Optical through-focus technique that differentiates small changes in line width, line height, and sidewall angle for CD, overlay, and defect metrology applications

Attota, Ravikiran; Silver, Richard M.; Barnes, Brian M.

doi:10.1117/12.777205

Cited by 21 publications

(19 citation statements)

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“…The polarization state of the illumination produces different sensitivities for a given dimensional difference. This is illustrated in Reference [8] for an isolated line at λ = 193 nm and 100 nm nominal line height and linewidth for unpolarized, TE-polarized (electric field pointing along the lines), and TM-polarized (electric field pointing perpendicular to the lines) illumination. The results show a large difference in the MSD values (i.e., sensitivity) depending on the illumination polarization for a 2.0 nm difference in the line height.…”

Section: Optimizationmentioning

confidence: 98%

“…Under the given simulation conditions, the TM polarization produced the maximum sensitivity, about 10 times the sensitivity of unpolarized light. Similarly one can optimize the experimental conditions, such as illumination numerical aperture or collection numerical aperture, to produce a maximum sensitivity [8].…”

Section: Optimizationmentioning

confidence: 99%

“…This information can be obtained using an appropriate data acquisition and analysis method. Based on this and on the observation of a distinct signature for different parametric variations, we introduced a new method for nanoscale dimensional analysis with nanometer sensitivity for three-dimensional, nano-sized targets using a conventional brightfield optical microscope [7][8][9][10][11][12][13][14]: through-focus scanning optical microscopy (TSOM). TSOM is applicable to threedimensional targets (where a single "best focus" may be impossible to define), thus enabling it to be used for a wide range of target geometries and application areas.…”

Section: Introductionmentioning

confidence: 99%

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TSOM method for semiconductor metrology

et al. 2011

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Through-focus scanning optical microscopy (TSOM) is a new metrology method that achieves 3D nanoscale measurement sensitivity using conventional optical microscopes; measurement sensitivities are comparable to what is typical when using scatterometry, scanning electron microscopy (SEM), and atomic force microscopy (AFM). TSOM can be used in both reflection and transmission modes and is applicable to a variety of target materials and shapes. Nanometrology applications that have been demonstrated by experiments or simulations include defect analysis, inspection and process control; critical dimension, photomask, overlay, nanoparticle, thin film, and 3D interconnect metrologies; line-edge roughness measurements; and nanoscale movements of parts in MEMS/NEMS. Industries that could benefit include semiconductor, data storage, photonics, biotechnology, and nanomanufacturing. TSOM is relatively simple and inexpensive, has a high throughput, and provides nanoscale sensitivity for 3D measurements with potentially significant savings and yield improvements in manufacturing.

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Section: Optimizationmentioning

confidence: 98%

Section: Optimizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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TSOM method for semiconductor metrology

et al. 2011

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“…Many alternative methods have been developed to overcome this limitation, such as scatterometry, confocal microscopy, etc. [1][2][3][4][5] Recently, scatterfield microscopy has demonstrated a potential for improving optical measurement sensitivity and performance. [3][4][5] Scatterfield microscopy combines scatterometry and bright-field optical microscopy, and features Köhler illumination so that an off-axis point in the back focal plane (BFP) of an objective lens makes a plane wave illuminating the sample plane at a specific angle.…”

Section: Introductionmentioning

confidence: 99%

193 nm angle-resolved scatterfield microscope for semiconductor metrology

et al. 2009

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An angle-resolved scatterfield microscope (ARSM) featuring 193 nm excimer laser light was developed for measuring critical dimension (CD) and overlay of nanoscale targets as used in semiconductor metrology. The microscope is designed to have a wide and telecentric conjugate back focal plane (CBFP) and a scan module for resolving Köhler illumination in the sample plane. Angular scanning of the sample plane was achieved by linearly scanning an aperture across the 12 mm diameter CBFP, with aperture size as small as 0.4 mm for some scans. For each aperture, the sample was illuminated over a range of angles from 12° to 48°, corresponding to a numerical aperture of 0.2 to 0.74. Angleresolved measurement results are presented for grating targets with nominal linewidths down to 50 nm.

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“…Through-focus scanning optical microscopy (TSOM) [1][2][3][4][5][6][7][8] allows conventional optical microscopes to collect dimensional information by combining 2D optical images captured at several through-focus positions, transforming a conventional optical microscope into a 3D metrology tool. TSOM is not a resolution enhancement method but an image comparison method and has been demonstrated through simulations to provide lateral and vertical measurement sensitivity of less than a n anometer.…”

Section: Introductionmentioning

confidence: 99%

TSV reveal height and dimension metrology by the TSOM method

Vartanian¹,

Attota

Park

et al. 2013

SPIE Proceedings

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This paper reports on an investigation to determine whether through-focus scanning optical microscopy (TSOM) is applicable to micrometer-scale through-silicon via (TSV) reveal metrology. TSOM has shown promise as an alternative inspection and dimensional metrology technique for FinFETs and defects. In this paper TSOM measurements were simulated using 546 nm light and applied to copper TSV reveal pillars with height in the 3 µm to 5 µm range and diameter of 5 µm. Simulation results, combined with white light interferometric profilometry, are used in an attempt to correlate TSOM image features to variations in TSV height, diameter, and sidewall angle (SWA). Simulations illustrate the sensitivity of Differential TSOM Images (DTI's) using the metric of Optical Intensity Range (OIR), for 5 µm diameter and 5 µm height TSV Cu reveal structures, for variation of SWA (∆ = 2°, OIR = 2.35), height (∆ = 20 nm, OIR = 0.28), and diameter (∆ = 40 nm, OIR = 0.57), compared to an OIR noise floor of 0.01.In addition, white light interferometric profilometry reference data is obtained on multiple TSV reveal structures in adjacent die, and averages calculated for each die's SWA, height, and diameter. TSOM images are obtained on individual TSV's within each set, with DTI's obtained by comparing TSV's from adjacent die. The TSOM DTI's are compared to average profilometry data from identical die to determine whether there are correlations between DTI and profilometry data.However, with several significant TSV reveal features not accounted for in the simulation model, it is difficult to draw conclusions comparing profilometry measurements to TSOM DTI's when such features generate strong optical interactions. Thus, even for similar DTI images there are no discernible correlations to SWA, diameter, or height evident in the profilometry data. The use of a more controlled set of test structures may be advantageous in correlating TSOM to optical images.Keywords: TSOM, Through-focus scanning optical microscopy, metrology, TSV, through silicon via, 3D interconnect critical dimension, optical microscopy INTRODUCTIONThrough-focus scanning optical microscopy (TSOM) [1-8] allows conventional optical microscopes to collect dimensional information by combining 2D optical images captured at several through-focus positions, transforming a conventional optical microscope into a 3D metrology tool. TSOM is not a resolution enhancement method but an image comparison method and has been demonstrated through simulations to provide lateral and vertical measurement sensitivity of less than a n anometer. This performance is comparable to the dimensional measurement sensitivity of critical dimension (CD) metrology tools such as critical dimension scanning electron microscopy (CD-SEM) and optical critical dimension (OCD). TSOM has shown promise as an inspection and dimensional metrology technique for FinFETs and defects [9], where CD-SEM or bright-field inspection, respectively, are currently used. These simulations indicate that the technique is capable of meas...

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Optical through-focus technique that differentiates small changes in line width, line height, and sidewall angle for CD, overlay, and defect metrology applications

Cited by 21 publications

References 10 publications

TSOM method for semiconductor metrology

TSOM method for semiconductor metrology

193 nm angle-resolved scatterfield microscope for semiconductor metrology

TSV reveal height and dimension metrology by the TSOM method

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