Wet Chemical Etching of High T C Superconductors by Ethylenediaminetetraacetic Acid (EDTA)
- PDF / 263,517 Bytes
- 4 Pages / 420.48 x 639 pts Page_size
- 109 Downloads / 182 Views
WET CHEMICAL ETCHING OF HIGH T, SUPERCONDUCTORS BY ETHYLENEDIAMINETETRAACETIC ACID (EDTA) F. K. Shokoohi, L M. Schiavone, C. T. Rogers, A. Inam*, X. D. Wu*, L Nazar, and T. Venkatesan Bellcore; 331 Newman Springs Road, Red Bank, NJ 07701 * Rutgers University, Piscataway, NJ 08854
ABSTRACT A novel chemical etchant for the high temperature superconducting material YBa 2 Cu3 O 7- 1 is demonstrated. The etching solution which consists of ethylenediaminetetraacetic acid (EDTA) in water does not degrade the properties of the superconducting films and is suitable for applications with standard photolithography. We have etched 2-200 pim wide wires which show no degradation of T, ( within 1 K accuracy of the measurements) and show zero-resistance temperature ->90 K. The etchant exhibits a polishing effect by selectively removing the porous and semiconducting surface layers which are formed during high temperature annealing process. The dense bulk of the films are etched at a rate of 1400 A/min which provides control for fine-line patterning of thin film material. The critical current densities of the unpatterned films which are polished b) reactions with EDTA remain unaffected and are measured to be about 5 x 106 A/cm INTRODUCTION During the past two years considerable effort has been directed towards preparation of high temperature superconducting ceramics.[1 ] Presently high quality films as thin as few hundred angstroms, with transition temperatures higher than 90 0K, can be prepared routinely. High critical current densities, Jc, however, have been more difficult to achieve, but thin films with Jc's on the order of 106 A/cm 2 at 77 K are now routinely deposited on perovskite-like substrates (e.g. SrTiO 3 , LaGaO3 , LaAIO 3, etc.) by deposition techniques such as pulsed-laser-evaporation which uses high quality bulk targets.[2l An important factor in future application of these high quality films in microelectronics is having the processing techniques which are suitable for use with these ceramic materials, particularly the ability to pattern the films for microfabrication of devices. Although , dry etching techniques, such as ion-milling,[31 focused-ion-beam etching,141 and reactive-ion-beam etching[51 provide precise etching, however, the electrical properties of the patterns are often degraded, and the mask materials are simultaneously eroded and modified due to partial decomposition during etching. Consequently to get masking materials which show dry etch resistance and the highresolution capability, which can be readily removed, leaving the highly reactive superconductor films unaffected is a major challenge. The reactivity of the standard photoresist, on the other hand, with most organic solutions, and extremely high etch rates of the superconductors experienced with inorganic etchants,[61 have made it difficult to apply standard wet photolithographic techniques for fine-line patterning of these ceramics. Mat. Res. Soc. Symp. Proc. Vol. 169. @1990 Materials Research Society
1300
We present a wet chemical etch w
Data Loading...
