Glass photomasks having a stained pattern within the glass for use in photolithographic processes are made by exposing and developing a photoresist on a sheet of glass and subsequently migrating stain-producing ions, such as silver and/or copper, into the surface of the glass under the influence of an...http://www.google.com.au/patents/US4155735?utm_source=gb-gplus-sharePatent US4155735 - Electromigration method for making stained glass photomasks
