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Browse Prior Art Database

Laser Ablative Cleaning of Bonding Surfaces

IP.com Disclosure Number: IPCOM000036237D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 68K

Publishing Venue

IBM

Related People

Arjavalingam, G: AUTHOR [+4]

Abstract

Disclosed is a technique to remove organic and/or inorganic residues from the surfaces of wire bonding or solder attach pads employed in microelectronic packaging applications. The method involves using a laser pulse of appropriate wavelength and fluence to ablate the contaminants and render the pad surface more amenable for bonding operations.

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Laser Ablative Cleaning of Bonding Surfaces

Disclosed is a technique to remove organic and/or inorganic residues from the surfaces of wire bonding or solder attach pads employed in microelectronic packaging applications. The method involves using a laser pulse of appropriate wavelength and fluence to ablate the contaminants and render the pad surface more amenable for bonding operations.

Microelectronic components are typically exposed to elevated temperatures and/or process steps during fabrication. These exposures result in a thin metal oxide overlayer or an organic film on the surface of bonding pads, which typically comprise CuAu or CuNiAu metallizations (see Fig. 1A for a typical Auger surface analysis survey). Difficulties in solder wetting and wire bonding are often experienced in this situation since the bonding or wetting forces cannot break down or undercut these contaminant layers.

It is possible to remove such contaminants using laser ablation. For example, using a Q-switched Nd/YAG laser one can selectively remove these layers without significantly altering the underlying metallization. Fig. 1B is the Auger survey of the same area as in Fig. 1A, but after a laser ablative cleaning step. The cleaning operation can be carried out in laser microbes that are commercially available and are capable of delivering controlled amounts of laser fluence to effect the removal of layers as thin as a few hundred angstroms [*]. Removal of differing types of surface...