Improving program/erase endurance by controlling the inter-poly process in flash memory

Using poly-Si gate MOS capacitors, the tunnel oxide degradation due to high electric field stress is shown to be accelerated by the oxidation of the Si/sub 3/N/sub 4/ film in inter-poly ONO films and by high-temperature annealing. Microscopic Raman spectroscopy confirms that increased tensile stress in poly-Si gates leads to tunnel oxide degradation, Therefore, using CVD-SiO/sub 2/ film as the top oxide in inter-poly ONO films or using only a CVD-SiO/sub 2/ film as the inter-poly film, and reducing the high-temperature annealing time after poly-Si gate formation, will significantly increase the program/erase endurance of flash memory.