Scanning ultraviolet (UV) lasers would be used to expose ultraviolet-sensitive photoresists to form patterns of conductors for electronic circuits, according to a proposal. Heretofore, such patterns have been formed by exposing photoresists to collimated ultraviolet or visible light through contact or proximity photomasks. The use of scanning lasers would make it unnecessary to make or use masks, and it would be amenable to rapid fabrication of prototype circuits.
In forming a given circuit pattern, the scanning of the ultraviolet laser would be controlled by use of the same plotting data, generated by computer-aided-design software, that would otherwise have been used to plot the photomask for the pattern. In the case of a negative photoresist, the portion of the resist not exposed to the laser would be removed by a stripping compound after the photoresist had been developed. The metal underlying the exposed and stripped areas would be etched away. Then the remaining exposed photoresist would be stripped away.
In the case of a positive photoresist covering a very thin chromium-coated medium (insulating substrate), the part of the resist exposed by the laser would be removed by developing and stripping, then through the resulting openings in the resist, the desired electrically conductive material (typically, copper or gold) would be electrodeposited through the openings in the resist. Finally the unexposed resist and the thin chromium coat would be stripped from the medium.
This work was done by Frank Hartley and Steve Bolin of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Manufacturing & Prototyping category.