24 May 2004 90-nm lithography process characterization using ODP scatterometry technology
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CD-SEM and scatterometry are two of the top candidates for CD metrology in 90 nm node. In this study, Optical Digital Profilometry (ODP) based scatterometry was used to evaluate four topics: CD SEM and ODP process resolution comparison, ODP duty ratio limitation study, Poly AEI undercut sensitivity, STI ODP to TEM profile and trench depth matching. The scatterometry results were compared to CD-SEM and TEM results to develop the correlation of different metrology techniques. Scatterometry is able to provide robust uniformity measurement with additional information compared to CD-SEM. The additional information included sidewall angle, photoresist thickness, A°RC layer thickness, and under-layer film thickness. Actual data showed that this extra information was essential to trouble shoot the CD uniformity issue, separate the scanner, track, and thin film deposition impact on final CD uniformity. Scatterometry can be used not only as a metrology tool to measure CD uniformity, but also a useful analytical tool to find out the cause of CD non-uniformity. In small FEM study, scatterometry demonstrated its high resolution and precision. It can clearly identify the CD shift of less than 0.5 nm with exposure energy shift of 0.1mJ. This high resolution enabled a clearer definition of process window, and monitoring of small process shift in the actual production. From the experimental results, current optical tool with ODP technology was well qualified for duty ratio > 30 iso line measurement, detecting Poly undercut, STI profile and depth TEM matching.
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Chih-Ming Ke, Chih-Ming Ke, Shinn-Sheng Yu, Shinn-Sheng Yu, Yu-Hsi Wang, Yu-Hsi Wang, Yu-Jun Chou, Yu-Jun Chou, Jeng-Horng Chen, Jeng-Horng Chen, Bih-Huey Lee, Bih-Huey Lee, Hong-Yuan Chu, Hong-Yuan Chu, Hua-Tai Lin, Hua-Tai Lin, Tsai-Sheng Gau, Tsai-Sheng Gau, Chih-Hsiang Lin, Chih-Hsiang Lin, Yao-Ching Ku, Yao-Ching Ku, Burn Jeng Lin, Burn Jeng Lin, Jacky Huang, Jacky Huang, J. J. Hsu, J. J. Hsu, Victor Liu, Victor Liu, Dave Hetzer, Dave Hetzer, Lip Yap, Lip Yap, Wenge Yang, Wenge Yang, Kaoru Araki, Kaoru Araki, "90-nm lithography process characterization using ODP scatterometry technology", Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004); doi: 10.1117/12.536123; https://doi.org/10.1117/12.536123

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