Low-temperature formation of gate-sio2 films for poly-si tfts by o2-ar sputtering

High-quality gate-oxide films for poly-Si TFTs are obtained successfully by oxygen-argon sputter deposition at low temperature (200°C). SiO2 films deposited in an oxygen-argon mixture on poly-Si have higher resistivities and breakdown fields than those deposited only in argon and thermal oxides grown on poly-Si, resulting in the same film characteristics as thermal oxides grown on single-Si. Moreover, poly-Si TFT mobilities are improved considerably by mixing oxygen, resulting in very high mobility of 383 cm2/V · s. This high mobility is caused by reduction in SiO2/Si interface states and in barrier heights at the poly-Si grain boundaries in addition to the improvement of poly-Si films. These characteristic improvements result from migration enhancement of sputtering particles on film surface and the reduction of plasma damage by oxygen mixture. These results confirm the usefulness of gate-oxide films sputter-deposited in an oxygen-argon mixture for low-temperature fabrication of high-quality poly-Si TFTs.