Name Competing Non Contact Approaches Considered

# Name Competing Non-Contact Approaches Considered

Projection was not the only non-contact idea explored to solve contact printing's defect problem; proximity printing, which held the mask a small fixed gap above the wafer without a full optical imaging system, was also tried.

Proximity printing reduced contact-driven defects somewhat but suffered diffraction-related image blur across its gap, since it lacked a true imaging optical path to correct for that spreading.

Full optical projection, as Micralign implemented it, solved the blur problem proximity printing could not, which is why projection rather than simple proximity became the production standard that followed contact printing.

NON-CONTACT ALTERNATIVES CONSIDEREDProximity printingmask held a small gap above the wafer, no imaging opticsLimitationdiffraction blur across the gap, uncorrectedFull projectionadds imaging optics to correct for this blur

Diagram above: non-contact alternatives considered.

WHY PROJECTION WON OUTProximity printingreduced contact risk, but still blurredProjection printingsolved both the contact problem and the blur problemOutcomeprojection, not simple proximity, became the production standard

Diagram above: why projection won out.

Take name competing non contact approaches considered further

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