Process latitude study of focused ion-beam-deposited gold for clear x-ray mask repair

It has been assumed that the large carbon content of FIB deposited gold films used for x-ray mask repair (as much as 50 at.%) would require that repairs be considerably thicker than the mask absorber. This paper tests this assumption by comparing the printing characteristics of FIB deposited features of varying thicknesses with those of conventional features on a mask. Ion beam deposited features 0.5 micrometers thick are found to print with nominal dose and linewidth variation most closely matching that of conventional features (0.6 micrometers electroplated Au). The results indicates that considerably less deposited material is required for repair than would be supposed based on the composition of the ion beam deposited gold (50 at.% carbon). Examples of repaired features on masks and their corresponding printed images are shown. In addition, the influence of material redeposition during clear repair is discussed.