Development of the halftone phase-shift mask for DUV exposure

For bringing the halftone phase shift mask (HPSM) for 248 nm exposure into production, it is necessary to establish the mask-inspection method and mask-repair method. In this report, we will discuss the evaluation results of mask- inspection sensitivity test, comparison of mask repair methods and repaired-hole printability test. We fabricated a test mask that involves four kinds of programmed defect (clear defect; pinhole and protrusion, opaque defect; dot and intrusion), placed in 1.37 um hole array. Evaluation of defect sensitivity of KLA301 inspection system and defect printability using aerial image measurement system (AIMS) were done. Based on these results, we conclude that defect sensitivity for dot and edge defect (protrusion or intrusion) was slightly poor. We couldn't evaluate the sensitivity of pinhole. Because we could not fabricate pinholes smaller than 0.48 um and all programmed pinholes were detected. In respect of repair of clear defect, we could obtain a printability equal to holes without defects by deposition of carbon patch on the clear defect area, using a focused-ion beam (FIB). Three repairing methods of opaque defect (Laser-zapper, FIB, gas-assisted-FIB (GA-FIB)) were evaluated. Based on results of printability test using AIMS, we confirmed that GA-FIB is the best method for repairing of opaque defect. And we also report the ability of our HPSM using a chromium fluoride for ArF (193 nm) exposure.