New inline AFM metrology tool suited for LSI manufacturing at the 45-nm node and beyond

Edamura, Manabu; Kunitomo, Yuichi; Morimoto, Takafumi; Sekino, Satoshi; Kurenuma, Toru; Kembo, Yukio; Watanabe, Masahiro; Baba, Shuichi; Hidaka, Kumi

doi:10.1117/12.711676

Cited by 5 publications

(3 citation statements)

References 7 publications

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“…From the viewpoint of the measurement mechanism, the shape-and space-dependent measurement bias of an AFM is expected to be smaller than that of a CD-SEM especially near the middle height of a pattern. We adopted a Hitachi Kenki FineTech WA3300 AFM as the reference measurement system 13 . The WA3300 applies STEP-IN TM mode with a carbon nanotube (CNT) probe tip about 30 nm in diameter.…”

Section: Reference Measurement With Afm In Step-in Modementioning

confidence: 99%

Application of model-based library approach to Si 3 N 4 hardmask measurements

et al. 2008

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The model-based library (MBL) matching technique was applied in hardmask linewidth metrology with a criticaldimension scanning electron microscope (CD-SEM). The MBL matching measures the edge positions and shapes of samples by comparing simulated images to measured images. To achieve reliable, stable measurements, two important simulation parameters were determined empirically. One was the beam width, and the other was a material parameter, the residual energy loss rate. This parameter is especially important for measurement of hardmask patterns, which have relatively high SEM image contrast. These simulation parameters were estimated so as to fit to actual SEM images, and then pinned to the estimated values during MBL matching. Hardmask patterns made of Si 3 N 4 were measured by MBL matching with the estimated parameters. The accuracy of the measurements was evaluated by one-to-one comparison with atomic force microscope (AFM) results. The pattern profile deduced from only the top-down CD-SEM image with MBL matching agreed well with the AFM profile and a scanning transmission electron microscope (STEM) crosssectional image. The average measurement bias between the MBL matching and AFM results was 1.58 nm for the bottom CD and -0.64 nm for the top CD, with a standard deviation of about 1.3 nm.

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Section: Reference Measurement With Afm In Step-in Modementioning

confidence: 99%

Application of model-based library approach to Si 3 N 4 hardmask measurements

et al. 2008

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“…Because the probe does not oscillate up and down and touch the sample surface as in AC scanning methods, our method is free from unwanted spike noises on steep sample slopes and causes extremely little probe-tip wear. To take full advantage of these properties, we have developed an AFM sensor optimized for in-line use, which produces accurate profile data at high speeds 20,21,22,23,24,24 . The StepIn mode combined with CNT probes has been used successfully 25 .…”

Section: Introductionmentioning

confidence: 99%

AFM method for sidewall measurement through CNT probe deformation correction and its accuracy evaluation

Watanabe

Baba

Nakata

et al. 2009

Metrology, Inspection, and Process Control for Microlithography XXIII

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To use atomic force microscope (AFM) to measure dense patterns of 32-nm node structures, there is a difficulty in providing flared probes that go into narrow vertical features. Using carbon nanotube (CNT) probes is a possible alternative. However, even with its extremely high stiffness, van der Waals attractive force from steep sidewalls bends CNT probes. This probe deflection effect causes deformation (or "swelling") of the measured profile. When measuring 100-nm-high vertical sidewalls with a 24-nm-diameter and 220-nm-long CNT probe, the probe deflection can cause a bottom CD bias of 13.5 nm. This phenomenon is inevitable when using long, thin probes whichever scanning method is used. We proposed a method to deconvolve this probe deflection effect. By detecting torsional motion of the base cantilever for the CNT probe, it is possible to estimate the amount of CNT probe deflection. Using this information, we have developed a technique for deconvolving the probe deformation effect from measured profiles. This technique, in combination with deconvolution of the probe shape effect, enables vertical sidewall profile measurement.We have quantitatively evaluated the performance of the proposed method using an improved version of a "tip characterizers" developed at the National Institute of Advanced Industrial Science and Technology (AIST), which has a well-defined high-aspect-ratio line and space structure with a variety of widths ranging from 10 to 60 nm. The critical dimension (CD) values of the line features measured with the proposed AFM method showed good matches to TEMcalibrated CD values. The biases were within a range of ±1.7 nm for combinations of three different probes, five different patterns, and two different threshold heights, which is a remarkable improvement from the bias range of ±4.7 nm with the conventional probe tip shape deconvolution method. The static repeatability was 0.54 nm (3σ), compared to 1.1 nm with the conventional method. Using a 330-nm-deep tip characterizer, we also proved that a 36-nm-narrow groove could be clearly imaged.

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“…Because the probe does not oscillate up and down and touch the sample surface as in AC scanning methods, our method is free from unwanted spike noises on steep sample slopes and causes extremely little probe tip wear. To take full advantage of these properties, we have developed an AFM sensor optimized for in-line use, which produces accurate profile data at high speeds 18,19,20,21,22,22 . StepIn mode combined with CNT probes has been used successfully 22 .…”

Section: Introductionmentioning

confidence: 99%

A novel AFM method for sidewall measurement of high-aspect ratio patterns

et al. 2008

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To use atomic force microscope (AFM) to measure dense patterns of 32-nm node structures, there is a difficulty in providing flared probes that go into narrow vertical features. Using carbon nanotube (CNT) probes is a possible alternative. However, even with its extremely high stiffness, van der Waals attractive force from steep sidewalls bends CNT probes. This probe deflection effect causes deformation (or "swelling") of the measured profile. When measuring 100-nm-high vertical sidewalls with a 24-nm-diameter and 220-nm-long CNT probe, the probe deflection can cause a bottom CD bias of 13.5 nm. This phenomenon is inevitable when using long, thin probes whichever scanning method is used.We have developed a method of deconvolving this probe deflection effect that is well suited to our AFM scanning mode, AdvancedStep-in TM mode. In this scanning mode, the probe is not dragged on the sample surface but approaches the sample surface vertically at each measurement point. The CNT probe deformation is stable because we do not use cantilever oscillation that can cause instability, but we detect static flexure of the cantilever. Consequently, it is possible to estimate the amount of CNT probe deflection by detecting the degree of cantilever torsion. Using this information, we have developed a technique for deconvolving the probe deformation effect from measured profiles. This technique in combination with deconvolution of the probe shape effect makes vertical sidewall profile measurement possible.

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New inline AFM metrology tool suited for LSI manufacturing at the 45-nm node and beyond

Cited by 5 publications

References 7 publications

Application of model-based library approach to Si 3 N 4 hardmask measurements

Application of model-based library approach to Si 3 N 4 hardmask measurements

AFM method for sidewall measurement through CNT probe deformation correction and its accuracy evaluation

A novel AFM method for sidewall measurement of high-aspect ratio patterns

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