Defect printability of hole pattern in electron projection lithography

We investigated the defect printability of hole patterns in electron projection lithography (EPL) using a diamond reticle with a programmed defect pattern. The reticle was fabricated by NTT-AT and wafer exposure was performed using Nikon's EB projection experimental column. We simulated the defect printability to understand in greater detail. We found that the mask error enhancement factor (MEF) of the size shift defect category exceeded the value of one and was degraded by the amount of beam blur. On the other hand, the printability of the dot defect category was lower than the shift category. In particular, pin hole defects smaller than 100 nm were not printed. However the defect types of under size shift, truncation, edge intrusion, and corner intrusion (they decreased the opening area), actually increased the defect size because the defect was too small for hole patterns to print. In general, the defect printability of hole patterns depends on the beam blur, and the printed error size at the hole patterns getting larger than the line patterns. We have to pay closer attention to the hole pattern defect than to the line patterns.