Method and apparatus for removing coating layers from alignment marks on a wafer

A method for removing coating layers from the top of alignment marks on a wafer positioned in a spin processor comprising the steps of:

• providing a spin processor equipped with a rotatable wafer chuck therein, said wafer chuck being provided with inert gas flow channels for flowing an inert gas in an upward direction;
• providing a wafer having at least one alignment mark on an active surface, said at least one alignment mark being covered with a coating layer;
• mounting an edge ring on an outer periphery of said wafer chuck, said edge ring having at least one tab section extending outwardly from an inner periphery of said edge ring toward a center of the ring, each of said at least one tab section having an area sufficiently large to overlap one of said at least one alignment mark;
• positioning said wafer with said active surface in a faced down position on said edge ring supported by said inert gas flow from said inert gas flow channels such that each one of said at least one alignment mark on said wafer overlaps and suspends over each one of said at least one tab section on said edge ring by a preset distance of not more than 5 mm;
• and
• rotating said wafer chuck and said edge ring with said wafer suspended thereon and flowing an etchant onto a backside of said wafer such that said etchant being drawn into said gap to remove said coating layer on the at least one alignment mark by capillary action.