Effects of humidity on electric field distribution in polyimide insulation in microelectronics applications

With large scale integration in microelectronics, the thickness of insulation between closely spaced conductors at different potentials is reduced to the micrometer range and the electric field in the insulation becomes both a performance issue and a reliability issue. Using the thermal pulse method, we have measured for the first time the field distribution in 5 μm thick polyimide and found complex charging behaviour at ambient temperature and low field (circa 3 V/μm) representative of operating conditions. Field-independent charge layers are observed on the front surface in addition to injected charge extending deep into the bulk from the polyimide/substrate interface. These effects are considerably influenced by moisture uptake