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 90nm 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 40nm technology node and further.

We present the first-ever commercially available microcontroller families built with innovative split-gate based NOR flash memory that uses silicon nanocrystals as the storage medium. The 32-bit mixed-signal low-power Kinetis microcontroller families have nanocrystal based flash memories (referred to as TFS for `Thin Film Storage') with a wide range of array sizes from 32KB to 1MB. In addition, the unique capability of TFS has enabled inclusion of fully configurable embedded EEPROM functionality called `FlexMemory', which also manages wear leveling for high endurance. The TFS memory has been optimized to deliver read access time of <;30ns, fast source-side injection programming (10-20μs), fast tunnel erase into the gate (1-20ms), robust high temperature data retention before and after cycling, endurance of at least 10K cycles for flash and effective endurance up to 10M cycles in the EEPROM mode. In addition, the microcontroller core, analog and flash modules have been developed to deliver performance, reliability, and low-power operations across a temperature range of -40C to 105C and full operation down to 1.7V from a single power supply.

In June 2010, Freescale introduced the Kinetis product family of ARM ® -core based 32-bit microcontrollers (MCUs) built on the 90nm TFS (Thin Film Storage) embedded flash technology. That was the first time a flash technology based on the silicon nanocrystals as the storage medium was ever productized - fully 14 years after Tiwari introduced the concept of nanocrystal memory [1]. This paper describes the TFS technology, the architecture, the special features, the robustness, and the extendibility to 40nm and beyond.

This paper reports on recent bitcell optimizations that improve drive current and program performance. The 16 Mb and 32 Mb array results are best to-date for nanocrystal memories and suggest a robust, reliable array operation.

In this paper, the authors present the performance characteristics of such a silicon nanocrystal split gate bitcell and report an optimal bitcell process and integration scheme for memory arrays.