Polymer optimization of pigmented photoresists for color filter production

The lithographic performance of pigmented photoresists for color filter production is affected by the structure of the employed polymer. Four polymers with acrylate backbones and pendant reactive acrylate/methacrvlate groups were prepared, and the effects of their molecular weights and acid values on the pixel pattern quality, development time, sensitivity and development mode were elucidated. ECHIP(TM), a statistical experimental design program was used for optimization studies revealing that the red resist performs best, when polymers with relatively low acid values (< 40 mg KOH/g polymer) and high molecular weights > 50,000 are used. The green and the blue resists yielded optimal patterns at molecular weights in the range of 20,000-30,000 with acid values of about 50-60 mg KOH/g polymer. The sensitivity of resists containing polymers with pendant acryloyl groups is in general higher than that of the corresponding methacryloyl derivatives. Polymers having butyl acrylate-methacrylic acid backbone units showed the highest sensitivity among the polymers investigated. When developed with an optimized tetramethyl ammonium hydroxide (TMAH) based developer, resists using polymers with methyl methacrylate units showed peeling type development, while butyl acrylate copolymers effected homogeneous dissolution yielding higher resolution.