Embedded HIMOS(R) flash memory in 0.35 μm and 0.25 μm CMOS technologies

In this paper, the performance and reliability characteristics of the 0.35 μm/0.25 μm High Injection MOS (HIMIOS(R)) technology is described in detail. This flash EEPROM technology relies on source-side injection for programming and Fowler-Nordheim tunneling for erasing, and has been successfully implemented in a 1 Mbit memory array embedded in a 0.35 μm CMOS technology, adding only about 30% to the processing cost of digital CMOS. Due to its triple gate structure, the HIMOS(R) cell exhibits a high degree of flexibility and scalability. A fast programming operation (10 μs) at 3.3 V supply voltage is combined with an endurance of well over 100000 program/erase cycles, immunity to all possible disturb effects and a retention time that largely exceeds 100 years at 125°C. Furthermore, the cell has been scaled to a 0.25 μm version, which is a laterally scaled version with the same operating voltages and tunnel oxide thickness. The use of secondary impact ionization is investigated as well and proves to be very promising for future generations when the supply voltage is scaled below 2.5 V