Abstract: When ion bombardment milling is used to each electronic devices having metal-polymer sandwich stuctures, the ion bombardment induces conductivity in the normally insulating polymer layers, even at low (e.g. 100 eV) bombardment energies. Bombarded polymer layers can be used to produce thin film resistors. Where it is desired to reduce or eliminate the bombardment induced conductivity, this may be accomplished, for a polyimide polymer, by a brief (e.g. 30 sec) exposure to a low energy (e.g.<10 eV) plasma, or by heating for a longer period of time (e.g 2 hours at 250.degree. C.), or by a combination thereof. It is desirable that the plasma contain oxygen.