Equipment Design Change For End Point Detection For Front Side Wafer Applications
Original Publication Date: 2001-Aug-01
Included in the Prior Art Database: 2003-Jun-19
Disclosed is a tooling method for frontside end-point detection in semiconductor and thin film wet processes, most importantly, etch and damascene plating. The idea incorporates the optical reflectance principle for monitoring an area of interest on the wafer, for a change in reflectance, indicating a change in state of the film on the wafer. There are various tool designs from a number of manufacturers for front and backside wafer processes. Many of these are for use in etch and damascene plating operations for semiconductors and thin film heads for disk drives. In addition, there are various other applications in use such as cleaning, etch, nitride/oxide etch, polymer removal, gold etch, etc. At present, the only end-point detection system in use looks at the backside of the wafer. It is an optical detector mounted on a swing arm that monitors the wafer as the arm dispenses chemical as it arcs across the wafer. If the various system designs were changed to allow for the necessary hardware to be added to incorporate optical reflectance into the tools for frontside applications, a closed loop system could be put into place allowing for absolute control of the end of the process. The reflectance system would look at the frontside of the wafer, in a particular area of interest. In the case of damascene plating and copper etch of the edge exclusion zone after plating, the detector would be aimed at the edge exclusion zone an appropriate distance in from the edge and bevel of the wafer. The distance in from the edge would be determined by the particular plating tool and the size of the wafer seal. The reflectance from the plated copper or seed area would be much higher than the reflectance from the edge of the wafer after all the copper material has been etched away. In the case of silicon wafers, the edge exclusion zone would be "black" in comparison to the copper seed/plated area. For thin film or GMR heads, the ceramic substrate or a Al2O3 layer would be exposed. In either case, there is a distinct optical difference between the layers.