IMPROVING X-RAY MASK PATTERN PLACEMENT ACCURACY BY CORRECTING PROCESSDISTORTION IN ELECTRON-BEAM WRITING

A new correction method named PAT (previous analysis of distortion and transformation of coordinates) has been developed for improving the p attern placement accuracy of completed X-ray masks. PAT compensates fo r total-process distortion in tile electron beam writing step. In PAT, overall pattern position shifts are estimated using a send-ahead mask in advance of making working masks. Then the pattern position shifts obtained from the send-ahead mask are compensated for during electron beam writing. In all experiment, the pattern placement error of a comp leted X-ray mask represented by 3 sigma was reduced tu below 0.07 mu m . This confirmed that highly accurate X-ray masks could be fabricated using PAT.