Method for making thermochromic photomasks
AssigneeDrexler Technology Corporation
InventorJerome Drexler
Life of this patent
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Abstract
An orange colored photomask visually transmissive to yellow-orange light formed by heating an exposed and developed silver-halide emulsion coated photomask. At approximately 200.degree. C., black silver in the photomask begins to show evidence of conversion to a transparent red material. At a temperature of 250.degree. C. to 320.degree. C., the black silver opaque images are rapidly converted to orange, visually transmissive images which are essentially opaque to the ultraviolet light used to expose photoresist covered silicon wafers, while clear areas remain clear.
Claims22
A method for making a photomask having silver and non-silver areas with said silver areas visually transmissive to yellow-orange light and opaque to ultraviolet radiation, the non-silver areas transparent to visible light and ultraviolet radiation comprising,
- producing a photomask pattern by exposing to actinic radiation and developing an image pattern in a silver-halide emulsion on a photoplate with resulting silver and non-silver areas,
- heating said emulsion to a temperature within a 250.degree. C. to 320.degree. C. range for 10 seconds to 3 minutes until such time as the silver areas become visually transmissive to yellow-orange light and the gelatin of the non-silver areas remains essentially clear.
A method for making a photomask having silver and non-silver areas with said silver areas visually transmissive to yellow-orange light and opaque to ultraviolet radiation, the non-silver areas transparent to visible light and ultraviolet radiation, comprising,
- producing a photomask pattern by exposing to actinic radiation and developing an image pattern in a silver-halide emulsion on a photoplate with resulting silver and non-silver areas,
- heating said emulsion until the transmissivity of said emulsion in the silver areas is increased by at least a factor of 20 for light at 630 nanometers and the gelatin of the non-silver areas remains essentially clear.
Dependencies are inferred from the claim text.