Beam-controlled processing will affect all areas of semiconductor and microelectronic fabrication and packaging. The dramatic expansion in the microelectronics industry has been the result, in part, of the development of higher levels of integration and circuit density. Smaller devices are required to maintain this progress. New lithography techniques utilizing photon, electron, or ion beams have led to the shrinking of the lateral feature size of a transistor to the submicrometer regime. Vertical device dimensions can be reduced even further to well below 0.1 μm through the use of epitaxial techniques. The advantages in fabrication afforded by these beam technologies will certainly justify the increased complexity and difficulties in their development. Meeting the challenges of these technologies will also open the door to new important physical phenomena useful in the next generation of information-processing machines.