Laser-enhanced plating and etching for microelectronic applications

The author describes the use of lasers to obtain patterns using plating and etching techniques. The enhanced rates result from accelerated electrochemistry and mass transport of the electrolytic solutions resulting from local heating produced by laser absorption at the workpiece-electrolyte interface. Examples of laser electroplating include results for nickel, copper, and gold with rates as high as ~1-5 μm/s. This is ~3 orders of magnitude higher than conventional electroplating rates. Similarly, high rates of electro-etching have been observed, particularly for such metals as stainless steel. Several applications of this technique are described, particularly as they pertain to VLSI circuit boards and connectors. A recent modification of the laser plating technique combines a laser with a high-velocity jet of electrolyte to obtain still higher rates of deposition. This scheme is described in some detail for gold and copper plating with observed rates as high as 20 and 50 μm/s, respectively, for the two metals.