The next generation non-volatile random-access memory cells

Significance 

Technological advances in the field of integrated circuits and semiconductors have led to the development of complementary metal oxide semiconductors (CMOS) with applications in numerous areas including memory devices. Currently, the design and development of non-volatile memory devices are based on current technologies. Alternatively, recent research has shown that numerous problems experienced today are mainly associated with heat, quantum uncertainties and costs of fabrication. As such, due to the physical limitations of the CMOS technologies, researchers have been looking for alternative ways of addressing the problems to develop future generation memory devices.

Consequently, in a recently published literature, resistive switching device has been identified as a promising non-volatile memory thus attracting significant attention of researchers. This is due to its high-density fabrication and capability to replace dynamic random-access memories. Among the available single bit based non-volatile memories, crossbar arrays have particularly demonstrated high-density integrations. Unfortunately, the high-power consumption and sneak current problems that lead to read errors have limited the use of crossbar arrays. Several approaches such as the incorporation of rectifying elements have been proposed to overcome the sneak current problem. Despite the remarkable achievement, more insight is still highly desirable.

To this note, Professor Jinho Bae at Jeju National University together with Professor Nobuhiko Kobayashi at the University of California Santa Cruz developed a new design parameter to perform an error analysis in passive crossbar arrays. Specifically, the sneak current problem was investigated by connecting the memory cell to a pair of row-column in either high resistance or low resistance depending on the stored logic value. The study is currently published in the journal, Semiconductor Science and Technology.

In brief, the research team initiated their work by a detailed cross-examination of the influence of the resistive switching behavior on the forward current flow in low resistance state and reverse current flow in the high resistance state along sneak current paths. Next, the ratio of the reverse low resistance state to forward low resistance state was maximized and its influence on the miss read error and sneak current investigated.

The authors observed minimal sneak currents in the resistive switches connected in reverse bias. This was attributed to the use of asymmetric memristors that fairly blocked the reverse current. On the other hand, maximizing the newly proposed parameter, that is, the ratio of reverse low resistance state to forward low resistance state also contributed significantly to minimizing the sneak currents. Furthermore, it was worth noting that the sneak current problem was more in large size arrays than small size arrays. This was, however, reduced by having the read current dominate the sneak current.

In summary, for commercialization of crossbar resistive switching arrays, Jinho Bae and Nobuhiko Kobayashi proposed two main design points to be taken into consideration. This includes the design parameter, reverse low resistance state to forward high resistance state ratio, and the read error bound. Altogether, the resistive switching devices is a promising solution for large scale design and production of high-performance non-volatile random-access memories.

Acknowledgment

The work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (NRF-2016R1A2B4015627).

The next generation non-volatile random-access memory cells - Advances in Engineering

About the author

Jinho Bae received his Ph.D. degree from Korea Advanced Institute of Science and Technology (KAIST), Daejeon, Republic of Korea, in 2001. During 1993 and 2002, he was a member of the technical staff at Daeyang Electric Co., Busan, Republic of Korea. During 2006 and 2007, he was a visiting scholar of electrical and computer engineering department of Texas A&M University, Collage Station, TX, USA. During 2013 and 2014, he was a visiting scholar of electrical engineering department of UCSC, Santa Cruz, CA, USA. Since 2002, he has been a faculty member in the Department of Ocean System Engineering at Jeju National University.

His current research interests include functional electronic polymeric materials, printed electronics, layer peeling problem, and optical signal processing.

About the author

Nobuhiko P. Kobayashi, a professor at the University of California Santa Cruz (UCSC), joined UCSC in 2008. Immediately after joining UCSC, Kobayashi served on the co-director of Advanced Studies Laboratories – a strategic partnership between UCSC and NASA Ames Research Center – for 3 years. Kobayashi currently oversees his laboratory, Nanostructured Energy Conversion Technology and Research (NECTAR) that focuses on basic and applied research in exploring exotic physical properties emerging from materials tailored at the length scale ranging from 10-9 m to 10-3 m. Target applications include harvesting, converting, storing, generating, and transmitting energy as well as cutting energy consumption by implementing new knowledge at material, device, and sub-system levels potentially offering resources required to drive just about every aspect of the rapidly emerging global economy. NECTAR also focuses on science and engineering required for a range of electronic materials that would benefit such disciplines as astronomy and marine biology through developing, for instance, advanced reflectors and protection coatings for ground-based and space telescopes and electrode materials used in electrolysis of saline water.

In the past ten years at UCSC, Kobayashi managed a range of projects supported by various U. S. federal agencies including Defense Advanced Research Program Agency, Office of Naval Research, Department of Energy, Advanced Research Project Agency – Energy, NASA, and National Science Foundation. Prior to joining UCSC, Kobayashi was involved in developing electronic materials for ultra-high-density electrical switches to build memories and logics required for future computing systems at Hewlett-Packard Laboratories. He was also involved in semiconductor nanowire photonics for optical interconnect necessary for advanced computing systems.

Prior to Hewlett-Packard Laboratories, Kobayashi worked at Lawrence Livermore National Laboratory, developing semiconductor materials for both ultra-high-speed diagnosis systems required for the National Ignition Facility funded by the U.S. Department of Energy and the optical code division multiple access (optical-CDMA) funded by Defense Advanced Research Project Agency. From 1999 to 2001, Kobayashi was at Agilent Laboratories, developing light emitting diodes, vertical cavity surface emitting lasers, and hetero bipolar transistors for both ultra-wide band fiber-optics and wireless communications.

Kobayashi published over 200 journal and conference papers, in addition, Kobayashi currently holds 23 U.S. patents. Kobayashi currently serves on program committee members/conference chairs/co-chairs at SPIE Energy Harvesting and Storage, SPIE Image Sensing Technologies, SPIE Optics and Photonics/Nanoscience and Engineering, and World Congress on Engineering and Computer Science. Kobayashi earned his M.S. and Ph.D. degrees in materials science from University of Southern California in 1994 and 1998, respectively.

Reference

Bae, J., & Kobayashi, N. (2019). Resistive switching device with highly-asymmetric current-voltage characteristics: its error analysis and new design parameter. Semiconductor Science and Technology, 34(2), 025007.

Go To Semiconductor Science and Technology

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