MIM Surface Reconditioning Under Knudsen Flow During Metal Deposition Process

Failure analysis revealed that capacitor short-circuit failures were related to a MIM metal missing/peeling defect. During subsequent investigation a correlation between MIM top metal defects and Knudsen flow conditions within the metal deposition system was revealed. MIM surface condition prior to and after top metal deposition was extensively studied. MIM surface characterization showed large size particles formed on the MIM feature after the wafer experienced Knudsen flow. Experiments show such defects could also be produced after multiple oxygen plasma cleans and long staging time of exposed MIM features. These same changes of the MIM surface condition occurred at an accelerated rate under Knudsen flow conditions in the metal deposition system. Inline AOI results showed that when the Knudsen number was at or greater than ~0.2 during vacuum load lock pumping, MIM metal missing/peeling defects were formed, affecting up to 20% of die.