ELECTROPLATING OF CONDUCTIVE POLYMERS FOR THE METALLIZATION OF INSULATORS

Electrodeposition of copper was investigated on thin films of poly(3,4 -ethylenedioxythiophene) (PEDOT). This conducting polymer can be proce ssed from solution and exhibits a high specific conductivity of about 300 S/cm. N-(3-Trimethoxysilylpropyl)pyrrole was applied as a primer i n order to adhere PEDOT to the substrates. The lateral propagation or front velocity of the copper front and the uniformity of the copper de posit were determined as a function of sheet resistance of the PEDOT f ilms, type of PEDOT counterions, and of the temperature, applied poten tial and composition of the electrochemical baths. The experimental da ta obtained are interpreted using a simple mathematical model to descr ibe transient thickening during electrodeposition on electrodes of hig h ohmic resistance. A good agreement with experimental data is obtaine d, especially for the front velocity being inversely proportional to t he square root of the sheet resistance. Quantitative analysis of unifo rmity data shows that the affinity for nucleation is much higher on th e conducting polymer than on the deposited metal. This conclusion is s upported by activation energies as determined from temperature-depende nt metallization experiments. Finally, adhesion of copper deposits as a function of copper thickness and morphology of the substrate are dis cussed.