EXCELLENT EMISSION CHARACTERISTICS OF TUNNELING OXIDES FORMED USING ULTRATHIN SILICON FILMS FOR FLASH MEMORY DEVICES

A novel technique using oxidized ultrathin rugged polysilicon films on silicon substrates has been appied to significantly improve the tunne ling efficiency of thin oxides. As compared with oxidized amorphous si licon films, these rugged polysilicon films can achieve a higher emiss ion current. High-resolution transmission electron microscopy (HRTEM) was used to observe the atomic-scale microtips at the SiO2/Si and poly silicon/SiO2 interfaces. According to the extracted geometry parameter s of the microtips, a two-dimensional numerical simulator based on the finite difference method using the curved emitting surface of microti ps can well explain the remarkable current asymmetry of the dielectric s. This suggests that the oxidized rugged polysilicon films can form h igher microtips and smaller tip angles, resulting in better emission c haracteristics that will enable potential applications to future 5-V-o nly nonvolatile memories.