Method and apparatus using formic acid vapor as reducing agent for copper wirebonding

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° C. and 210° 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° C. to 360° 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.

Dependencies are inferred from the claim text.