Space-charge-limited currents in polyimide films

Space-charge-limited currents have been identified in thin polyimide film capacitor structures as the main conduction process in the very high temperature range from 320 degree C to 400 degree C before the breakdown. The transition field between the trap-filled-limit conduction and the trap-free conduction is reported versus temperature. Assuming an exponential distribution of the traps in the forbidden gap, both the characteristic temperature and trap energy are obtained at 446 degree C and 62 meV, respectively. The total trap density is accurately estimated at 1.5 1017 cm-3 using the Kumar approximation [Kumar , J. Appl. Phys. 94, 1283 (2003)]. Finally, the mobility temperature dependence of free charges is reported between 1.6 10-6 and 2.3 10-6 cm2 V-1 s-1 in the range from 340 degree C to 400 degree C.