Effect of applied field and temperature on the aging of copper discontinuous films studied by the repeated deposition technique

V. Damodara Das, M. S. Murali Sastry, M. Pattabi

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Presented are the results of investigations on the effect of an applied DC electric field on the post-deposition resistance changes of island copper films on glass. Based on the functional dependence of the film resistance on time, an agglomeration rate is defined with the theory of mobility coalescence being invoked to explain the resistance increase of the films after deposition. Repeated deposition was employed until the film resistance became steady, after which measurements of resistance versus temperature were made. The agglomeration rate for film of a particular resistance decreased as the number of deposition cycles was increased, due to formation of large, less mobile islands. For one of the higher-resistance films, the agglomeration rate showed a drastic fall for a particular value of deposition cycle number indicating that large-scale coalescence (LSC) had occurred. It was found that the presence of a field does not alter the post-deposition coalescence process in island copper films, possibly due to the relative immobility of the copper islands. The initial resistances of the film with and without the field were, however, vastly different. The agglomeration rates of films of different initial resistances showed an oscillatory behaviour corroborating earlier findings on copper films. The resistance-temperature curves showed a minimum below which the film showed a negative temperature coefficient of resistance (TCR) and a positive TCR above the temperature of transition. The transition temperature is found to shift to higher values as the films approach the discontinuous-semi-continuous structure transition. The resistance-temperature behaviour is explained if one considers that the negative TCR region is due to an increase in the number of thermally activated charged islands while the positive TCR region is due to enhanced mobility of the copper islands at elevated temperatures leading to coalescence and thus to an increase in the average inter-island spacing and the resistance of the film.

Original languageEnglish
Article number011
Pages (from-to)215-221
Number of pages7
JournalJournal of Physics D: Applied Physics
Issue number2
Publication statusPublished - 1987
Externally publishedYes

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