Silver-tin alloy solder bumps

• US 6,476,494 B1
• Filed: 11/11/1999
• Issued: 11/05/2002
• Est. Priority Date: 05/27/1997
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Original Assignee: Samsung Electronics Co. Ltd. (Samsung Group)
• Inventors: Park, Jong-han, Hur, Nam-jung, Kwon, Yong-hwan
• Primary Examiner(s): Wilczewski, Mary
• Application Number:
  US09/438,727
• Time in Patent Office: 1,090 Days
• Field of Search: 257/738, 257/762, 257/772, 257/778, 257/779, 257/737, 257/741
• US Class Current: 257/762
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/05001 Internal layers
• CPC Class Codes: H01L 2224/05023 the whole internal layer protruding from the surface
• CPC Class Codes: H01L 2224/0508 being stacked
• CPC Class Codes: H01L 2224/05111 Tin [Sn] as principal constituent
• CPC Class Codes: H01L 2224/05147 Copper [Cu] as principal constituent
• CPC Class Codes: H01L 2224/05155 Nickel [Ni] as principal constituent
• CPC Class Codes: H01L 2224/05568 the whole external layer protruding from the surface
• CPC Class Codes: H01L 2224/05639 Silver [Ag] as principal constituent
• CPC Class Codes: H01L 2224/1147 using a lift-off mask
• CPC Class Codes: H01L 2224/13099 Material
• CPC Class Codes: H01L 24/03 Manufacturing methods
• CPC Class Codes: H01L 24/05 of an individual bonding area
• CPC Class Codes: H01L 24/11 Manufacturing methods for bumps on insulating substrates H01L21/4853
• CPC Class Codes: H01L 24/13 of an individual bump connector
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details
• CPC Class Codes: H01L 2924/01004 Beryllium [Be]
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01022 Titanium [Ti]
• CPC Class Codes: H01L 2924/01024 Chromium [Cr]
• CPC Class Codes: H01L 2924/01029 : Copper [Cu]
• CPC Class Codes: H01L 2924/01033 : Arsenic [As]
• CPC Class Codes: H01L 2924/01047 : Silver [Ag]
• CPC Class Codes: H01L 2924/01072 : Hafnium [Hf]
• CPC Class Codes: H01L 2924/01074 : Tungsten [W]
• CPC Class Codes: H01L 2924/01078 : Platinum [Pt]
• CPC Class Codes: H01L 2924/01082 : Lead [Pb]
• CPC Class Codes: H01L 2924/014 : Solder alloys
• CPC Class Codes: H01L 2924/09701 : Low temperature co-fired ceramic [LTCC]
• CPC Class Codes: H01L 2924/14 : Integrated circuits

Abstract

Silver-tin alloy solder bumps are fabricated by forming a masked underbump metallurgy layer on a microelectronic substrate, to define exposed portions of the underbump metallurgy layer, plating silver on the exposed portions of the underbump metallurgy, plating tin on the silver and reflowing to form silver-tin alloy solder bumps. Accordingly, silver-tin alloy is not plated. Rather, individual layers of silver and tin are plated, and then reflowed to form silver-tin alloy solder bumps.

Claims

1. A solder bump structure for a microelectronic substrate, comprising:

an underbump metallurgy layer on the microelectronic substrate;

a first layer comprising silver on the underbump metallurgy layer, opposite the microelectronic substrate, wherein the first layer is between 9 μ

m and 11 μ

m thick; and

a second layer comprising tin on the first layer, opposite the underbump metallurgy layer, wherein the second layer is between 38 μ

m and 42 μ

m thick.

2. A solder bump structure according to claim 1 wherein the second layer is a mushroom-shaped second layer comprising tin.

3. A solder bump structure according to claim 1 wherein the second layer is a truncated spherical-shaped second layer comprising tin.

4. A solder bump structure according to claim 1 further comprising:

a flux coating on the first and second layers.

5. A solder bump structure according to claim 1 wherein the underbump metallurgy layer comprises:

a first underbump metallurgy layer on the microelectronic substrate, the first underbump metallurgy layer selected from the group consisting of titanium, chromium and titanium tungsten; and

a second underbump metallurgy layer on the first underbump metallurgy layer opposite the microelectronic substrate, the second underbump metallurgy layer selected from the group consisting of copper and nickel.

6. A solder bump structure according to claim 1 wherein the first layer consists essentially of silver, and wherein the second layer consists essentially of tin.

7. A solder bump structure for a microelectronic substrate, comprising:

an underbump metallurgy layer on the microelectronic substrate;

a first layer consisting essentially of silver on the underbump metallurgy layer, opposite the microelectronic substrate, wherein the first layer is between 9 μ

m and 11 μ

m thick; and

a second layer consisting essentially of tin on the first layer, opposite the underbump metallurgy layer, wherein the second layer is between 38 μ

m and 42 μ

m thick.

8. A solder bump structure according to claim 7 wherein the second layer is a mushroom-shaped second layer.

9. A solder bump structure according to claim 7 wherein the second layer is a truncated spherical-shaped second layer.

10. A solder bump structure according to claim 7 further comprising:

a flux coating on the first and the second layers.

11. A solder bump structure according to claim 7 wherein the underbump metallurgy layer comprises:

a first underbump metallurgy layer on the microelectronic substrate, the first underbump metallurgy layer selected from the group consisting of titanium, chromium and titanium tungsten; and

a second underbump metallurgy layer on the first underbump metallurgy layer opposite the microelectronic substrate, the second underbump metallurgy layer selected from the group consisting of copper and nickel.