There are many problems which should be solved before implementation of high $T_c$ superconducting oxide thin films to the microelectronics devices. These problems are: difficulties in film composition control; a long list of process parameters which affect the various properties of deposited films; relatively poor understanding of the relationships between film structure and the properties; and so on. In this respect, this study focuses on the atomic composition of fabricated Y-Ba-Cu-O thin films as a function of target to substrate distance (T/S-distance) and $O_2$ partial pressure of sputter gas mixture, and relationships among compositions, structures, and critical temperatures of the films.
The atomic compositions of the films were controlled through narrow gap RF-sputtering method and almostly reached to its ideal ratio, Y:Ba:Cu=1:2:3, when T/S-distance=10mm and sputter gas pressure=50mTorr, for the case of $YBa_{2.5}Cu_{4.5}O_x$ target. Two different substrates of $SrTiO_3$(100) and MgO(100) single crystal was chosen to investigate the effect of substrate on film characteristics. Microstructure of the films was characterized using optical microscope and SEM. Also EPMA was used to analyze atomic composition of the film surface. The superconductivity of the films showed $T_{\infty}=90~95K$, $T_{\infty}=70~75K$ with good reproducibility. The highest critical temperature obtained was 84K for $T_{\infty}$. For resistivity measurement, four probe method with thermally evaporated Au electrodes was adopted. Also the interactions between Y-BaCu-O thin films and $SiO_2$ or $Si_3N_4$ overlay were investigated.
