Browse Prior Art Database

Semitransparent Photomasks

IP.com Disclosure Number: IPCOM000076613D
Original Publication Date: 1972-Mar-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Anderson, LC: AUTHOR [+3]

Abstract

Photomasks useful for contact imaging of photosensitive media with ultraviolet light (e.g., KTFR* type photoresists) and for preexposure registration of the copy object under nonactinic lighting conditions are made by successively: 1) evaporating predetermined thickness of chrome upon alkali-free quartz substrate; 2) etching the chrome deposit (e.g., by electron beam) into the desired mask image configuration; 3) oxidizing the remaining chrome to Cr(2)O(3)(chromium oxide) in an air furnace (800 degrees C, 1-2 hours).

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Semitransparent Photomasks

Photomasks useful for contact imaging of photosensitive media with ultraviolet light (e.g., KTFR* type photoresists) and for preexposure registration of the copy object under nonactinic lighting conditions are made by successively: 1) evaporating predetermined thickness of chrome upon alkali-free quartz substrate;
2) etching the chrome deposit (e.g., by electron beam) into the desired mask image configuration; 3) oxidizing the remaining chrome to Cr(2)O(3)(chromium oxide) in an air furnace (800 degrees C, 1-2 hours).

A thickness of 1800 Angstroms of this chromium oxide is more durable and pin-hole free than a like thickness of plain chrome. It is also relatively opaque to light in the ultraviolet (UV) spectral range (actinic range of KTFR) and relatively transmissive in respect to nonactinic light in the visible range. Being also less reflective in the UV range than ordinary chrome the Cr O film has reduced fringe distortion effect in copying, since UV light reflected from the copy object surface is less subject to reflection back to the surface from the mask underside.

Deposition and etching of the chrome metal prior to its oxidation in step 2 above is convenient, since chrome metal is easier to etch than chromium oxide. * Product of Eastman Kodak Company.

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