Self-healing breakdown of polyimide thin films in high temperature region - effect of curing temperature and polarity reversal on self-healing breakdown

摘要

In this study, the breakdown characteristics of polyimide thin films were measured by taking advantage of self healing breakdown with respect to the influence of curing temperature and the polarity reversal of polyimide. The curing of polyimide was performed at temperature of 120°C or 200°C. In both cases, electric strength (Fb) decreased with rising temperature. However, the values of Fb are more scaff ered at 120°C in comparison with those at 200°C. This is partly because the solvent was not removed enough during thermal treatment at 120°C, and has resulted in the variations in the measured Fb values. The effect of polarity reversal on Fb of polyimide thin film was examined at room temperature, 120°C and 200°C in dry air. At 200°C, Fb fell just after polarity reversal and gradually increased with the number of breakdowns. Based on this result, we conclude that the breakdowns were affected by the space charge formation. This process occurred repeatedly after the subsequent polarity reversal. At 20°C and 120°C the Fb remained same and did not change with polarity reversal. In this case we may conclude that there are few carrier injection from electrode in lower temperature region.