HANABUSA Takao The University of Tokushima, Faculty of Engineering, Professor, 工学部, 教授 (20035637)
NAKABAYASHI Ichiro The University of Tokushima, Faculty of Engineering, Professor, 工学部, 教授 (70035624)
In this study, for the DC reactive sputtering process for nitrides and oxides, we investigated the influence of ions impinging the substrate on the film properties. Since sputtering system with two faced targets was expected to be effective in decreasing the film bombardment on the substrate by energetic ions, we applied this sytem in investigation of the influence of ion exposure of the substrate. In the film deposition of AlN,the influence of ion bombardment was not decreased even in the facing target sputtering system, and the film growth was degraded by the ion bombardment. The mechanism of acceleration of ions such as nitrogen and argon toward the substrate were cleared to be due to mainly by the potential difference between the plasma potential in discharge region and the floating potential on the substrate. The above influence of ion bombardment on the film was decreased by using alternating sputtering technique where one target was biased at positive potential while another tar
get was sputtered. The results demonstrated that the ion bombardment can be diminished by this sputtering system, which confirms the ion bombardment is taking an important role in the film quality of AlN film. Setting a mesh in front of the substrate also changed the ion flux bombarding the substrate, which influenced on the residual stress in AlN film. Magnetic field distribution in the facing target sputtering system influenced the ion flux bombarding the substrate. These characteristics were related to the electron and ion flow in the chamber, as a result, the ion flux bombarding the substrate.
In the deposition of oxides, we adopted ZnO film and ITO film. We could not obtain the 150-200 mu OMEGAcm resistivity in ZnO (the lowest value reported until now) only by decreasing energetic particles bombarding depositing film. Other factors were more important to acoomplish the lowest value in resistivity. We showed that additional Zn atoms have a strong influence in decreasing the film resistivity. Appropriate addition of Zn atoms improved the film crystallinity, and increased also the carrier concentration and the Hall mobility. This was caused by an increase of nuclei at the first stage in polycrystal film growth. In ITO deposition, we examined the effects of decreasing the energetic oxygen in using facing targets. Certainly we could obtain the lowest film resistivity by this technique. Furthermore, using (00・2) AlN as a substrate we could increase the carrier concentration, but the decrease of Hall mobility was observed. This was due to the increase of donor scattering. As a result, a drastic improvement in resistivity was difficult in ITO film. The improvement of doping efficiency of Sn donors is necessary for much more decrease in ITO film resistivity. Less