Session 8 – TAPA 1

RRAM I

Wednesday, June 13, 8:05 a.m.

Chairs: J. Zahurak, Micron Technology, Inc.

N. Kasai, Tohoku Univ.

8.1 - 8:05 a.m.

A Novel Cross Point One-Resistor (0T1R) Conductive Bridge Random Access Memory (CBRAM) with Ultra Low Set/Reset Operation Current, F.M. Lee, Y.Y. Lin, M.H. Lee, W.C. Chien, H.L. Lung, K.Y. Hsieh, C.Y. Lu, Macronix International Co., Ltd.

Using the dual Vth characteristics of a multi-layer HfO2/SiO2/Cu-GST conducting bridge (CB) structure we can construct a one-resistor cell without an access device (0T1R). Like 1T Flash memory the Vth is used to store the logic state thus leaving all devices always at high resistance state and a separate isolation device is not needed. The Vth of the cell is determined by the presence of CB in the HfO2 layer only. The CB in the SiO2 is present only temporarily during reading, and is spontaneously dissolved afterward. This spontaneous rupture of the filament in the SiO2 layer greatly reduces the switching current as well as reducing the read disturb. The mechanism for the spontaneous rupture phenomenon is investigated.

8.2 - 8:30 a.m.

Field-Driven Ultrafast sub-ns Programming in W\Al₂O₃\Ti\CuTe-Based 1T1R CBRAM System, L. Goux, K. Sankaran, G. Kar, N. Jossart, K. Opsomer, R. Degraeve, G. Pourtois, G.-M. Rignanese*, C. Detavernier**, S. Clima, Y.-Y. Chen, A. Fantini, B. Govoreanu, D.J. Wouters, M. Jurczak, L. Altimime, J. Kittl, imec, *UCL and ETSF, **University of Gent

We optimize a 90nm-wide CuTe-based 1T1R CBRAM cell for highly controlled and ultrafast programming by engineering Al2O3 electrolyte and Ti buffer layers of appropriate density and thickness resp. By means of electrical and ab initio modeling, we demonstrate that switching is mainly controlled by field-driven motion of Cu+ species. Sub-ns programming is allowed by strong ionic-hopping barrier reduction over short insulating gap. Complete picture of conductance and switching phenomenology is shown in the entire operation range.

8.3 - 8:55 a.m.

Multi-level Switching of Triple-layered TaOx RRAM with Excellent Reliability for Storage Class Memory, S.R. Lee, Y.-B. Kim, M. Chang, K.M. Kim, C.B. Lee, J.H. Hur, G.-S. Park, D. Lee, M.-J. Lee, C.J. Kim, U.-I. Chung, I.-K. Yoo, K. Kim, Samsung Advanced Institute of Technology

A highly reliable RRAM with multi-level cell (MLC) characteristics were fabricated using a triple-layer structure (base layer/oxygen exchange layer/barrier layer) for the storage class memory applications. A reproducible multi-level switching behaviour was successfully observed, and simulated by the modulated Schottky barrier model. Morevoer, a new programming algorithm was developed for more reliable and uniform MLC operation. As a result, more than 10^7 cycles of switching endurance and 10 years of data retention at 85C for all the 2 bit/cell operation were archieved.

8.4 - 9:20 a.m.

Conductive Filament Scaling of TaOx Bipolar ReRAM for Long Retention with Low Current Operation, T. Ninomiya, T. Takagi, Z. Wei, S. Muraoka, R. Yasuhara, K. Katayama, Y. Ikeda, K. Kawai, Y. Kato, Y. Kawashima, S. Ito, T. Mikawa, K. Shimakawa, K.Aono, Panasonic Corporation

We demonstrate for the first time that the density of oxygen vacancy in a conductive filament plays a key role in ensuring data retention. We achieve very good retention results up to 100 hours at 150˚C even under the low current operation due to the scaling of conductive filament size while retaining sufficiently high density of oxygen vacancy.

8.5 - 9:45 a.m.

Dynamic ‘Hour Glass’ Model for SET and RESET in HfO₂ RRAM, R. Degraeve, A. Fantini, S. Clima, B. Govoreanu, L. Goux, Y.Y. Chen, D. Wouters, P. Roussel, G.S. Kar, G. Pourtois, S. Cosemans, J. Kittle, G. Groeseneken, M. Jurczak, L. Altimime, IMEC

The set and reset process in HfO2 RRAM filament is modeled as a dynamic flow between two oxygen vacancy reservoirs connected by a narrow filament. The current is controlled by the width of the filament, that determines the electron transmission. The diffusion of oxygen vacancies is controlled by the local power in the filament. As a result, RESET is modeled as a dynamic balance between an upward and downward vacancy flow, while SET is modeled as an unbalanced filament growth bounded by the external compliance.