Repair Technology for Large Scale Photomasks

Repair technologies by using focused ion beam (FIB) and laser have been applied to large scale photomasks for plat panel displays (FPD). In recent years, repair accuracy requirement for FPD masks has been higher than before. In this study, we investigated the repair accuracy improvement by modifying imaging conditions and process scanning. As improvement of imaging conditions, beam diameter was shrunken to be about half of the original. Pixel pitch of imaging was shrunken to be 4 times as small as the original. As improvement of process scanning, scanning method was changed from raster type to vector type. Actual repair accuracy was evaluated by measuring repair edge positions on scanning ion microscopy (SIM) images after etching or deposition. The original repair accuracies were 238 nm and 150 nm @ 3sigma, but those in the most improved cases were only 23 nm and 20 nm @ 3sigma which is 10 times as small as the originals. Those results demonstrate that the above modification can significantly improve repair accuracy.