Pulsed High-Voltage Breakdown of Thin-Film Parylene C

Measurements of polymer dielectric high-voltage (HV) strength at thicknesses in the 1- to 10- μm range have always been difficult to validate and repeat. We report results of experiments done using parylene-C films of 2-, 4-, and 6- μm thicknesses in a series of configurations intended to determine the HV breakdown of the material itself with a minimum of externally undefined parameters. The experiments used an alumina substrate coated with a conductive gold film with a parylene-C film deposited on top of the lower gold film. One edge of the lower gold film was exposed to provide electrical connection, and a triangular or circular gold electrode was deposited on the surface of parylene C. The intent was to test the dielectric breakdown strength of bare parylene C, as well as to evaluate the effects of field enhancements produced by the two electrode shapes. Initial data analysis shows the presence of at least two regimens of electron transport at breakdown: 1) ohmic or “trap dominated” and 2) space charge or “trap free”.