Maskless Lithography: Circa 1977

Summary : IBM’s EL-1: a milestone in e-beam lithography

Annexure :

This Electronics article marks a milestone that heralds the recurring dream that direct-write lithography using an electron beam would someday replace masks and optical lithography. In fact, Gordon Moore mentions this in his landmark 1965 article in the same publication from which, Moore’s Law would become known. Yet, e-beam never displaced optical despite many repeated attempts.

The spec’s of this system show just how good IBM research is as an institution. Achieving a square beam was a major breakthrough. Its registration accuracy was better than half that of any optical aligner in its day. It was needed to ensure lines could be stitched together. It may have been the first tool to have a vacuum load-lock for production.

Most important was its throughput of 22 wafers-per-hour, which brought IBM’s EL-1 closest to displacing optical. This was little different than then emergent wafer steppers and about half that of projection scanners.  

It’s always been believed that throughput was the main obstacle to maskless lithography.  This has not been the case, as systems that achieved production-worthy throughputs for their day were never successful past one or two nodes, obsoleted by increasing density.

IBM was the only company with the wherewithal to ever use maskless lithography in a production environment. It gave them the advantage of reduced spares inventory and quick-turn manufacturing decades before its time, while enabling legendary customer satisfaction with high uptime of systems in the field. IBM’s e-beam development was truly a wonder of the semiconductor world.

Today, Electronics no longer exists, a victim of the vicious silicon cycle. In its day, it was the most prestigious publication on electronics.

                                                                                                           - G. Dan Hutcheson

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