Removal Method of Nano-Cut Debris for Photomask Repair Using an Atomic Force Microscopy System

Recently, photomask repairing techniques by scratching fabrication using an atomic force microscopy (AFM) system have been developed. However, the machining method using AFM produces cut debris during photomask repair, which induces problems and errors in photolithography. Here, we describe a novel removal method for cut debris produced in an AFM photomask repair process. The removing method is based on electrophoretic migration. A small amount of aqueous solution is dropped on a cantilever, then two electrodes placed on both sides of the cantilever form an electric field gradient around the cantilever under the liquid condition. Under the condition, the particles of cut debris produced by AFM scratching are dispersed and become spontaneously charged in the liquid, and then the particles can be consequently removed by electrophoresis migration. In particular, smaller cut particles produced by ultrasonic scratching, that is, scratching with probe oscillation, are very suitable for the removal method owing to the ease of electrophoresis migration. These techniques would be very effective in the AFM photomask repair process.