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Visualizing Technique for Residual Photoresist for CBS Process

IP.com Disclosure Number: IPCOM000044027D
Original Publication Date: 1984-Oct-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Jung, DY: AUTHOR [+2]

Abstract

In the peel-apart copper process residual photoresist after stripping may cause a debonding between epoxy laminates and/or an insulation resistance problem between circuit lines. Unless the residual resist forms considerably massive and thick particles, it is very difficult to be observed by an optical microscope. A visualizing technique is implemented to assess the photoresist stripability for the copper bondable surface (CBS) process. Residual resists are easily observed when a thin metallic film (about 100 - 200 ˜ in thickness) is sputter deposited on the surface. As long as the deposited film is thick enough to be opaque, it is visible even to the naked eye. The reason for the higher brightness in residual photoresist areas compared to others can be explained as follows.

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Visualizing Technique for Residual Photoresist for CBS Process

In the peel-apart copper process residual photoresist after stripping may cause a debonding between epoxy laminates and/or an insulation resistance problem between circuit lines. Unless the residual resist forms considerably massive and thick particles, it is very difficult to be observed by an optical microscope. A visualizing technique is implemented to assess the photoresist stripability for the copper bondable surface (CBS) process. Residual resists are easily observed when a thin metallic film (about 100 - 200 ~ in thickness) is sputter deposited on the surface. As long as the deposited film is thick enough to be opaque, it is visible even to the naked eye. The reason for the higher brightness in residual photoresist areas compared to others can be explained as follows. Since the "film-like" residual photoresist may be transparent (or at least semi-transparent) to the visible light, the reflected light from the rough epoxy surface will pass through the film (Fig. 1). When a thin metallic opaque film is deposited on the surface, the light can be directly reflected from the residual photoresist area. Smooth "blanket-like" residual resist material covering over the rough epoxy surface reflects more light than resist-free areas and thus appears brighter (Fig.
2).

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