Hidenori Mitani

7.6 A 90nm embedded 1T-MONOS flash macro for automotive applications with 0.07mJ/8kB rewrite energy and endurance over 100M cycles under Tj of 175°C

The computerization of automotive control has expanded the application range of micro controller units (MCUs). A high-end engine-control unit (ECU) requires high-performance Flash MCUs, which integrate high-speed CMOS logic and large high-performance embedded Flash memories (eFlash) [1,2]. There are also broad markets for motor control MCUs: used to control actuators in parts such as seats, windows, and mirrors. In order to integrate analog circuits to control the high voltage (HV) drivers in these parts, those MCUs have been manufactured in Flashless process, and external EEPROM chips are being used. EEPROM chips work as “learning memories” which store the calibration data to optimize analog circuit performance in the field. Replacement of external EEPROM chips by eFlash, resulting in less additional process cost and higher rewrite endurance, is a requirement for more elaborate learning at a higher data sampling rate. In addition to automotive grade reliability under extremely harsh temperature conditions, low power consumption is also a strong requirement as the number of MCUs used in motor control systems is increasing.

SONOS 1Tr eFlash Memory

In this chapter, a brief history of SONOS flash technology is introduced followed by the details of one-transistor SONOS (1Tr-SONOS) technology. Memory-cell structure, basic cell-operation principles and fabrication process are described. Then basic array architecture and read/program/erase operations are explained with corresponding peripheral circuits. A disturb mode in program and erase operations is also discussed. Finally, advanced circuit techniques to expand application range, especially for automotive use with high reliability and low energy consumption are described.