Laser-enhanced patterning using photothermal effects: maskless plating and etching

Abstract

We review our work on laser-enhanced plating and etching with emphasis on the chemical, electrochemical, and thermal mechanisms giving rise to the experimental observations. The metallurgical properties of the deposits and their applications, particularly in the field of microelectronics, are also discussed. The work on laser-enhanced electroplating and electrodeless plating includes high-speed deposition of copper, gold, and nickel by using the argon-ion laser as the source of localized energy. Deposition rates up to 3 orders of magnitude higher have been observed for laser-irradiated regions compared with nonirradiated ones. Mechanisms responsible for the plating enhancement are (1) enhanced chemical and electrochemical kinetics with increased temperature, (2) shifts in the local rest potential with temperature, and (3) local agitation of the solution as a result of large temperature gradients. Applications of these techniques to circuit design and repair as well as to high-speed plating of precious metals onto electrical contact areas of microelectronic circuits are considered. Experiments on high-speed laser-enhanced etching of several dielectrics are also reviewed. Volume removal rates as high as 106μm3/sec for an alumina/TiC ceramic and 105μm3/sec for 〈111〉 silicon using KOH as the etchant have been obtained.