Abstract

Mask-projection systems are widely used in excimer laser machining such as viahole drilling for printed circuit boards. However, a large part of the laser-beam power is lost on the mask, because the open areas of masks are ordinarily very small. A more efficient method is machining with holograms. CO₂ or Nd:YAG laser machining with holograms that directly generate patterns has been reported since the 1970s.^1-3 For excimer lasers, because of their low spatial coherence, it is difficult to generate patterns directly with holograms.

© 1996 Optical Society of America