For the latest photomask fabrication, critical dimension (CD) control is required more for ArF lithography. To satisfy the requirement, Alternating Phase-Shifting Mask (Alt.PSM) is expected to be the most effective approach for resolution enhancement. We investigated the optimization of shifter structure and evaluated phase defect detectability for 130 to 100nm node ArF Alt.PSM. Considering the process and defect control, shifter trench type is the most popular approach. However, in order to achieve smaller CD on reticle, dual trench type becomes also necessary. Therefore, we investigated the performance of the two types of shifter structure, and we compared the optical characteristics. On the other hand, Using test reticles contained programmed phase defects of various shape and size, phase defect printability was analyzed with the Aerial Image Measurement System, MSM193, and phase defect detectability was evaluated with some inspection tools. As a result, the manufacturing technology of ArF Alt.PSM for 100nm node was established.