REDUCTION OF VARIATION IN REFLECTIVITY OF A1 AND AlSi TOP METAL ON SEMICONDUCTOR DEVICES
Original Publication Date: 1996-Aug-01
Included in the Prior Art Database: 2002-Apr-25
Wafers having non-uniform bond pad reflectivity have caused poor pattern recognition during the wire bond qperation at assembly. The top metal used on discrete semiconductor devices (transistors, Diodes, MOS) is Al or AlSi. Where this top metal is directly over boron doped contact areas, its reflectivity has unpredictable, non-uniform variation. In order to improve non-uniform metal reflectivity in boron doped contact areas, a mild silicon etch is used to remove a thin boron doped film prior to top metal disposition. The thin boron doped film imparts a smooth, shiny appearance to the top metal. Elevated top metal deposition temperature also plays a role in producing uniform metal reflectivity across the semiconductor wafer.