An 8kB EEPROM-Emulation DataFLASH Module for Automotive MCU

An 8 kB E2FLASH test-chip is fabricated and reliability tests are executed. The paper shows the P/E cycle dependence of the threshold-voltage distribution and program/erase time. The threshold-voltage distribution does not degrade, and maintains enough margin to the wordline level (4.5 V) even after 1M P/E cycles. Erase time is 10 ms/block (average) for the first P/E cycle and 20 ms/block (average) after 1M P/E cycles. This is almost the same erase performance as on-board EEPROM, due to the DCNOR structure that does not use the read channel during program operation. On the other hand, program time increase is caused by charge trapping at tunnel oxide, but program time is 500 mus/word (average) even after 1M P/E cycles. The threshold-voltage shift value is only -1V after 1000 hr bake at Ta = 250 degC. These results indicate that the 8 kB E2FLASH is able to replace on-board EEPROM.