Method of manufacturing a bump electrode

A method of manufacturing a semiconductor device with a bump electrode of gold crystals, comprising the steps of

• providing a semiconductor substrate including a plurality of circuit elements and an insulative layer formed on the surface thereof,
• forming an electrode section on said insulative layer, wherein said electrode section is electrically connected to said circuit elements,
• forming a passivation layer on said insulative layer and on an edge portion of said electrode section, wherein the center region on the surface of said electrode section is exposed to form a concave portion,
• forming a multi-layer film covering the whole surface of the semiconductor substrate inclusive of the exposed part of the electrode section, which comprises at least a two-layer material, including a lower layer which is a material with good adhesion to said electrode section and serves as a barrier to prevent mutual diffusion between the bump electrode and the electrode section, and an upper layer which is a metal with good adhesion to said bump electrode of gold crystals,
• forming a masking material with a thickness necessary for forming a bump electrode on said multi-layer film excluding a region which is inside the concave portion wherein the area of the region of said multi-layer film that is not covered with said masking material is smaller than the center region where the edge of the photoresist layer is inside the concave portion of the electrode section, and is outside the edge of the multi-layer film over the passivation layer,
• forming a bump electrode of gold crystals with the surface of the bump electrode lower than or equal to the surface of said masking material on said electrode section by electroplating,
• thereafter removing the masking material,
• thereafter subjecting said bump electrode to a stress-reducing heat treatment, wherein an anticorrosive alloy layer is formed by the reaction of a part of the electrode section with a part of the lower layer of the multi-layer film, and
• thereafter removing by etching said multi-layer film completely from areas unoccupied by said bump electrode by using not only said bump electrode as a mask for etching said multi-layer film but also said anticorrosive alloy layer as a mask for protecting said electrode section,
• wherein said lower layer of said multi-layer film is selected from the group consisting of titanium nitride and titanium tungsten.