Implementation of Si nanocrystals in non-volatile memory devices




Growth in the demand for flash non-volatile memory (NVM) has been driven by mass storage applications, as well as mobile and consumer electronics. Embedded flash is utilized in microcontrollers where system speed, security, and customization are important. The challenges of embedded flash memories, usable across a range of products from consumer to automotive, include the ability to store and update data over a wide range of temperature and voltage corners. Nanocrystal memory is of great interest because of its improved reliability due to the localized nature of the charge storage, as well as its process simplicity and ease of integration into the complementary metal–oxide–semiconductor (CMOS) platform. Additionally, scaling of the dielectric thickness allows for reduced operating voltages and module size. Nanocrystal deposition techniques have been developed to produce uniform, controllable films, and device performance is well-behaved. The first commercially available microcontroller family built with silicon nanocrystals as the storage medium is now in production, built on a 90 nm platform and using a split-gate architecture. In this work, device and materials issues related to silicon nanocrystal memory are reviewed, and memory array performance discussed. Finally, scalability of nanocrystal memories is considered, where excellent performance and reliability can be achieved down to the 40 nm technology node and further.