Impact of mask corner rounding on pitch 40 nm contact hole variability

Contact holes are traditionally designed as squares on mask but appear as circles on the wafer. The presence of the designed corners limits the center-to-center distance in certain contact hole configurations. The introduction of multi-beam mask writing enables curvilinear shapes, including contact holes with corner rounding. We investigate the imaging impact of corner rounding on pitch-40nm contact holes, exposed with an NXE:3400 EUV scanner. We observed no detectable trend of the imaging quality through corner rounding. This result indicates that the application of contact hole corner rounding will aid design optimization without imaging drawbacks specific to the corner rounding itself.