Fabrication of Silicon Nitride Film using Pure Nitrogen Plasma Generated near Atmospheric Pressure for III-V Semiconduct

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E11.23.1

Fabrication of Silicon Nitride Film using Pure Nitrogen Plasma Generated near Atmospheric Pressure for III-V Semiconductor Fabrication R. Hayakawa, T. Yoshimura, M. Nakae, T. Uehara1, A. Ashida, and N. Fujimura Department of Applied Materials Science, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan, E-mail: [email protected] 1 Sekisui Chemical Co. LTD., 32 Wadai, Tsukuba, Ibaraki 300-4292, Japan ABSTRACT Stable discharging of pure nitrogen can be maintained even at atmospheric pressure when alternative pulsed voltage is applied between two parallel plate electrodes. From optical emission spectroscopy, strong emissions from the N2 2nd positive system, weak emissions from N2 Herman’s infrared system and N2 1st positive system were observed. The emission intensities from the N2 2nd positive system and the N2 Herman’s infrared system increase with increasing the nitrogen gas pressure, whereas the emission intensities from the N2+ 1st negative system and N2 1st positive system decrease. The thickness of the silicon nitride film fabricated at 500 Torr was 1.6 nm at a nitridation temperature as low as 25ºC, regardless of the nitridation temperature and nitridation time. From these results, we conclude that N2 (C 3 Π u ) plays an important role for the excellent reactivity of the nitrogen plasma generated near atmospheric pressure.

INTRODUCTION Nitrogen plasma has been intensively studied due to the promising applications for the fabrication III-V nitride semiconductors1,2 such as GaN, AlN, and InN. Electron cyclotron resonance (ECR) plasma and radio frequency (RF) plasma sources are usually used and operated at the pressure ranging from 10-3 to 10 -6 Torr, which may yield the nitrogen defects in these nitrides. Therefore, we have tried to apply a nitrogen plasma generated near atmospheric pressure for III-V nitride semiconductor processes. However, it was very difficult to maintain the stable and non-equilibrium nitrogen plasma because the transition time from glow discharge to arc discharge drastically decreases with increasing the nitrogen pressure. Recently, some of our authors have developed the plasma source that maintains the stable discharge in pure nitrogen without helium at atmospheric pressure by applying the alternative pulsed voltage.3,4 In this study, as first step to apply for III-V nitride semiconductor processes, the nitridation of silicon wafer was performed. The reactivity of excited nitrogen species with silicon wafer using nitrogen plasma generated near atmospheric pressure is discussed. The dielectric properties of these films are also discussed.

E11.23.2

EXPERIMENT Nitrogen plasma was generated by applying an alternative pulse voltage ranging from 1 to 3 kV, a pulse width of 5 µsec and a frequency of 30 kHz between two parallel plate electrodes. High-purity nitrogen (99.9999 %) was flown at a flow rate ranging from 1.5 to 10 l/min. To reduce the impurities such as H2O and O2, an absorbing purifier (SAES Getters, FACILI TOR