Measurement correlation and tool matching of multiple CD-SEMs

Justin J. Hwu; Sukhbir S. Dulay; Thao Pham

doi:10.1117/12.483757

2 June 2003 Measurement correlation and tool matching of multiple CD-SEMs

Justin J. Hwu, Sukhbir S. Dulay, Thao Pham

Proceedings Volume 5038, Metrology, Inspection, and Process Control for Microlithography XVII; (2003) https://doi.org/10.1117/12.483757
Event: Microlithography 2003, 2003, Santa Clara, California, United States

Abstract

A methodology is proposed to evaluate measurement correlation and matching feasibility between CDSEMs from different vendors in a multiple tool environment. Two CDSEMs from different vendors are used in this study. The measurement correlation and matching feasibility is identified through a series of steps. The pixel oversampling of both CDSEMs were first adjusted to the same extent in order to achieve the same scan pixel signal-to-noise ratio on both CDSEMs. Then the corresponding linescan smoothing and averaging were lowered but optimized with the precision criterion of less than 2 nm. The scan pixel magnification calibrations on both CDSEMs were traced back to an internal pitch standard. The corresponding measurement linearity was checked against a resolution mask from which wafers with pitch ranging from 400 to 800 nm were generated using a 248 nm stepper. The resulting scanning magnification correction factors for both CDSEMs in two scan orientations were determined for the follow-on measurement corrections on 248 nm resist focus exposure pattern (FEM) wafers and e-beam resist wafers obtained from e-beam lithography. The algorithms' characteristics between two CDSEMs were identified and they were adjusted to use only the information derived from the first linescan derivative in order to maintain maximum algorithm similiarity. The 120 nm process window on 248 nm resist wafers has a positive 1.6 nm offset from CDSEM A to B through focus. Both CDSEMs report the same process latitude for 110 nm process window identification. The measurement correlation study on e-beam resist shows offsets of negative 1.5 and 2 nm from CDSEM A to B, depending on which CDSEM is used first for the measurement sequence. Analysis-of-variance was used to analyze the measurement correlation. It is found that there is no significant difference in offsets generated regardless of which CDSEM is used first for performing the measurement for the 248 nm resist system. However, the offset generated for e-beam resist is dependent on measurement sequence. We conclude that CDSEMs from different vendors can be adjusted to maintain a constant offset over a CD variation range since after tuning all the factors mentioned both CDSEMs have very similar responses toward resist line secondary characteristics. Therefore these two CDSEMs are viewed as matched from a process development and process control prospective. All other CDSEMs in the same vendor group are then matched to each of the two bridged CDSEMs following the correposponding vendor's routine without any major procedure change.

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Justin J. Hwu, Sukhbir S. Dulay, and Thao Pham "Measurement correlation and tool matching of multiple CD-SEMs", Proc. SPIE 5038, Metrology, Inspection, and Process Control for Microlithography XVII, (2 June 2003); https://doi.org/10.1117/12.483757

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KEYWORDS

Semiconducting wafers

Line scan image sensors

Smoothing

Critical dimension metrology

Deep ultraviolet

Algorithm development

Calibration

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