Flash: A “Forgotten” Technology in VLSI Design

Flash has been the workhorse technology for non-volatile memory design for many years now. In this chapter, we show that flash technology can be used to design a variety of general-purpose circuits, both digital and analog. We demonstrate this via case studies that demonstrate two styles of flash-based ASIC design (including a secure variant), flash-based convolutional neural network accelerators (both analog and digital variants), flash-based in-memory computing designs, as well as flash-based analog circuits like DACs and LDOs. Through these studies, we demonstrate several advantages of flash-based designs over conventional CMOS designs, and argue that flash is a “forgotten” technology. Some of these advantages are not present in CMOS, such as performance tunability, the ability to counteract circuit aging, the control of speed binning, and the ability to mitigate process variations. Based on our findings, we posit that the programmability, robustness, stability, and maturity of flash give it a significant edge over the class of “emerging” technologies, making flash a viable technology to eventually replace CMOS. There are certainly processing issues to be addressed to allow flash to scale to smaller process node geometries, but we hope that this chapter will encourage further research and deployment in this arena, allowing flash to become a key technology for digital and analog circuits in the future.