LOW-TEMPERATURE OXIDATION FOR GATE DIELECTRICS OF Poly-Si TFTs USING HIGH-DENSITY SURFACE WAVE PLASMA

摘要

Low temperature oxidation for gate dielectrics is a key technology for Poly-Si TFTs. Properties of SiO_2 films formed at lower than 400°C using surface wave plasma were studied. 4-nm-thick oxide grown by Kr-mixed oxygen plasma at 200°C had the O/Si ratio of 1.98. The ratio was smaller even at 350°C growth temperature when pure O_2 plasma was used. The activation energy of the parabolic rate constant was 0.08 eV for both the Kr-mixed and the pure O_2 plasma. These results indicate that the oxidants are the same in both cases. Meanwhile, electron density increased abruptly in a region of more than 90% concentration of Kr. Excited Kr and Kr ions were generated proportionally to the electron density. Based on these results, oxidation kinetics may be enhanced using the above species during oxidation with the Kr-mixed plasma.