Stabilize OMOG photomask post-repair CD variation by cleaning strategy and post-repair treatment

With wafer technology node migrating to 14nm, the noise of wafer critical dimension (CD) control from photomask become more significant due to a mask thickness no longer thin relative to the dimensions. Therefore, the Opaque MoSi-On-Glass (OMOG) photomask is widely used for high-end wafer production because its thin structure is an advantage for 3D electromagnetic field (3DEMF) mask modeling. In other words, it also means the CD control in such high-end wafer product become more and more important. The absorber layer of OMOG is composed of MoSiN which has faster etching rate. Although such kind of MoSiN can help repairing dark defect faster, it also bring some extra etchings what lead to over repair that impact photomask's CD control and yield. In order to stabilize the post-repair CD variation, we performed several treatments at pre-repair cleaning and a post-repair treatment to stabilize film properties. In addition, we also performed compositional analysis by EDX line scan to compare the compositional differences.