The sensitivity of localized photochemical etching to the optical and electrical properties of multilayered semiconductor materials is utilized for selectively etching a laterally extending undercut in a buried layer. The semiconductor body is immersed in a suitable etching solution and a beam of light...http://www.google.com/patents/US5081002?utm_source=gb-gplus-sharePatent US5081002 - Method of localized photohemical etching of multilayered semiconductor body
