Improved CD-SEM optics with retarding and boosting electric fields

Ose, Yoichi; Ezumi, Makoto; Todokoro, Hideo

doi:10.1117/12.350781

Cited by 18 publications

(16 citation statements)

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“…13 We modified the model to include a focused electron beam, taking into account the spherical aberration, where the spherical aberration coefficient was calculated by an electron optics simulator using the finite-difference method. 14,15 As shown in Fig. 3, two kinds of parameters characterize the SEM waveform: sample parameters and tool parame- Pattern size is smaller than the electron scattering length.…”

Section: Modification Of Model-based Library Methodsmentioning

confidence: 99%

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 Of Model-based Library Methodsmentioning

confidence: 99%

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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“…Furthermore, local charging formed an electrostatic micro-lens and caused another problem similar to (3). (4) Optical magnification changes depending on local charging voltage, and distorts CD-measurement values.…”

Section: Wafaer Chargingmentioning

confidence: 99%

“…Local positive charging is a key technology to obtain good bottom imaging of high aspect-ratio patterns and hence it is actively built up by optimizing beam energy, electric field and irradiated area 3,4 . However, it has been noted that CD-measurement values are always larger by 1% or so than designed values on some wafer with different materials and thicknesses of insulators.…”

Section: Introductionmentioning

confidence: 99%

Correction method for high-precision CD measurements on electrostatically charged wafers

Ose¹,

Ezumi²,

Ishijima³

et al. 2002

SPIE Proceedings

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A correction method for automatic, high-precision CD-measurements on electrostatically charged wafers has been developed and installed in the Hitachi CD-SEM S-9260 to evaluate its performance. There are two types of charging: global and local. Global charging is stable and spreads all over a wafer while the local charging area is limited within the beam scanning area. A conventional CD-SEM has two weak points with respect to those charged wafers: one is failure at the positioning and autofocusing procedure which interferes with the fully automatic measurement sequence, and the other is disturbance of optical magnification which degrades the precision of CD-measurement values. By probing the global charging voltage with an electrostatic voltmeter prior to the CD-measurements, we subtract the voltage from a retarding voltage and then apply it to the wafer holder. The beam-focusing condition can stay within the fully automatically tunable range. And by generating numerical functions to represent the relationship between the global charging voltage, wafer height, excitation current of the objective lens and optical magnification, with the help of electron optical simulations, we can calculate the true optical magnification and the correct CD-measurement values. The local charging voltage is derived from the voltage shift of S-curves of secondary electron yield between conductive and insulated wafers measured with an energy filter. We correct the CD-measurement values using the simulated proportional relationship between magnifications of the electrostatic micro-lens and the local charging voltage. The coefficient is almost constant when the charging area is smaller than an equivalent circle of 100µm radius. We demonstrate that the CD-measurement values are successfully corrected within 0.1% in deviation for both charging types.

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“…2. Only the effects of spherical aberration and diffraction are considered, since spherical aberration or diffraction aberration becomes dominant in the electron probe profile, when the electron optical focusing conditions deviate from the optimum [3]. Under the optimum focusing conditions, the chromatic aberration plays significant role in the electron probe profile.…”

Section: Electron Probe Profiles For Different Defocus Valuesmentioning

confidence: 99%

“…It has been reported that this imaging method is capable of detecting 2 nm oxide remaining at the bottom of via. The electron optics and secondary electron (SE) detection system in this imaging method have been developed [3,4]. The electron optics adopts the retarding system where the primary electron beam is rapidly decelerated near the sample surface to reduce the influence of the Coulomb effect and lens aberrations, resulting in high spatial resolution even when using a high-current electron beam.…”

Section: Introductionmentioning

confidence: 99%

Estimation of electron probe profile from SEM image through wavelet multiresolution analysis for inline SEM inspection

Nakamae

Chikahisa

Fujioka

2007

Image and Vision Computing

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Improved CD-SEM optics with retarding and boosting electric fields

Cited by 18 publications

References 0 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

Correction method for high-precision CD measurements on electrostatically charged wafers

Estimation of electron probe profile from SEM image through wavelet multiresolution analysis for inline SEM inspection

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