Yoshikazu Nagamura

Novel Technique for Phase-Shifting-Mask Repair Using Focused-Ion-Beam Etch-Back Process

For the repair of phase-shifter (PS) defects with good topology and without optical deterioration, a new repair technique has been developed by using focused-ion-beam (FIB) etch-back and laser-explosion processes. This technique mainly consists of three steps: (1) leveling of defects by FIB-assisted chemical vapor deposition (CVD) or filling with spin-coated SOG film, (2) etch-back or/and exposure by Ga-FIB scanning with the detection of total secondary ions which inform the end point of etch-back, and (3) elimination of Ga-implanted shifter (or quartz) layer by a Nd:YAG laser shot. The excess shifter (bump defect) was rubbed out by adjusting the milling rate of the FIB-CVD film and its confined defects. For the missing shifter (divot defect), the filling SOG was screened off within the defect by use of Ga-FIB milling (exposure) and development. The Ga-implanted layer was eliminated by the laser explosion and so the repaired area was recovered in transmittance from less than 50% up to 98%.