Feedforward of mask open measurements on an integrated scatterometer to improve gate linewidth control

Sendelbach, Matthew; Natzle, W.; Archie, Charles N.; Banke, Bill; Prager, Dan; Engelhard, Dan; Ferns, Jason; Yamashita, Asao; Funk, Merritt; Higuchi, F.; Tomoyasu, M.

doi:10.1117/12.537969

Cited by 23 publications

(10 citation statements)

References 5 publications

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“…Among various methods of measuring pattern sizes, scatterometry is now widely used in LSI manufacturing. 23,24 However, it provides little information on LWR in principle because it measures only the width that is averaged over a wide area. Another method is the scanning probe microscopy that measures local LWR with an atomic-scale resolution, but its measurement range is too narrow to get the statistical information on LWR.…”

Section: Introductionmentioning

confidence: 99%

Discrete power spectrum of line width roughness

Hiraiwa

Nishida

2009

Journal of Applied Physics

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The variation of device characteristics is a challenge to present and future large-scale integrations. One of the origins of the variation is line width roughness (LWR). To facilitate the efforts to cope with LWR, we developed a method to accurately characterize LWR basing on the analysis of power spectral densities (PSDs). Because experimental PSDs are intrinsically discrete, we derive simple analytic formulas of the discrete PSDs by assuming that the autocorrelation function (ACF) exponentially decays with distance. The PSDs calculated by using the formulas agree excellently with experimentally obtained PSDs of photoresist LWR. From the result we find that the photoresist LWR of this study has a standard deviation of 2.5 nm and an exponentially-decaying autocorrelation function with a correlation length of 35 nm. Although the experimental PSDs inevitably contain a component produced by scanning-electron-microscope (SEM)-image noise, the two components of LWR and noise are separately determined by the method of this study. Due to this feature, the resultant variance of LWR is independent of the noise intensity. However, it is still important to reduce the noise component in order to maintain the accuracy of analysis especially in the case of LWR that has an unknown functional form of PSD. This is because even the PSDs that have different functional forms sometimes look alike in the presence of large noise. To reduce the noise effect, it is effective to average the SEM images perpendicularly to fine lines before edge detections. The procedure does not reduce the variance unlike averaging along the lines. The method of this study is applicable not only to LWR but also to other cases as far as the ACF exponentially decays with distance, or equivalently the spectral line shape is Lorentzian. Accordingly, it forms the basis for spectral analysis of most experimental results.

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Section: Introductionmentioning

confidence: 99%

Discrete power spectrum of line width roughness

Hiraiwa

Nishida

2009

Journal of Applied Physics

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“…In figure 2 and table II, the R 2 , slope, offset, and total measurement uncertainties (TMU) are reported. TMU is calcuated using Mandel analyis [7], which takes into account measurement uncertainties from both the tool under test (TuT) and reference tool. Here it is assumed that TMU from CD-SEM is 2.0nm.…”

Section: Ocd Methodsmentioning

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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“…These two applications were run in production with integrated scatterometry metrology, allowing advanced process control and resulting in tighter CD uniformity crossvalidated by electrical device performance [7,8]. They are well studied and provide excellent vehicles for careful characterization of the Model Optimizer methodology.…”

Section: A Structuresmentioning

confidence: 99%

Improved scatterometry time to solution for leading-edge logic applications

Vaid

Sendelbach

Komarov³

et al. 2010

2010 IEEE/SEMI Advanced Semiconductor Manufacturing Conference (ASMC)

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This paper describes an innovative approach to scatterometry modeling, significantly reducing time to solution compared to the industry's current best practices. One of the drawbacks to traditional scatterometry measurement techniques is the time required to optimize the model, which includes material optical constant extraction, model build time, initial model optimization, and model testing. A novel methodology that includes both stability and self-consistent scatterometry accuracy prediction can achieve an order of magnitude gain in productivity over prior methods. This technique creates opportunities among semiconductor chip manufacturers for wider scatterometry adoption at advanced technology nodes, where scatterometry is often the only reliable non-destructive metrology for device structure dimensions. The reductions in cycle time and improvements in accuracy prediction are keys to the success of scatterometry as an enabler for advanced process control and monitoring. This paper presents results on a conventional poly gate litho and final inspection and on leading-edge high-k metal gate after-etch applications. Spectroscopic ellipsometry is used to collect spectra from the gratings on the wafers. Then scatterometry results are obtained using the new approach and via traditional industryaccepted procedures to compare time to solution. To confirm the validity of the results, reference metrology data are collected on a CDSEM and TEM and the total measurement uncertainty is evaluated.

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Feedforward of mask open measurements on an integrated scatterometer to improve gate linewidth control

Cited by 23 publications

References 5 publications

Discrete power spectrum of line width roughness

Discrete power spectrum of line width roughness

Scatterometry performance improvement by parameter and spectrum feed-forward

Improved scatterometry time to solution for leading-edge logic applications

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