Use of Si-YBaCuO Intermixed System for Patterning of Superconducting Thin Films
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USE OF Si-YBaCuO INTERMIXED SYSTEM FOR PATTERNING OF SUPERCONDUCTING THIN FILMS Q. Y. MA, E. S. YANG, G. V. TREYZ, C. SHU, R. M. OSGOOD. Jr, AND CHIN-AN CHANG* Microelectronics Sciences Laboratories and Center for Telecommunications Research, 1312 Mudd, Columbia University, New York, NY 10027 *IBM T. J. Watson Research Center, Yorktown Heights, NY 10598 ABSTRACT A Si-YBaCuO intermixed system has been formed using rapid thermal annealing (RTA) of Cu/BaO/Y2O,/Si layered structures, which were deposited on MgO substrates by electron-beam evaporation. The electrical and structural properties of the Si-YBaCuO system have been analyzed by resistivity, X-ray diffraction, scanning electron microscope, X-ray photoelectron spectroscopy and Auger depth profiling measurements. It was found that Si mixed with YBaCuO during annealing, thus creating an insulating film. This effect has been used to pattern YBaCuO films. The patterning process was carried out on an underlying silicon layer, rather than the YBaCuO film itself, using conventional photolithography or laser etching. After YBaCuO film deposition and RTA, the patterned region became superconducting separated by Si-YBaCuO intermixed areas. Micron-sized line features with T,'s above 77 K have been demonstrated. INTRODUCTION The discovery of the high temperature superconductors (HTS) [I] has brought a new class of materials with some unique characteristics to electronic applications. To utilize this material as a workable electronic device or component, many technical problems have to be solved. First, a thin film of this material must be formed. Second and more importantly, the film needs to be patterned to desired device features. Over the last three years, many deposition techniques have been developed for making HTS thin films. However, the patterning of these films still relies on conventional processes such as wet chemical methods [2-5] or the sue of laser ablation [6-8]. The former method involves removal of material using chemical solutions, which may degrade the superconductor surface. The laser ablation while promising, still remains to be fully proven. We have found that some impurities introduced into an YBaCuO film destroy the superconductivity of the film. A typical example is the Si-YBaCuO intermixed system. When YBaCuO film is mixed with silicon during a high temperature annealing, the film becomes nonsuperconducting; in fact, it is a perfect insulator. In this work, we present studies of the structural and electrical properties of the Si-YBaCuO intermixed system. We report the development of a novel HTS patterning technique using the Si-YBaCuO intermixed system. Both micron-sized lines and large-scale device features are demonstrated using this technique. The smallest line patterned was 2 um in width and it showed zero resistance at 77K. This method provides a chemical free way of patterning HTS films. Mat. Res. Soc. Symp. Proc. Vol. 169. ©1990 Materials Research Society
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PROPERTIES OF THE Si-YBaCuO INTERMIXED SYSTEM The sample preparation includes e
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