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8 December 1995 Embedded attenuating phase-shift mask: printability of defects
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Abstract
The manufacture of an embedded attenuating phase shift mask (E-APSM) is the simplest among all the phase shift mask (PSM) types. This is because an E-APSM provides the necessary attenuation and phase shift requirements using a single layer absorber film. Therefore, the tasks of patterning, inspection and repair are much easier to accomplish than for a multi-level quartz etched or SOG/SiO2 coated PSM. Reports in literature indicate that an E-APSM, also referred to as a single-layer half-tone PSM, is likely to be used for the contact masking layer in the manufacture of 64 M-bit DRAMs. It has also been stated that defect-free E-APSMs will be manufactured using currently available mask making tools. Therefore, it could be inferred that the defect specifications for an E-APSM are expected to be the same as that for a standard chrome mask. Perturbation modeling studies indicate that this should be true. An experimental study of repair and printability of defects on contacts on an E- APSM, using a chrome-based embedded attenuating film was performed. Exposures were made on an i-line stepper with NA equals 0.6 and sigma equals 0.6. Oxide wafers were coated with a high contrast i-line resist and the contact pattern was transferred into the oxide using a decorative etch process. Measurements were made using a SEM. The wafer results were also compared with printability studies done using an aerial imaging measurement system. The results of repairs done on 1 micrometer size defects on 2 micrometer size contacts indicate that the currently available laser repair tool was successful in restoring the lithographic performance of the E-APSM contacts to an acceptable level.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Rajeev R. Singh, Alvina M. Williams, Chi-Min Yuan, Greg P. Hughes, G. Foss, and Ronald M. Martino "Embedded attenuating phase-shift mask: printability of defects", Proc. SPIE 2621, 15th Annual BACUS Symposium on Photomask Technology and Management, (8 December 1995); https://doi.org/10.1117/12.228181
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