Abstract: A material deposition process is disclosed in which apertures of a contact mask used therein have a constricted opening terminating in a `knife edge` in a sidewall thereof near the top mask side, especially within the top 25% of the mask thickness above the substrate. A process is disclosed in which the mask, in addition, has apertures which have larger dimension lower openings on a bottom side of the mask contacting the substrate than constricted openings near the top side of the mask. Single solder bump and "bump on bump" over BLM (ball limiting metallurgy) processes are disclosed which utilize such contact mask to reduce the damage and detaching of such features during processing and subsequent handling.

Abstract: A material deposition contact mask is disclosed in which apertures formed therein have a larger dimension in lower openings in a bottom side of the mask contacting the substrate than in constricted openings located near the top side of the mask. Apertures of the contact mask have knife edges located within the upper sidewalls thereof, e.g. within the top 25% of the mask thickness above the substrate. A mask is disclosed which, in addition, is thermally compensated to the substrate temperature at which the deposition is performed. Methods for fabricating the mask by differential etching are disclosed.