METHOD FOR FORMING SOLDER BUMP IMPROVING UBM UNDERCUT

摘要

PURPOSE: A method for forming a solder bump improving UBM(Under Bump Metallurgy) undercut is provided to improve the reliability of a bump by maximizing a contact area between a UBM and a solder bump or a UBM and a buffer layer. CONSTITUTION: A UBM(38a,38b) is formed on a semiconductor chip(30) and a chip pad(32). A photoresist pattern is formed on the UBM(38a,38b). A solder bump(40) is formed on the UBM(38a,38b) exposed through the photoresist pattern. The photoresist pattern is removed. An intermetallic compound layer(44) is formed on a boundary between the solder bump(40) and the UBM(38a,38b) by heating the solder bump(40). The UBM(38a,38b) is etched by using the intermetallic compound layer(44) as a mask. A reflow process for the solder bump(40) is performed.