As-Deposited Superconducting Y-Ba-Cu-0 Films on GaAs Substrate by High Pressure Dc Sputtering Process
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AS-DEPOSITED SUPERCONDUCTING Y-Ba-Cu-O FILMS ON GaAs SUBSTRATE BY HIGH PRESSURE DC SPUTTERING PROCESS R.J. Lin, Y.L. Lin, F.M. Pan and P.T. Wu Materials Research Laboratories, Industrial Technology Research Institute, 195 Chung-hsing Rd., Sec. 4, Chutung, Hsinchu 31015, Taiwan, R.O.C. ABSTRACT Superconducting Y-Ba-Cu-O thin films on (100)GaAs substrate have been successfully prepared by the high pressure DC sputtering process without further post-annealing treatment. The target was compound YjBa 2 Cu 3Ox made by solid-state reaction. The sputtering gas was Ar-50%02 , and total pressure was 1.5 torr. The substrate temperature was lower than 450*C. The best superconductivity of the film is Tc(onset) = 95K and Tc(R=O) = 40K. There are no microcracks on the film surface. The interdiffusion between the film and GaAs is limited. INTRODUCTION There has been a great deal of interest in fabrication of high-Tc superconducting thin films on semiconductor substrates, e.g., Si, Si0 2 and GaAs. A variety of new electronic applications would be created by combining superconductor and conventional semiconductor technology. Though the superconducting Y-Ba-Cu-O (YBCO) films can be grown on Si with buffer layers by high temperature annealing process[1], the low temperature process is more desirable for device applications due to compatibility with the current semiconductor technology and smooth film surface. There have been many reports [2-4] on preparation of superconducting YBCO films on Si at low substrate temperatures (5500 700 C). There are few on preparation of YBCO films on GaAs. In our previous papers [5-6], we reported a simple high pressure DC sputtering process to prepare as-grown superconducting YBCO thin film on Si, Si0 2 , GaAs, Cu/Ni and Cu/Ag substrates at temperatures lower than 450'C. In this paper, the detailed process and results of characterization of filmls on GaAs will be discussed. EXPERIMENTAL The YBCO films were prepared by the high pressure DC planar diode sputtering process from a compound target. The target (diameter 4.5cm; thickness 0.4cm) was made by a solid-state reaction of Y203, BaC03 and CuO in the stoichiometric ratio of Y:Ba:Cu = 1:2:3. The target was sintered at 930°C for 15 hr in air. The 3 base pressure of the vacuum system prior to deposition was 1x10- torr. The sputtering gas was Ar-50%02 , and total pressure was 1.5 torr. The target-to-substrate separation was 2cm. The substrate was (100)GaAs single crystal. The substrate was preheated to 380 0 C by IR quartz heater. The sputtering voltage and current was 230-240 volts and 0.8 amperes, respectively. The stable temperature of the substrate was about 430 0 C. The substrate temperature was measured by a K-type thermocouple, whose naked measuring head was held in close contact with the back of the substrate surface. The thickness of the films was Mat. Res. Soc. Symp. Proc. Vol. 169. @1990 Materials Research Society
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After deposition, 1-2pm and the deposition rate was 2-4A0 /sec. the gas ionization system and rotary vacuum pump were turned
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