Reaction mechanism of selective plating between TiW and Au:An innovative metallization scheme for high-speed electronics

In our previous letter, we presented a novel fabrication process which allows us to form submicron gold interconnections with high aspect ratio. The process was made possible by selective electroplating which is an important key technique to build a submicron interconnection, particularly by a simple fabrication process. We found in our recent experiments that the “sheet resistance” difference, as mentioned in our previous letter, is not what makes the electroplating process selective. Through voltammetry measurements, it was found that much higher deposition potential is required for the oxidized TiW electrode than that for the Au electrode. We concluded that the difference in the “deposition potential” between metal and semiconducting electrodes is what makes the electro-plating pocess selective.