Emerging Nanoelectronic Devices

25Storage Class Memory

Geoffrey W. Burr¹ and Paul Franzon²

¹IBM, USA

²North Carolina State University, USA

25.1 Introduction

One challenge in computing systems is the need for new memory technologies that can improve overall performance. More and more frequently, the ability of a CPU to rapidly execute programs is being limited by the rate at which data can arrive at the processor. Unfortunately, scaling does not automatically solve this problem. One evolutionary solution has been to increase the size of cache memory and thus the floor space that SRAM occupies on a CPU chip. However, this trend eventually leads to a decrease of the net information throughput.

While DRAM offers higher density than SRAM, auxiliary circuitry is required to maintain the stored data. True nonvolatility has conventionally required external storage media (e.g., magnetic Hard Disk Drives (HDDs), optical CDs, etc.), with access times that are slower than the volatile memory by many orders of magnitude. Solid-State Disks (SSDs) based on NAND Flash have recently offered nonvolatility at significantly lower latencies than HDDs, but are block-based, much slower to erase than to program, and offer fairly poor cycle endurance.

The development of an electrically accessible nonvolatile memory with high speed, high density, and high endurance, referred to as “Storage Class Memory” or SCM, would initiate a revolution in computer architecture. By using CMOS-compatible fabrication technology scaled beyond the present ...