Device characteristics research according to the array EEPROM cell's active pattern difference

In the product development of our company's Deep Sub Micron Display Driver IC(DDI), we found that inner cell's and outer cell's characteristic are significantly different. This problem leads to device yield drop and reliability problem, so we must check the reason why the characteristics changes of inner cell and outer cell were so serious in the array EEPROM cell. First of all, we check the gate oxide area in EEPROM cell on the supposition that inner cell's and outer cell's gate oxide thickness are different. After we checked it, we found that the most effective reason of the characteristics changes was Gate Oxide Thickness changes had a decisive effect on the EEPROM Cell' changes according to the degree of STI profile(Top Corner Rounding). And the difference of STI profile is cause of active pattern difference. In this paper, we suggested the profile improvement method by STI process and characteristics improvement by insulting Dummy cell.