Printability of reticle repairs in a 248nm DUV production environment

The reduction of the CD budget is one of the key challenges of current and future semiconductor manufacturing technologies. There are many sources of CD dispersion, one of these is reticle errors, usually split into components such as linearity, uniformity across the field and mean to target offset. Reticle repairs are now emerging as another critical aspect to be added to the list of Mask Error Factors (MEF). As critical dimensions shrink down to 0.18um, 0.15um and even below, it becomes more and more difficult to build a defect free reticle right away. The frequency of reticle repairs increases with the technology complexity. It is therefore a necessity to fully characterize these defects. While repairs impact is sometimes evaluated by simulation, characterization on wafers is a lot scarcer. The purpose of this study was to link the observations made on repairs during the reticle inspection with their impact in terms of CD and process window on wafer. Reticle repairs have been characterized on various production reticles, using KLA STARlight SL300 (488nm) and AIMS (248nm) when available. The printability of these reticle repairs has then been studied on wafer. The impact on patterns close to the repair has also been measured. Patterns studied include contacts-holes and lines, on 0.18, 0.25 and 0.35um technologies. Exposure tools are ASML 248nm DUV Steppers (/300) and Step-&-Scan (/500). A CD characterization method has been defined and different repair tools have been compared.