Solid state UV-laser technology for the manufacture of high performance organic modules

Abstract

Advances in solid state laser technology have enabled tremendous performance increases in chip packaging technology. Organic composites are now available for high I/O flip chip modules due in part to the size, speed and flexibility of laser via creation methodologies. Generation of the third and fourth harmonics of the fundamental infrared Nd-YAG wavelength enable precision micromachining of alternating layers of organic insulators and metal conductors. The range of available pulse energies at high repetition rate, low M/sup 2/ values and superb pulse stability allows the formation of both high aspect ratio through vias and very small blind vias utilizing similar tools. The ability to fabricate chip packages with through vias, staggered blind vias, or any combination of blind, buried and through vias affords system and chip level design teams the maximum allowable flexibility to optimize performance versus cost. The most fundamental hardware improvements revolve around the conversion efficiency and power stability of Q-switched, lamp pumped Nd-YAG lasers utilizing BBO crystals for harmonic generation. The high pulse energies coupled with excellent beam quality translates into near theoretical focal depth values that in turn allow <50 micron, >7:1 aspect ratio interconnects to be manufactured at defect densities less than 50 ppm. Other advances including improved coatings on crystals and optics and improved thermal management at the rail, result in overall system availability exceeding 85% and via location accuracy of better than +/-20 microns. Future advances are likely to include a migration from lamp pumping to diode pumping, optimization of frequency conversion and laser design for greater power at high repetition rates, multi-rail systems and improved automation. A roadmap for past, current and future laser characteristics as they relate to via qualities and their relative costs will be discussed.