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Adhesion Enhancement of Thin Metal Film

IP.com Disclosure Number: IPCOM000061840D
Original Publication Date: 1986-Sep-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Appleby-Hougham, G: AUTHOR [+5]

Abstract

Adhesion of a thin metal film to a substrate can be enhanced by simply changing thickness or ductility of the film without requiring any significant change of the current process. When the substrate is coated with a polyimide layer, adhesion of the film to the layer can also be enhanced by changing the layer thickness. In order to enhance adhesion of a thin metal film to a substrate, a so-called adhesion layer is usually deposited onto the substrate before deposition of the film to increase chemical bonding. However, from an engineering point of view, such chemical bonding of the film to the substrate is not a sole factor for good adhesion of the film. This is because the film should be deformed either elastically or elasto- plastically if the film is to be lifted off.

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Adhesion Enhancement of Thin Metal Film

Adhesion of a thin metal film to a substrate can be enhanced by simply changing thickness or ductility of the film without requiring any significant change of the current process. When the substrate is coated with a polyimide layer, adhesion of the film to the layer can also be enhanced by changing the layer thickness. In order to enhance adhesion of a thin metal film to a substrate, a so- called adhesion layer is usually deposited onto the substrate before deposition of the film to increase chemical bonding. However, from an engineering point of view, such chemical bonding of the film to the substrate is not a sole factor for good adhesion of the film. This is because the film should be deformed either elastically or elasto- plastically if the film is to be lifted off. In this case, the resistance for film lift-off is a sum of the true interface adhesion strength and the strength required for deformation of the film. Therefore, the total energy (strength) which is required for lift-off film is greater if the film is thinner or if the film is more ductile. The following EXAMPLE-I demonstrates that it is possible to enhance the film adhesion by changing its thickness alone. The underlying principle as set forth above is similarly applicable to another optional case where the substrate is coated with a protective layer of polyimide. That is, by simply changing thickness of the polyimide layer, it is possible to enhance adhesion of a thin metal film to the polyimide layer without changing any of chemistries employed in the current product. This is demonstrated by EXAMPLE-II. A thin Cr layer of 500 ~ in thickness was deposited onto the flat Si substrate and then a Cu layer of different thickness was deposited. Since the interface true adhesion is achieved by the Cr chemical bonding with the Si substrate, the true adhesion strength must be the same in all the samples. The only difference is the thickness of the Cu layer. Peel tests of these samples show a great improvement of adhesion strength by reducing the thickness of...