Importance

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Abstract

A method and apparatus are disclosed for using formic acid vapor as a reducing agent during wirebonding operations to a semiconductor chip. The method and apparatus are particularly useful when wirebonding to copper metal pads. While maintaining a preferred reaction temperature between 190.degree. C. and 210.degree. C., a copper metal pad is exposed to formic acid vapor during wirebonding to remove copper oxidation from the pad to permit a good wirebond to be achieved. A less preferred reaction temperature range is 150.degree. C. to 360.degree. C. In accordance with another aspect of the invention, the concentration of formic acid vapor is controlled by mixing formic acid vapor with a gas such as nitrogen that does not participate in the reduction chemical reactions. Reaction by-products, such as carbon monoxide and hydrogen gas, may be recirculated back to further participate in the reduction chemical reactions.

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First Claim