METHOD OF FORMING LEAD-FREE SOLDER ALLOYS BY ELECTROCHEMICAL DEPOSITION PROCESS

摘要

A method of forming lead-free solder bumps includes sputtering a titanium-tungsten (TiW) layer on the surface of a semiconductor wafer and a copper layer on the titanium-tungsten layer. Photoresist is used to define a contact area on the copper layer. A layer of solderable electrically conductive material is plated on the sputtered copper layer in the contact area, a layer of silver is plated on the solderable material, and a layer including tin is plated on the silver. The photoresist material is removed and, using the tin, silver, and solderable material layers as a mask, the sputtered copper and the titanium-tungsten are etched away from the surface of the wafer surrounding the contact area. The tin, silver, and solderable material layers are then reflowed to form a solder alloy bump.