Speed modulation technique to achieve simultaneous deposition of 3-in. double-sided Y-Ba-Cu-O thin films

We present a sputtering system which allows simultaneous deposition of high-Tc superconducting films on both sides of the substrates up to 3-in. diameter. In order to enhance the homogeneity of 3-in. thin films, a speed-modulated bi-axial rotation method has been introduced, by which the thickness deviation of 3-in. thin films is reduced to less than 5%. The crystalline structure and superconducting properties are measured. The full width at half maximum values of X-ray diffraction ω-scan on YBa2Cu3O7−δ (0 0 5) reflection are 0.15° and 0.21° for the center and the edge, respectively. The measured superconducting transition temperatures Tc range from 89.8 K to 90.2 K and the critical current densities jc mapped by jc-scan Leipzig system at 77 K, 0 T are about 2.1-2.5 MA/cm2. The majority of the wafer area has microwave surface resistances Rs (75 K, 145 GHz, 0 T) measured by confocal resonator in the range of 45-80 mΩ. The breakdown field demonstrating the high-frequency power handling capability is higher than 5 mT at 8.5 GHz and 77 K.