A STUDY OF THE OXIDE GROWN ON WSI2

Modern single-poly electrically erasable programmable read-only memories (EEPROM) use a stacked silicide/polysilicon (polycide) floating gate as a charge storage element. In these devices the ability to retain stored charge relies on the quality of the top silicon dioxide, thermally grown on the silicide, which is known to be affected by the oxidation procedure. In this work we have studied silicon dioxide films, thermally grown in a dry oxygen atmosphere on WSi2, both in terms of composition and electrical properties. Concentration depth profiles were obtained by means of Auger electron spectroscopy (AES), while electrical characteristics were obtained on poly-Si/SiO2/WSi2 capacitors, from C-V plots, I-V measurements and ramped voltage stress. To characterize the oxide reliability, the endurance and memory retention at high temperature have been measured on single-poly EEPROM cells. The results show that the oxide thermally grown on tungsten silicide can meet the requirements for single-poly PROM device fabrication. The functionality of memory cells has been demonstrated, both with endurance and retention measurements.