Nontraditional post develop inspection and review strategy for via defects

A viable in-line monitor for missing vias in the back end of line (BEOL) has traditionally been challenging due to the nature of the defects. Today's available solutions do not meet the requirements of a true in-line and at-level monitor strategy. These solutions either indirectly monitor the defect further down the line, put production at risk of damage or contamination due to exceeding strict queue times, or inspect a very small percentage of the wafer. In this paper, we propose a new, nontraditional approach to this problem. By inspecting the wafer at post develop and reviewing at final etch, we were able to simultaneous achieve better signal to the defects and evaluate their impact to the final pattern. This methodology provides a full wafer in-line monitor strategy that was previously unavailable. The methodology was further extended to improve our lithographic process window qualification procedure and drive improvements in lithography that could not be achieved otherwise.