PSM defect repair using currently available tools

Phase shifting masks (PSMs) have proven to increase resolution in optical lithography. However, the production of defect free PSMs still remains a challenge. The increase in resolution not only decreases the maximum allowed chromium defect size, but also introduces phase defects which print at even smaller sizes than conventional defects. This paper will describe typical defects on quartz etched Rim shifting and Attenuated PSMs as well as the minimum requirements for repairing these defects during the process development phase. Finally, possible PSM repair methods using conventional mask repair techniques such as focused ion beam sputtering and laser ablation will be discussed.