Increase of dielectric constant of an epitaxial (100) yttria-stabilized zirconia film on (100) Si substrate deposited by reactive sputtering in the metallic mode

A (100) heteroepitaxial yttria-stabilized zirconia (YSZ) film was prepared on a (100) Si substrate by dc magnetron sputtering with Ar + O-2 gas. In this case, we used the metallic mode, in which the target is almost metallic due to the low O-2 gas pressure and the sputtered metallic Zr and Y species around the substrate react with oxygen to be oxidized. The relative dielectric constant of the 10-nm-thick YSZ film deposited in the metallic mode was above 17, which is much larger than that obtained in the oxide mode, which is about 9. The oxide mode is normally used, in which the target surface is fully oxidized and the sputtering gas contains an excess amount of oxygen. The YSZ film deposited in the metallic mode was post-annealed at 300 degreesC in N-2 for 30 min. The equivalent silicon oxide thickness of the annealed YSZ film was estimated to be about 1.86 nm determined from the accumulation capacitance of the capacitance-voltage characteristics and its leakage current was less than 1 x 10(-4) A/cm(2) at 1 V.