Feasibility study of mask fabrication in double exposure technology

With decreasing the design node, there are some candidates for the optical lithography technology. Double Exposure Technology (DET) is the one of the solution to extend the resolution limit down to k1 less than 0.25 for the next generation devices. To accomplish DET, photomask MTT, CD uniformity, and the overlay between the layers for the dual exposure are important as the photomask process aspect. MTT and CD uniformity have been frequently discussed for Single Exposure Technology (SET), but the overlay and the registration have not been discussed yet with the view of DET. In this work, the feasibility of mask fabrication, especially the overlay and the registration for DET are analyzed. The current mask limit of DET is discussed considering MTT, uniformity, and overlay.