Method of eliminating gate leakage in nitrogen annealed oxides

摘要

The improvement of thin tunnel oxides used in EEPROM and FLASH tecnologies using post-oxidation annealing in nitrogen causes defects in subsequent oxide films. These are manifested by oxide thinning at the bird's beak and result in high gate leakage. As the time and temperature to the post-oxidation annealing are increased for improved tunnel oxide performance, the number of defects increases rapidly. A method of realizing the improved tunnel oxide QBD using higher post-oxidation time and temperature annealing while at the same time not degrading the quality of subsequent gate oxides is shown. The use of sacrificial oxidation and strip just prior to the transistor gate oxidation is described. This process removes the additional nitride which exists at the field edges, leading to the oxide thinning. As a result, improved tunnel oxide integrity can be achieved without degradation of high and low voltage transistors.