23 March 2009 Sensitivity improvement and noise reduction of array CD mapping on memory device using inspection tool
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Abstract
Array CD uniformity can be measured by inspection tool and showed good correlation to traditional CD measurement such as CD-SEM and OCD.[1] Due to the inspection tool's basic requirement which collects information over whole area of wafer, the CD mapping from inspection images results in high spatial details within shot and along the wafer scale. However the reflected light which comes from the interaction between sub-wavelength array pattern and illuminated light isn't only responsible for CD variation of the illuminated area pattern. Other than lateral CD differences, thickness variation of pattern and under layer films also result in light intensity changes on reflected light. Therefore the noise separation other than CD variation is crucial factor on CD mapping using inspection tool. On the other hand, the sensitivity of CD variation is dependent on the patterned layer materials and how it interacts with the polarization of illuminated light. From previous study, reflection light from sub wavelength array structure contains CD variation information and gives linear response to the structure volume change. In this paper, CD test box which has intentional CD variation is introduced to investigate on various parameters that result in reflectivity changes. Wavelength, polarization and optical property of patterned structure are conducted to analyze the influence to the reflectivity signal. In parallel the experimental results are compared with simulation result using RCWA and good correlation is achieved.
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Jeong-Ho Yeo, Jeong-Ho Yeo, Byeong-Ok Cho, Byeong-Ok Cho, Jin-Hong Park, Jin-Hong Park, Jinseok Hur, Jinseok Hur, Seok-Hoon Woo, Seok-Hoon Woo, Seungwoon Choi, Seungwoon Choi, Chan-Hoon Park, Chan-Hoon Park, } "Sensitivity improvement and noise reduction of array CD mapping on memory device using inspection tool", Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 72721U (23 March 2009); doi: 10.1117/12.814024; https://doi.org/10.1117/12.814024
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