Baseline Particle Reduction of Downstream Oxide Etchers Etching Contacts and Vias

AbstractIn the process of etching contact and via openings with a downstream oxide etcher, plasma etch byproducts form polymer that collects on process chamber components. Polymer build up over time will begin to separate from chamber components and deposit on the wafer, blocking the etch and creating incomplete contact and via openings, which result in device failure. When this phenomena occurs, complete disassembling and cleaning of the chamber (wet clean) is required before particle levels are acceptable again for processing wafers. Over half of the time wet cleans are performed at or before 1500 wafers processed.Experimentation was performed to isolate one particular chamber component causing particle deposition on the wafer. Once a chamber component was isolated, possible solutions were designed so that original process parameters were not altered. The first experiment was a maintenance procedure to disassemble and clean one chamber component at set intervals between wet cleans. The second was a no wafer, high concentration Oxygen plasma chamber clean.It was found that changing a particular chamber component after 1250 wafers processed, and then again after 2500 wafers, made it possible to run to 3750 wafers before performing a wet clean. Overall particle levels were also reduced by 30% with the plasma cleans after every 100 wafers processed. The combined solutions resulted in a greater than 30% reduction in overall particle counts. Also, maintenance down time for particle failures was reduced from 57% to 19%. During the time frame of implementation of these solutions, overall factory defectivity of finished product wafers was reduced up to 25%, which relates to a 15 to 25% yield increase. The reduction of defects on the downstream oxide etcher is a contributing factor to device yield improvements.