—device characteristics and data storage pattern dependencies. IEEE Trans Electron Devices 2010, 57: 2531.View Article
- Lee HY, Chen PS, Wang CC, Maikap S, Tzeng PJ, Lin CH, Lee LS, Tsai MJ: Low-power switching of nonvolatile resistive memory using hafnium oxide. Jpn J Appl Phys 2007, 46: 2175. 10.1143/JJAP.46.2175View Article
- Chen YY, Goux L, Clima S, Govoreanu B, Degraeve R, Kar GS, Fantini A, Groeseneken G, Wouters DJ, Jurczak M: Endurance/retention trade-off on HfO2/metal cap 1T1R bipolar RRAM. IEEE Trans Electron Devices 2013, 60: 1114.View Article
- Yu S, Chen HY, Gao B, Kang J, Wong HSP: HfO x -based vertical resistive switching random access memory suitable for bit-cost-effective three-dimensional cross-point architecture. ACS Nano 2013, 7: 2320. 10.1021/nn305510uView Article
- Yang JJ, Pickett MD, Li X, Ohlberg DAA, Stewart DR, Williams RS: Memristive switching mechanism for metal/oxide/metal nanodevices. Nat Nanotechnol 2008, 3: 429. 10.1038/nnano.2008.160View Article
- Kim KM, Choi BJ, Lee MH, Kim GH, Song SJ, Seok JY, Yoon JH, Han S, Hwang CS: A detailed understanding of the electronic bipolar resistance switching behavior in Pt/TiO2/Pt structure. Nanotechnology 2011, 22: 254010. 10.1088/0957-4484/22/25/254010View Article
- Yang JJ, Zhang MX, Strachan JP, Miao F, Pickett MD, Kelley RD, Medeiros-Ribeiro G, Williams RS: High switching endurance in TaO x memristive devices. Appl Phys Lett 2010, 97: 232102. 10.1063/1.3524521View Article
- Ninomiya T, Wei Z, Muraoka S, Yasuhara R, Katayama K, Takagi T: Conductive filament scaling of TaO x bipolar ReRAM for improving data retention under low operation current. IEEE Trans Electron Devices 2013, 60: 1384.View Article
- Prakash A, Maikap S, Chiu HC, Tien TC, Lai CS: Retraction: Enhanced resistive switching memory characteristics and mechanism using a Ti nanolayer at the W/TaO x interface. Nanoscale Res Lett 2013, 8: 419. 10.1186/1556-276X-8-419View Article
- Chen C, Song C, Yang J, Zeng F, Pan F: Oxygen migration induced resistive switching effect and its thermal stability in W/TaO x /Pt structure. Appl Phys Lett 2012, 100: 253509. 10.1063/1.4730601View Article
- Lin CY, Wu CY, Hu C, Tseng TY: Bistable resistive switching in Al2O3memory thin films. J Electrochem Soc 2007, 154: G189. 10.1149/1.2750450View Article
- Wu Y, Yu S, Lee B, Wong P: Low-power TiN/Al2O3/Pt resistive switching device with sub-20 μA switching current and gradual resistance modulation. J Appl Phys 2011, 110: 094104. 10.1063/1.3657938View Article
- Banerjee W, Rahaman SZ, Prakash A, Maikap S: High-κ Al2O3/WO x bilayer dielectrics for low-power resistive switching memory applications. Jpn J Appl Phys 2011, 50: 10PH01. 10.7567/JJAP.50.10PH01View Article
- Wang SY, Lee DY, Tseng TY, Lin CY: Effects of Ti top electrode thickness on the resistive switching behaviors of rf-sputtered ZrO2memory films. Appl Phys Lett 2009, 95: 112904. 10.1063/1.3231872View Article
- Liu Q, Long S, Wang W, Tanachutiwat S, Li Y, Wang Q, Zhang M, Huo Z, Chen J, Liu M: Low-power and highly uniform switching in ZrO2-based ReRAM with a Cu nanocrystal insertion layer. IEEE Electron Device Lett 2010, 31: 1299.
- Li Y, Long S, Lv H, Liu Q, Wang Y, Zhang S, Lian W, Wang M, Zhang K, Xie H, Liu S, Liu M: Improvement of resistive switching characteristics in ZrO2film by embedding a thin TiO x layer. Nanotechnology 2011, 22: 254028. 10.1088/0957-4484/22/25/254028View Article
- Chien WC, Chen YR, Chen YC, Chuang ATH, Lee FM, Lin YY, Lai EK, Shih YH, Hsieh KY, Chih-Yuan L: A forming-free WO x resistive memory using a novel self-aligned field enhancement feature with excellent reliability and scalability. In Proceedings of the 2010 IEEE International Electron Devices Meeting (IEDM): Dec 6–8 2010; San Francisco. Piscataway: IEEE; 2010:440.
- Prakash A, Jana D, Maikap S: TaOx-based resistive switching memories: prospective and challenges. Nanoscale Res Lett 2013, 8: 418. 10.1186/1556-276X-8-418View Article
- Prakash A, Maikap S, Banerjee W, Jana D, Lai CS: Impact of electrically formed interfacial layer and improved memory characteristics of IrO x /high-κ x /W structures containing AlO x , GdO x , HfO x , and TaO x switching materials. Nanoscale Res Lett 2013, 8: 379. 10.1186/1556-276X-8-379View Article
- Prakash A, Maikap S, Lai CS, Tien TC, Chen WS, Lee HY, Chen FT, Kao MJ, Tsai MJ: Bipolar resistive switching memory using bilayer TaO x /WO x films. Solid State Electron 2012, 72: 35.View Article
- Huang YC, Tsai WL, Chou CH, Wan CY, Hsiao C, Cheng HC: High-performance programmable metallization cell memory with the pyramid-structured electrode. IEEE Elecron Device Lett 2013, 34: 1244.View Article
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