A Comparative Risk Assessment of Casting Solvents for Positive Photoresist

Abstract A practical methodology for conducting a comparative risk assessment is applied to the problem of identifying a less toxic casting solvent(s) for positive photoresist. Conventional solvents used in photoresists are ethylene glycol-derived ethers, principally 2-ethoxyethyl acetate, commonly known as CEIXOSOLVE® Acetate.A Concern has grown in recent years over possible reproductive risks of 2-ethoxyethyl acetate and structurally related glycol ethers. Animal toxicology studies indicate that these solvents may induce teratogenic and fetotoxic effects as well as male reproductive effects in animals exposed to air concentrations ranging from 3 ppm to 100 ppm. Three general concepts in glycol ether toxicology have emerged from the animal data: 1. Toxicological equivalence, mole for mole, of a glycol ether and its acetate. 2. Inverse relationship between reproductive toxicity and length of the substituted alkyl group. 3. Biologic activation of ethylene glycol ethers to an alkoxy-acetic acid metabolite (...