METHOD FOR ETCHING GOLD IN AN MRIE
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2002-May-08
A standard under bump metallurgy (UBM) used in the electroplated gold bump process is TiW/Au. Wet chemistry etches including KII,, KCN or Thio- urea based etch solutions have long been used to remove the Au film. Hot H,O, is then used to remove the TiW layer. Both processes suffer from the typical problems associated with wet etches. Sta- bility of bath chemistry, uniformity of etch as well as chemical usage and waste are some of the issues. With the increasing demand for higher I/OS and smaller die, undercut of the UBM becomes signifi- cant on the smaller fine pitch bumps.