Projection optical lithography apparatus

Photocopying – Projection printing and copying cameras – With developing

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355 39, 355 45, G03B 2732, G03B 2752

Patent

active

043773397

ABSTRACT:
In a printed circuit formation process, a positive photoresist layer on a semiconductor substrate surface is exposed to light in a projection exposure system through a transparent liquid-gate which has an index of refraction n.sub.L closer to the index of refraction n.sub.R of the resist layer than is the index of refraction of air. This reduces reflection of light from the resist layers and thus minimizes standing waves in the layer, which waves produce a deleterious layered resist structure and require critical dependence of exposure time on absolute resist thickness. By using photo developer liquid in the gate as the index matching medium together with a reflex viewing system, visual monitoring of the expose/develop process in real time is realized.

REFERENCES:
patent: 3115815 (1963-12-01), Friedel

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