Self-healing breakdown of polyimide thin films in the cryogenic temperature region

Abstract

The breakdown characteristics of polyimide thin films were measured by taking advantage of self-healing breakdown in a wide temperature range. The electrical breakdown strength was nearly independent of temperature from 77 K to room temperature; it decreased with temperature in the high-temperature region. It showed little electrode-metal dependence at 77 K, but at room temperature, the A1 cathode indicated a lower breakdown strength than the Au cathode. From these results, the electronic breakdown process was considered as a possible breakdown mechanism in the cryogenic region, where only limited electronic-carrier injection from the electrode and thus little formation of space charges are expected. Although the breakdown strength retains nearly the same value after a polarity reversal at 77 K, in dry air at room temperature it fell just after the polarity reversal and gradually increased with the number of breakdowns.