TSOM method for semiconductor metrology

Attota, Ravikiran; Dixson, Ronald G.; Kramar, John A.; Potzick, James E.; Vladár, András; Bunday, Benjamin; Novak, Erik; Rudack, Andrew C.

doi:10.1117/12.881620

Cited by 26 publications

(33 citation statements)

References 12 publications

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“…Some of the most widely used configurations are single incidence angle reflectometry, 2-Θ scatterometry, spectroscopic ellipsometry, Fourier scatterometry, interferometric Fourier scatterometry,etc., [7][8][9][10][11][12][13][14][15] with a wide range of applications [16][17][18][19][20]. In an earlier paper, it has been predicted theoretically how, and under which conditions, CFS can be more sensitive than the classical IOS [21].…”

Section: Introductionmentioning

confidence: 99%

Reconstruction of sub-wavelength features and nano-positioning of gratings using coherent Fourier scatterometry

et al. 2014

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Abstract:Optical scatterometry is the state of art optical inspection technique for quality control in lithographic process. As such, any boost in its performance carries very relevant potential in semiconductor industry. Recently we have shown that coherent Fourier scatterometry (CFS) can lead to a notably improved sensitivity in the reconstruction of the geometry of printed gratings. In this work, we report on implementation of a CFS instrument, which confirms the predicted performances. The system, although currently operating at a relatively low numerical aperture (NA = 0.4) and long wavelength (633 nm) allows already the reconstruction of the grating parameters with nanometer accuracy, which is comparable to that of AFM and SEM measurements on the same sample, used as reference measurements. Additionally, 1 nm accuracy in lateral positioning has been demonstrated, corresponding to 0.08% of the pitch of the grating used in the actual experiment.

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Section: Introductionmentioning

confidence: 99%

Reconstruction of sub-wavelength features and nano-positioning of gratings using coherent Fourier scatterometry

et al. 2014

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“…In this paper, we use "TSOM image" to refer to these 2D TSOM cross-sectional images. As demonstrated in previous work [8], TSOM images are collected as discussed above, and differential TSOM images are calculated to observe the effects of subtle perturbations in the properties of the measurand. Three important properties of TSOM images have been demonstrated:…”

Section: Tsom Image Methodsmentioning

confidence: 99%

“…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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“…If the two TSOM images are obtained using two targets with slightly different dimensions, then the D-TSOM image color pattern highlights the type of dimensional difference between the two targets [10, 19, 22]. If the two TSOM images are obtained using the same target (similar to the repeated collection), then the D-TSOM image highlights noise [10, 17, 53], including optical and vibrational noise.…”

Section: Tsom Imaging Methodsmentioning

confidence: 99%

Fidelity test for through-focus or volumetric type of optical imaging methods

Attota¹

2018

Opt. Express

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Rapid increase in interest and applications of through-focus (TF) or volumetric type of optical imaging in biology and other areas has resulted in the development of several TF image collection methods. Achieving quantitative results from images requires standardization and optimization of image acquisition protocols. Several standardization protocols are available for conventional optical microscopy where a best-focus image is used, but to date, rigorous testing protocols do not exist for TF optical imaging. In this paper, we present a method to determine the fidelity of the TF optical data using the TF scanning optical microscopy images.

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TSOM method for semiconductor metrology

Cited by 26 publications

References 12 publications

Reconstruction of sub-wavelength features and nano-positioning of gratings using coherent Fourier scatterometry

Reconstruction of sub-wavelength features and nano-positioning of gratings using coherent Fourier scatterometry

TSV reveal height and dimension metrology by the TSOM method

Fidelity test for through-focus or volumetric type of optical imaging methods

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