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Thin Film Dosimetry

IP.com Disclosure Number: IPCOM000045332D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 3 page(s) / 28K

Publishing Venue

IBM

Related People

Hatzakis, M: AUTHOR [+2]

Abstract

It has been found that a very large amount of triphenylmethane nitrile dye can be dissolved in copolymers and/or terpolymers of polymethyl methacrylate and methacrylic acid dissolved in methyl CELLOSOLVE Trademark of Union Carbide Corporation), from which very thin dosimeter films can be formed.

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Thin Film Dosimetry

It has been found that a very large amount of triphenylmethane nitrile dye can be dissolved in copolymers and/or terpolymers of polymethyl methacrylate and methacrylic acid dissolved in methyl CELLOSOLVE Trademark of Union Carbide Corporation), from which very thin dosimeter films can be formed.

Triphenylmethane nitrile dye derivatives (shown below) change color as a function of absorbed ionizing radiation (<3400 Angstroms) and have been described by Chalkley (1) for use as a dosimeter by incorporating these dyes in paper and polymer films.

Further work has been done by Huett (2) and McLaughlin, et al. (3), in improving the polymer/dye combinations, and recently commercial films (50 Mum thick) have been marketed. Today, the main application for these commercial films is for dose measurement in the food and wire-coating industries. While these films are useful for some lithographic applications, such use is limited because of the large thickness of such films, thickness variations, and difficulty in applying the films to supporting substrates. We describe here a method of forming thin dosimeter films (1 Mum) in a new polymer system and new applications for these films.

To date, the maximum solubility of radiochromic dyes in a polymer matrix been limited to about 2-15%. Consequently, thick films (50-100 Mum) are needed to achieve a suitable optical density change. It has been found that by incorporating a radiochromic dye, specifically hexahydroxyethyl paraosaniline nitrile into a polymer matrix consisting if a copolymer of polymethyl methacrylat4e and methacrylic acid (20-35 wt. percent) dissolved in methyl CELLOSOLVE, it is possible to load the polymer with 50% (by wt.) of the dye. A thin film spun on a quartz substrate and baked at 70 degrees C os very sensitive to ionizing radiation. A thin film (2.2 Mum) of this polymer/dye system is close in sensitivity to the commercially available film, which uses the same dye in another polymer at a thickness of 50 Mum. Because of the ease of application, thickness control and uniformity of the thin film, and because of the high resolution of the system, new lithographic applications for these thin films are possible. These include: 1) Measuring Exposure Tool Uniformity Exposure tool uniformity, dose variation and tool to tool

variability can e...