Reticle error correction for lithography tool qualification benefits and limitations

2001 
The objective of the Reticle Error Correction (REC) is to determine the exposure tool fingerprint in the Across Chip Linewidth Variation (ACLV). Extensive reticle and wafer measurements indicate hidden reticle issues contributing to ACLV. Some of these obscure reticle issues originate from the way the mask is produced, e.g. due to mask processing and mask writer equipment. Mask processing is traditionally focused upon as the largest cause for ACLV, but on high quality masks, mask writer properties can appear. In order to take these additional properties into account, an extended REC model is required using information from the nearest neighbors. If not all the required reticle properties are measured and used, either by choice or by tool inability, then a reticle fingerprint also (partially) dominates the exposure tool fingerprint. The quality of the reticle measurements determines how well the exposure tool fingerprint can be revealed. REC is used to separate reticle and exposure tool contributions from ACLV. The methods that are used, and the results that are obtained, serve as a guide in showing where improvements can be made in mask making, mask metrology and exposure tools.
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