Embedded memory technologies: Present and future

MEMORIES CONTINUE TO be a key technology driver in the semiconductor industry. Advanced memory technologies are the trendsetters for integration levels and chip density. Over the past two decades, we have witnessed the on-chip integration of large cache memories as computer architects and chip designers have grappled with the challenges of high power consumption and the need to reduce memory access times. While on-chip SRAM is ubiquitous today, recent years have also seen the integration of embedded DRAM (eDRAM) and flash memory in commercial processor chips. A number of exciting new memory technologies are currently on the horizon for example, magnetic RAM (MRAM), resistive RAM (RRAM), phase-change RAM (PCRAM), and spin-transfer torque RAM (STT-RAM). These technologies offer a number of practical options for nonvolatile storage. Highdensity embedded memories will therefore become even more ubiquitous in newer technology generations as we move toward 3D integration. Embedded memories pose unique challenges to the circuit designer. Typical design challenges include reduced noise margins, susceptibility to coupling and signal marginality, and problems arising from device mismatch. There is clearly a close relationship between embedded memory design and the underlying process technologies. This timely special issue highlights the key features of today’s embedded memories and evaluates emerging memory technologies that can significantly influence the design of next-generation ICs. Guest Editors Chris Kim and Leland Chang have done a stellar job in putting together this special issue with seven selected articles by experts from both universities and industry. These articles cover research advances, practical experiences, and perspectives on future trends. The special issue includes perspectives from a visionary on technology evolution and emerging technology trends, articles from industry experts on SRAM and eDRAM, and coverage of emerging memories. Soon, revolutionary new applications such as wearable electronics, portable medical monitors, and implantable medical devices are likely to result from advances in these memory technologies. The authors of the articles in this special issue explain how design and technology challenges, along with process variations, can be overcome, and how we can design reliable embedded memories for high performance and low power consumption. This issue also includes an article that presents an overview of EDA standards, and examines the development and evolution of EDA standards worldwide. I thank Stan Krolikoski, chair of the IEEE Design Automation Standards Committee, for contributing this article. I am glad that we are able to bring you an update on standards activities, and we hope to make these reports a regular feature of D&T. I thank Chris and Leland for serving as guest editors of the special issue, the authors for their contributions, and the reviewers for their diligence and adherence to a tight review schedule. I wish all D&T readers a very happy and successful new year!