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

Watanabe, Masahiro; Baba, Shuichi; Nakata, Toshihiko; Morimoto, Takafumi; Sekino, Satoshi

doi:10.1117/12.772712

Cited by 23 publications

(24 citation statements)

References 29 publications

(27 reference statements)

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“…These profiles were deconvolved with the carbon-nanotube (CNT) tip shape by accounting for tip bending due to van der Waals force. 16,17 The SWAs are almost equal at ∼2 deg, although the pattern height decreases a little as the line width decreases.…”

Section: Modification 2: Fixed Tool Parametersmentioning

confidence: 95%

Accurate measurement of very small line patterns in critical dimension scanning electron microscopy using model-based library matching technique

Shishido

Tanaka

Osaki

2011

J. Micro/Nanolith. MEMS MOEMS

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Our purpose is to reduce the critical dimension (CD) bias for very small patterns with line widths of <15 nm. The model-based library (MBL) method, which estimates the dimensions and shape of a target pattern by comparing a measured scanning electron microscopy image waveform with a library of simulated waveforms, was modified in two ways. The first modification was the introduction of line-width variation into the library to overcome problems caused by significant changes in waveform due to changes in both sidewall shape and line width. The second modification was the fixation of MBL tool parameters to overcome problems caused by the reduction in pattern shape information due to merging of right and left white bands. We verified the effectiveness of the modified MBL method by applying it to actual silicon patterns with line widths in the range 10-30 nm. The CD bias measured by MBL method for three heights (20, 50, and 80%) was consistent with the atomic force microscopy results. The CD biases at all heights were <0.5 nm, and the slopes of the CD biases with respect to the CD were <3%. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

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Section: Modification 2: Fixed Tool Parametersmentioning

confidence: 95%

Accurate measurement of very small line patterns in critical dimension scanning electron microscopy using model-based library matching technique

Shishido

Tanaka

Osaki

2011

J. Micro/Nanolith. MEMS MOEMS

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“…12. According to the research, when measuring 100-nm high vertical sidewalls with a CNT probe 24 nm in diameter and 220 nm in length, the probe deflection at the bottom of the 100-nm deep trench reaches up to 6.7 nm.…”

Section: Interaction and Probe Behaviormentioning

confidence: 98%

Dimension controlled CNT probe of AFM metrology tool for 45-nm node and beyond

et al. 2008

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Atomic Force Microscope (AFM) is a powerful metrology tool for process monitoring of semiconductor manufacturing because of its non-destructive, high resolution, three-dimensional measurement ability. In order to utilize AFM for process monitoring, long-term measurement accuracy and repeatability are required even under the condition that probe is replaced. For the measurement of the semiconductor's minute structure at the 45-nm node and beyond, AFM must be equipped with a special probe tip with smaller diameter, higher aspect ratio, sufficient stiffness and durability. Carbon nanotube (CNT) has come to be used as AFM probe tip because of its cylindrical shape with small diameter, extremely high stiffness and flexibility.It is said that measured profiles by an AFM is the convolutions of sample geometry and probe tip dimension. However, in the measurement of fine high-aspect-ratio LSI samples using CNT probe tip, horizontal measurement error caused by attractive force from the steep sidewall is quite serious. Fine and long CNT tip can be easily bent by these forces even with its high stiffness. The horizontal measurement error is caused by observable cantilever torsion and unobservable tip bending. It is extremely difficult to estimate the error caused by tip bending because the stiffness of CNT tips greatly varies only by the difference of a few nanometers in diameter.Consequently, in order to obtain actual sample geometry by deconvolution, it is essential to control the dimension of CNT tips. Tip-end shape also has to be controlled for precise profile measurement.We examined the method for the measurement of CNT probe tip-diameter with high accuracy and developed the screening technique to obtain probes with symmetric tip-ends. By using well-controlled CNT probe and our original AFM scanning method called as Advanced StepIn™ mode, reproducible AFM profiles and deconvolution results were obtained.Advanced StepIn™ mode with the dimension-and shape-controlled CNT probe can be the solution for process monitoring of semiconductor manufacturing at the 45-nm node and beyond.

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“…The AFM measurement area was 2×2 µm, with 64 line scans of 1024 steps at equal sampling. The measured AFM profiles were deconvolved with a CNT tip shape accounting for the effect of tip bending due to the Van der Waals force 14 . Even with the tip deconvolution, however, there is a blind region around the bottom corner, which the tip cannot reach.…”

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

Cited by 23 publications

References 29 publications

Accurate measurement of very small line patterns in critical dimension scanning electron microscopy using model-based library matching technique

Accurate measurement of very small line patterns in critical dimension scanning electron microscopy using model-based library matching technique

Dimension controlled CNT probe of AFM metrology tool for 45-nm node and beyond

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

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