Semiconductor Device and Bump Formation Process
A semiconductor device includes a solder bump overlying and electrically connected to a pad region, and a metal cap layer formed on at least a portion of the solder bump. The metal cap layer has a melting temperature greater than the melting temperature of the solder bump.
1 . A semiconductor device, comprising:
a semiconductor substrate;
a pad region on the semiconductor substrate;
a solder bump overlying and electrically connected to the pad region; and
a metal cap layer formed on at least a portion of the solder bump;
wherein the metal cap layer has a melting temperature greater than a melting temperature of the solder bump.
2 . The semiconductor device of claim 1 , wherein the metal cap layer comprises nickel.
3 . The semiconductor device of claim 1 , wherein the metal cap layer comprises palladium.
4 . The semiconductor device of claim 1 , wherein the metal cap layer comprises gold.
5 . The semiconductor device of claim 1 , wherein the metal cap layer comprises copper.
6 . The semiconductor device of claim 1 , wherein the solder bump comprises a lead-free solder material.
7 . The semiconductor device of claim 1 , wherein the metal cap layer is formed on the entire surface of the solder bump.
8 . The semiconductor device of claim 1 , wherein the metal cap layer is formed on the lower sidewall surface of the solder bump.
9 . The semiconductor device of claim 1 , wherein the metal cap layer is formed on the middle sidewall surface of the solder bump.
10 . The semiconductor device of claim 9 , wherein the solder bump comprises a bottom portion laterally spreading outside the metal cap layer.
11 . A packaging assembly, comprising:
a semiconductor substrate;
a package substrate; and
a bump structure disposed between and electrically connecting the semiconductor substrate and the package substrate;
wherein the bump structure comprises a solder bump and a metal cap layer covering at least a portion of the solder bump, and the metal cap layer has a melting temperature greater than a melting temperature of the solder bump.
12 . The packaging assembly of claim 11 , wherein the metal cap layer comprises at least one of nickel, palladium and gold.
13 . The packaging assembly of claim 11 , wherein the metal cap layer comprises copper.
14 . The packaging assembly of claim 11 , wherein the solder bump comprises a lead-free solder material.
15 . The packaging assembly of claim 11 , wherein the solder bump comprises a portion laterally spreading outside the metal cap layer.
16 . A method of forming a semiconductor device, comprising:
forming a solder material layer on a semiconductor substrate;
performing a thermally reflow process on the solder material layer; and
forming a metal cap layer on at least a portion of the solder material layer;
wherein the metal cap layer a melting temperature greater than a melting temperature of the solder material layer.
17 . The method of claim 16 , wherein the metal cap layer comprises at least one of nickel, palladium and gold.
18 . The method of claim 16 , wherein the metal cap layer is formed after the thermally reflow process.
19 . The method of claim 16 , wherein the metal cap layer is formed before the thermally reflow process.
20 . The method of claim 16 , wherein the solder material layer is a solder pillar, and the metal cap layer is formed to cover at least a portion of the sidewall surface of the solder pillar.