A NEW PORTRAYAL OF OXIDATION OF UNDOPED POLYCRYSTALLINE SILICON FILMS IN A SHORT-DURATION

Abstract

Both polysilicon films low-pressure chemical-vapor-deposited (LPCVD) at 625 degrees C and amorphous films deposited at 550 degrees C with subsequent annealing at 600 degrees C for 24 h to form polysilicon films were used to grow polyoxides at 850 degrees C in wet or dry oxygen. Detailed high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) studies have been performed to determine the microstructures of the polyoxide/polysilicon interface and the crystallinity of the polysilicon films. It is found that the oxidation phenomena of these two films are very different. For the recrystallized amorphous silicon specimens, the polyoxide/polysilicon interface is very flat because of the poor crystallinity and low-angle grain boundaries between the grains. On the other hand, the polyoxide/polysilicon interface is rough for the as-deposited polysilicon samples due to the distinct grain characteristics and the high-angle grain boundaries between these grains.