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Reversible Photosensitive Masking Media for Semiconductor Photolithography

IP.com Disclosure Number: IPCOM000035820D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Fredericks, EC: AUTHOR

Abstract

Through the utilization of a mixture of appropriate materials, a method of masking several photolayers of a semiconductor, a printed circuit board or a packaging substrate with one photo mask is achieved.

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Reversible Photosensitive Masking Media for Semiconductor Photolithography

Through the utilization of a mixture of appropriate materials, a method of masking several photolayers of a semiconductor, a printed circuit board or a packaging substrate with one photo mask is achieved.

By incorporating photochromic properties into a semiconductor photo mask, one mask is useful for deep ultraviolet (UV), middle UV, far UV, infrared (IR) and X-ray transmittance exposure. Photochromic glass is an optical quality borosilicate composition containing a dispersion of light-sensitive silver halide crystals. These crystals are responsible for the unique property of variable light transmission, darkening in the 220 to 405 nanometer (UV) range and clearing in the 700 to 1200 nanometer (infrared) range, depending upon the composition of the glass. Some compositions have a cleared transmittance of up to 90%, while others exhibit a darkened transmittance of as low as 5%. Most importantly, the cycle is reversible and will not fatigue with time.

To fabricate a mask with photochromic properties, a quartz mask blank is coated with resist and etched to form holes 1.5 to 3.0 millimeters in depth, as shown in Fig. 1. The etched holes are then filled with a powdered glass/silver halide mixture and heated to cause the mixture to flow. Note that the mixture melt temperature is well below that of quartz. When used as a photomask in the deep UV exposure range, as shown in Fig. 2, the area of the...