Simultaneous overlay and CD measurement for double patterning: scatterometry and RCWA approach

Li, Jie; Liu, Zhuan; Rabello, Silvio; Dasari, Prasad; Kritsun, Oleg; Volkman, Catherine; Park, Jungchul; Singh, Lovejeet

doi:10.1117/12.814706

Cited by 9 publications

(9 citation statements)

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“…At normal incidence, reflectance spectra are collected by aligning the electric field parallel (referred as TE mode) or perpendicular (referred as TM mode) to the periodic structure. The details of hardware configuration can be found in the reference [3].…”

Section: Optical Systemmentioning

confidence: 99%

Scatterometry performance improvement by parameter and spectrum feed-forward

Li¹,

Zangooie

Boinapally³

et al. 2014

Metrology, Inspection, and Process Control for Microlithography XXVIII

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Optical critical dimension (OCD) metrology using scatterometry has been widely adopted for fast and non-destructive in-line process control and yield improvement. Recently there has been increased interest in metrology performance enhancement through a holistic approach. We investigate the benefits of feed-forward of metrology information from prior process steps using samples from magnetic hard disk drive manufacturing. The scatterometry targets are composed of rather isolated gratings that are designed to have better correlation with device features. Two gratings, one with pitch ≈ 10CD, and the other with pitch ≈ 15CD, are measured at post develop and post reactive ion etch (RIE) steps. Two methods: parameter feed-forward (PFF) and spectrum feedforward (SFF) are studied in which the measurement results or spectrum collected on the blanket target at photo step are fed forward to the measurements on the grating structures at post develop or post RIE step. Compared with standard measurement without FF, for the more isolated grating at photo step, both PFF and SFF improve CD correlation from R 2 =0.96 to R 2 =0.975 using CD-SEM results measured on device as the reference. Dynamic precision and fleet measurement precision are improved by 20-60%. For post RIE step, PFF and SFF significantly improve CD correlation from R 2 =0.95, slope=1.09 to R 2 =0.975, slope=1.03 for the denser grating, and from R 2 =0.90, slope=0.79 to R 2 =0.96, slope=0.96 for the more isolated grating. Dynamic precision is generally improved by 20-40%. It is observed that both PFF and SFF are equally efficient in reducing parameter correlation for the application studied here.

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Section: Optical Systemmentioning

confidence: 99%

Scatterometry performance improvement by parameter and spectrum feed-forward

Li¹,

Zangooie

Boinapally³

et al. 2014

Metrology, Inspection, and Process Control for Microlithography XXVIII

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“…Previously DBO data of high accuracy and high precision were reported for double patterning process using normal incidence spectroscopic reflectometry (NISR) [1][2][3]. In this work we evaluate DBO performance using two test wafers from dynamic randomaccess memory (DRAM) manufacturing process.…”

Section: Introductionmentioning

confidence: 98%

“…It offers convenience of quick recipe setup since there is no need to establish a model. Recent advances in modeling capability and computation power enabled mDBO [1], which allows measurements with less number of pads per target, reducing the total target size and measurement time. In this work we evaluate eDBO performance using five DBO targets designed with different pitches and programmed shifts.…”

Section: Introductionmentioning

confidence: 99%

Evaluating diffraction-based overlay

Li¹,

Tan²,

Jung³

et al. 2012

SPIE Proceedings

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We evaluate diffraction-based overlay (DBO) metrology using two test wafers. The test wafers have different film stacks designed to test the quality of DBO data under a range of film conditions. We present DBO results using traditional empirical approach (eDBO). eDBO relies on linear response of the reflectance with respect to the overlay displacement within a small range. It requires specially designed targets that consist of multiple pads with programmed shifts. It offers convenience of quick recipe setup since there is no need to establish a model. We measure five DBO targets designed with different pitches and programmed shifts. The correlations of five eDBO targets and the correlation of eDBO to image-based overlay are excellent. The targets of 800nm and 600nm pitches have better dynamic precision than targets of 400nm pitch, which agrees with simulated results on signal/noise ratio. 3σ of less than 0.1nm is achieved for both wafers using the best configured targets. We further investigate the linearity assumption of eDBO algorithm. Simulation results indicate that as the pitch of DBO targets gets smaller, the nonlinearity error, i.e., the error in the overlay measurement results caused by deviation from ideal linear response, becomes bigger. We propose a nonlinearity correction (NLC) by including higher order terms in the optical response. The new algorithm with NLC improves measurement consistency for DBO targets of same pitch but different programmed shift, due to improved accuracy. The results from targets with different pitches, however, are improved marginally, indicating the presence of other error sources.

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“…Traditional technologies such as image-forming optical-or electron-beam-based CD and OL metrologies are gradually replaced by faster and more sensitive diffraction-based metrology. Both, single wavelength angle-resolved and broadband spectroscopic scatterometry have been gaining in importance for the control of lithography focus and dose variation and pattern placement [1,2] as well as for etch parameter control. At a typical collection rate of 3000 data points per hour, scatterometric CD and OL metrology is two to three times faster than comparable image-forming methods.…”

Section: Introductionmentioning

confidence: 99%

Full wafer macro-CD imaging for excursion control of fast patterning processes

Markwort¹,

Kappel²,

Kharrazian³

et al. 2010

SPIE Proceedings

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A powerful new inspection technology enables the excursion control of fast patterning processes. Full images of 300mm wafers are captured and processed to extract CD uniformity information of contact hole and line-space patterns. Suitable masking filters are applied to process and analyze the information from active logic and/or memory areas separately. Characteristic process tool signatures can then be detected based on die, exposure field and wafer-level pattern variations. Based on inspection times of a few seconds per wafer, rapid monitoring of 100% of processed wafers at full surface is feasible. CD-imaging is demonstrated for the monitoring of key patterning process steps in gate formation. Use cases for stand-alone, integrated and smart sampling strategies are discussed.

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Simultaneous overlay and CD measurement for double patterning: scatterometry and RCWA approach

Cited by 9 publications

References 0 publications

Scatterometry performance improvement by parameter and spectrum feed-forward

Scatterometry performance improvement by parameter and spectrum feed-forward

Evaluating diffraction-based overlay

Full wafer macro-CD imaging for excursion control of fast patterning processes

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