1 June 1992 Achieving linearity for dense CD measurements with confocal metrology
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Metrology systems for submicron integrated circuit manufacturing are required to simultaneously meet stringent requirements for measurement precision, linearity, and focus- exposure tracking over a broad range of substrates and nominal structure sizes. By meeting these requirements, a system guarantees the user's ability to track changes in a lithography process. Data presented at this conference in 1991 suggested that optical metrology systems may experience resonance phenomena which adversely affect the linearity for linewidth measurements below 0.8 micrometers nominal. During the last year, however, we have been able to overcome this effect for our metrology system. The ConQuestTM 2000 white light, real time confocal metrology system was used to measure linewidths at the bottom of dense critical dimension (CD) structures from 0.35 micrometers to 1.5 micrometers nominal. Data for X and Y versus Z is acquired by scanning the sample along the optical axis of the microscope (Z direction) and acquiring an image at each Z position. The bottom of the line is found by applying a selectable focus algorithm to the data. A digitized video linescan through the measurement structure at this Z position is then analyzed and measurements of the selected edges are made. In our characterizations and evaluations, we have repeatedly seen excellent linearity results. Data is presented for a variety of substrates, including patterned photoresist and etched samples. The results reflect a high degree of precision and excellent correlation to SEM data throughout the measurement range.
© (1992) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Torsten R. Kaack, Lynda Clark Hannemann-Mantalas, Timothy R. Piwonka-Corle, "Achieving linearity for dense CD measurements with confocal metrology", Proc. SPIE 1673, Integrated Circuit Metrology, Inspection, and Process Control VI, (1 June 1992); doi: 10.1117/12.59824; https://doi.org/10.1117/12.59824

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