text: During the 1980s, AT&T Bell Laboratories explored the use of nitrobenzyl-based PPGs as photoresists. Over the course of the decade, they developed a deep UV positive-tone photoresist where the protected substrate was added to a copolymer of poly(methyl methacrylate) and poly(methacrylic acid). Initially, the blend was insoluble. However, upon exposure to 260 ± 20 nm light, the PPG would be removed yielding 2-nitrosobenzaldehyde and a carboxylic acid that was soluble in aqueous base.