Method of forming a multi-layer photo mask

Abstract

This invention provides a method of forming a multi-layer photo mask on a photo mask substrate. A first transparent layer comprising at least one vertical side wall is formed on at least one predetermined area of the photo mask substrate. A first opaque spacer is formed around the vertical side wall of the first transparent layer, and the top side of the first spacer is approximately leveled off with the upper surface of the first transparent layer. An external transparent layer is formed on the photo mask substrate and outside the predetermined area, and the upper surface of the external transparent layer is leveled off with that of the first transparent layer. So the first transparent layer and the external transparent layer form a first photo mask layer. A second transparent layer comprising at least one vertical side wall is formed on at least one predetermined area of the first photo mask layer. A second opaque spacer is formed around the vertical side wall of the second transparent layer, and the top side of the second spacer is approximately leveled off with the upper surface of the second transparent layer.

Dependencies are inferred from the claim text.