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FORMATION OF Cu-Au INTERDIFFUSION BARRIER BY C+ IMPLANTATION

IP.com Disclosure Number: IPCOM000036660D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Chang, CA: AUTHOR [+2]

Abstract

The Cu-Au thin film structure is widely used in contact metallurgy, with Cu providing conduction and Au for the protection of Cu against environmental corrosion and oxidation. However, even at relatively low temperatures, 200-300oC, severe interdiffusion of Cu and Au takes place. This changes the electrical and the metallurgical properties of each metal so that Au no longer provides any protection for Cu. In packaging technology, where Au also provides good bonding properties for joints, Cu diffusion into Au reduces the rework capability of the Au. Ni or Co layers are commonly used to control interdiffusion of Cu-Au, but Cu diffuses through these layers into Au irrespective of their thickness 1.

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FORMATION OF Cu-Au INTERDIFFUSION BARRIER BY C+ IMPLANTATION

The Cu-Au thin film structure is widely used in contact metallurgy, with Cu providing conduction and Au for the protection of Cu against environmental corrosion and oxidation. However, even at relatively low temperatures, 200- 300oC, severe interdiffusion of Cu and Au takes place. This changes the electrical and the metallurgical properties of each metal so that Au no longer provides any protection for Cu. In packaging technology, where Au also provides good bonding properties for joints, Cu diffusion into Au reduces the rework capability of the Au. Ni or Co layers are commonly used to control interdiffusion of Cu-Au, but Cu diffuses through these layers into Au irrespective of their thickness 1.

In this disclosure, it is demonstrated that a Cu-Au interdiffusion barrier can be produced by the implantation of a low energy/ medium dose of suitable ion species. An example is C+ ions implanted into Cu before Au deposition at an energy of 40 keV and a dose of 1-2x1017 ions/cm2 . This results in a very significant reduction in Cu diffusion into Au at 400oC. Copper generally diffuses along grain boundaries 2. The reduction in Cu diffusion due to C+ implantation must be due to C segregation along the grain boundaries. Other ion species that will behave similarly to C, or that will form intermetallic compounds within the implanted region, thereby acting as diffusion barriers, should also be effective. Ion implan...