Materials Challenges in Automotive Embedded Non-Volatile Memories

Abstract

Silicon-based nonvolatile memory modules are widely used in microcontrollers, where they are embedded into a monolithic system on a chip (SoC) which also includes high speed logic transistors, cache SRAM, and peripheral circuits for communicating with the external world. The physical principle most widely exploited for nonvolatile code and data storage is charge storage in floating gates. Charge storage in nitride traps, and more recently, in nanocrystals also has been explored.The most demanding use profiles with respect to temperatures, data retention times, and low failure rates are encountered in automotive engine control applications, where junction temperatures up to 150∞C are common, for 1000ís of hours. Starting with the 130nm technology node, embedded Flash technology has been integrated with copper interconnects, and at the 90nm node, low dielectric constant interlevel dielectrics are also employed to increase circuit performance. To achieve automotive reliability, the materials surrounding the silicon floating gate, nanocrystal, or nitride charge storage area must be evaluated for parasitic charge storage, write/erase stress-induced leakage current, and other parameters important for reliability. Any movement of parasitic charge, potentially over a long period of time, can reduce the sensing window of the Flash EEPROM bitcell.

Scalable processes for fabricating non-volatile memory devices using self-assembled 2D arrays of gold nanoparticles as charge storage nodes

“…reducing tunnelling oxide thickness and using high-k dielectrics, without compromising on reliability and endurance, 3 as there are formidable challenges associated with physical scaling of devices, such as cell-to-cell interference, poor reliability and lower gate coupling ratio. [3][4][5][6][7][8] The use of charge trapping layers, encased in a high-k dielectric, 9,10 as storage nodes is the most promising route to overcome these issues. 8 Charge trapping devices, comprising of either interface traps or nanoparticles as storage nodes have been studied for a long time, [11][12][13] especially for military and space applications due to their enhanced radiation tolerance.…”