Plasma etching process for refractory metal vias

摘要

An etchback process for etching a refractory metal layer formed on a semiconductor substrate with a greatly reduced micro-loading effect. The etch proceeds in three steps. The first step is a uniform etch which utilizes a gas chemistry of SF6, O2 and He and proceeds for a predetermined time to remove most of the metal layer. The second step is a very uniform etch which utilizes a gas chemistry of SF6, Cl2 and He and proceeds until the endpoint is detected. The endpoint is detected by measurement and integration of the 772 nm and 775 nm lines of Cl. The third step is a timed etch utilizing a gas chemistry of Cl2 and He which is used as both an overetch to ensure complete removal of the refractory metal film and as a selective etchant to remove an adhesion underlayer.