Method for forming solder bumps using sacrificial layer
First Claim
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1. A circuit comprising:
- a plurality of spaced apart electrically conductive contact pads located directly on a surface of a substrate;
a solder resist layer located between each electrically conductive contact pad and located directly on the substrate, wherein a portion of the solder resist layer is disposed onto a topmost surface of each electrically conductive pad;
a solder bump disposed on a physically exposed surface of each electrically conductive pad and partially disposed on a topmost surface of each solder resist layer, wherein the solder bump comprises tin that is alloyed with at least a first metal selected from a rare earth metal, wherein the rare earth metal is non-homogeneously dispersed throughout the solder bump; and
a metallic layer composed of at least the first metal located between the solder bump and each electrically conductive pad.
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Abstract
A barrier layer is formed over electrically conductive contact pads on a substrate such as a wafer. A photoresist layer is applied over the barrier layer, and openings in the photoresist layer are filled with solder to form solder bumps. The barrier layer may be removed from within the openings prior to filling the openings with solder. The process is applicable to fine pitch architectures and chip size packaging substrates. The photoresist layer and portions of the barrier layer outside of the openings are removed following solder fill.
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Citations
17 Claims
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1. A circuit comprising:
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a plurality of spaced apart electrically conductive contact pads located directly on a surface of a substrate; a solder resist layer located between each electrically conductive contact pad and located directly on the substrate, wherein a portion of the solder resist layer is disposed onto a topmost surface of each electrically conductive pad; a solder bump disposed on a physically exposed surface of each electrically conductive pad and partially disposed on a topmost surface of each solder resist layer, wherein the solder bump comprises tin that is alloyed with at least a first metal selected from a rare earth metal, wherein the rare earth metal is non-homogeneously dispersed throughout the solder bump; and a metallic layer composed of at least the first metal located between the solder bump and each electrically conductive pad. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A circuit comprising:
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a plurality of spaced apart electrically conductive contact pads located directly on a surface of a substrate; a solder resist layer located between each electrically conductive contact pad and located directly on the substrate, wherein a portion of the solder resist layer is disposed onto a topmost surface of each electrically conductive pad; and a solder bump disposed on a physically exposed surface of each electrically conductive pad and partially disposed on a topmost surface of each solder resist layer, wherein the solder bump comprises an alloy of tin and a rare earth metal, wherein the rare earth metal is non-homogeneously dispersed throughout the solder bump. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification