Proposals of a two-mask stage scanner for high-numerical-aperture extreme ultraviolet lithography

As high-numerical-aperture (NA) extreme ultraviolet (EUV) scanners have a half-field size, two masks are necessary for exposing a chip that is larger than the half-field of 26 mm×16.5 mm. However, scanner throughput simulations have cleared that it takes a long time to expose the second half-field because the second mask should be loaded on the mask stage after exposing the first half-fields on many wafers to improve the throughput. Consequently, this may affect the stitching area due to a long waiting time after the first half-field exposure until the post-process. Therefore, an introduction of a two-mask stage scanner is proposed. This can drastically reduce the time until exposing the second half-field. However, using a conventional scan with two masks on a single mask stage, the two exposed areas are separate. Therefore, a new scan method is proposed, in which the two exposed areas contact. The scanner throughput simulations indicate that the scanner with the two-mask stage has a 20% to 80% higher throughput than the conventional single-mask scanner. The throughput can be even ∼85% of that of a scanner with a 6 in.×12 in. mask.