Throughput simulations of the two-mask stage for high-NA EUV scanners

Since high-NA EUV scanners have a half field size, two masks are necessary for exposing a large device which is larger than the half field of 26 mm x 16.5 mm. However, it takes long time until exposing the 2nd half field since the 2nd mask would be loaded after exposing the 1st half fields on many wafers. This may cause poor characteristics at the stitching area. Recently, we have proposed a new idea which is based on a two-mask stage with a new scan method. This can drastically reduce the time until exposing the 2nd half field. Moreover, according to our scanner throughput simulation, the two-mask stage has ~1.5 times higher throughput than the single-mask stage. Although, the throughput is still ~75 % of that of a 6" x 12" mask scanner, it can be improved to ~90 %.