A composite process for eprom and eeprom and its reliability

Abstract

A process to form an IC with an EPROM (erasable programmable ROM) and EEPROM (electrically erasable PROM) was a developed and a module was tested. Fabricating a floating‐gate type EEPROM and the process to achieve high reliability in write/erase performance and the high data‐retention characteristic were investigated. The write/erase endurance is higher when the tunnel oxidation is carried out by wet oxidation than when carried out by dry oxidation. As the temperature for forming the inter‐polyoxide increases, the leakage current decreases but the write/erase endurance decreases. As the tunnel oxide film becomes thinner, the write/erase endurance decreases. The passivation layer has a great influence on the Vth window and data‐retention characteristics. When the passivation layer is a P‐SiN, the foregoing characteristics are poorer than when a PSG film is used. However, if PSG and P‐SiO films are formed under the P‐SiN film, the degradation of the forementioned characteristics decreases.