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The standard mask making process involves 1) resist patterning with E-beam or optical lithography and (2) pattern transfer to chrome film. The quality of the resist layers (defects, uniformity, etc.) frequently determines the quality of chrome blanks. Furthermore, the quality of resist pattern (defects, critical dimensions, etc.) frequently determines the quality of final masks. Therefore, a new technique is required which will allow manufacturers to examine the resist layer itself. Fluorescence microscopy, using either intrinsic light emission from resist material or induced emission with additives (dyes), will satisfy these demands. E-beam resists have been incorporated with fluorescence dyes and successfully exposed and patterned with standard production procedures. The enhanced contrast resulting from fluorescence techniques allows (1) easy identification of micro-flaws and contaminations, (2) accurate and precise measurement of CDs and (3) close monitoring of end-points in developing, de-scumming and stripping. Parallel experiments have also been done with optical resists. Care must be taken, though, to avoid premature sensitization of optical resists. A careful evaluation of this technique in a production environment (blank manufacturing and mask making) will be presented. Possibilities of resist image repair prior to pattern transfer will also be explored. A new class of low defect blanks will also be discussed. These blanks were produced in a highly-automated . production line, with in-line sputtering machine and hot-plate bake. Extensive evaluation at MMI over a two month period indicated that the state-of-art material can support at quality level of 0.5 DPSI (prior to repair) at 68.67. as compared to that of the standard product at 38.51%. Defect data from KLA included all pinholes, opaque spots, and perm at 1.0 - 1.5 micron level. Comparisons between plate quality of different vendors, both domestic and foreign, will also be presented.
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