Prospects and Challenges of Next-Generation Flash Memory Devices
School of Advanced Materials Engineering, Kookmin University Seoul 136-702, Korea
We can divide the history of memory devices in terms of their applications. From the latter half of the 1980’s, personal computers were the major application area, and in that regime, DRAM was the dominant memory device. However, since latter half of the 1990’s, the use of mobile electronic devices, such as MP3 players, digital still cameras, personal digital assistants, cellular phones, etc., has increased greatly, making flash memory devices the most widely used form of memory. The rapid progress in this field has been quite beyond expectations.1-5 However, we now face very difficult challenges inherent in the development of NAND flash memory devices with a 20 nm design rule. Further, scaling predicts that memory devices with feature sizes down to 10 nm should be developed in just a few years. It is not clear how this will be achieved. For now, lithography advances have made it possible to use optical lithography tools to define 30 nm features and thanks to this, we can develop 10+ Gb memory devices without resorting to nonoptical lithography, such as EUV, electron-beam, or x-ray.
In addition to the rapidly advancing technology, the sales of flash memory devices are also very encouraging. Since 2005, NAND flash revenues have surpassed those for NOR flash and NAND will continue to be a leading player in ...