11 March 2002 Utilization of optical emission endpoint in photomask dry etch processing
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Abstract
Use of accurate and repeatable endpoint detection during dry etch processing of photomask is very important for obtaining good mask mean-to-target and CD uniformity performance. It was found that the typical laser reflectivity endpoint detecting system used on photomask dry etch systems had several key limitations that caused unnecessary scrap and non-optimum image size performance. Consequently, work to develop and implement use of a more robust optical emission endpoint detection system for chrome dry etch processing of photomask was performed. Initial feasibility studies showed that the emission technique was sensitive enough to monitor pattern loadings on contact and via level masks down to 3 percent pattern coverage. Additional work was performed to further improve this to 1 percent pattern coverage by optimizing the endpoint detection parameters. Comparison studies of mask mean-to-target performance and CD uniformity were performed with the use of optical emission endpoint versus laser endpoint for masks built using TOK IP3600 and ZEP 7000 resist systems. It was found that an improvement in mean-to-target performance and CD uniformity was realized on several types of production masks. In addition, part-to-part endpoint time repeatability was found to be significantly improved with the use of optical emission endpoint.
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Thomas B. Faure, Cuc Huynh, Michael J. Lercel, Adam Smith, Thomas Wagner, "Utilization of optical emission endpoint in photomask dry etch processing", Proc. SPIE 4562, 21st Annual BACUS Symposium on Photomask Technology, (11 March 2002); doi: 10.1117/12.458343; https://doi.org/10.1117/12.458343
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