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Copper Pillar Sidewall Wetting Prevention - Structure and Process

IP.com Disclosure Number: IPCOM000182402D
Original Publication Date: 2009-Apr-29
Included in the Prior Art Database: 2009-Apr-29
Document File: 5 page(s) / 445K

Publishing Venue

IBM

Abstract

One of the challenges of copper pillar technology is to ensure that the solder stays on top of the Cu pillar, and does not reflow to the side of the pillar (which could result in either an open or short fail). The article discloses a way to prevent this from happening it so passivate the Cu pillar sidewalls such that the solder will not wet to it.

This text was extracted from a PDF file.
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Page 1 of 5

Copper Pillar Sidewall Wetting Prevention - Structure and Process

In order to support the requirements of newer wafer technologoes, the chip-to-package interconnect structures have to be able to support:
1.) finer pitch and
2.) higher current (withstand electromigration).

One of the promising new interconnect technologies that is being developed is the relacement of a solder C4 by a copper piller. The copper piller allows higher standoff and aspect ratio, therefore enabling finer pitch. It can also support the higher currents needed for future interconnects. In addition there is a much smaller amount of solder that is used to connect the copper piller to the package.

One of the challenges of copper pillar technology is to ensure that the solder stays on top of the Cu pillar, and does not reflow to the side of the pillar (which could result in either an open or short fail). A way to prevent this from happening it so passivate the Cu pillar sidewalls such that the solder will not wet to it. Several embodiments for achieving passivation are described graphically below.

As can be seen in these images, the solder may wet to the copper sidewalls.

1

[This page contains 1 picture or other non-text object]

Page 2 of 5

The goal of this invention is to create a Cu pillar with a passivating sidewall in order to prevent the solder from wetting to the sides.

A...