Binary pseudo-random gratings and arrays for calibration of the modulation transfer function of surface profilometers: recent developments

Barber, Sarah; Soldate, Paul; Anderson, Erik H.; Cambie, Rossana; Marchesini, Stefano; McKinney, Wayne R.; Takacs, Peter Z.; Voronov, Dmitriy L.; Yashchuk, Valeriy V.

doi:10.1117/12.825389

Cited by 13 publications

(20 citation statements)

References 24 publications

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“…For such verification of optical surface profilometers in the spatial frequency domain, a modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) gratings and arrays has been suggested [1][2][3] and proven to be an effective calibration method for a number of interferometric microscopes, a phase shifting Fizeau interferometer, and a scatterometer [4].…”

Section: Introductionmentioning

confidence: 99%

Characterization of electron microscopes with binary pseudo-random multilayer test samples

Yashchuk

Conley

Anderson

et al. 2011

Nuclear Instruments and Methods in Physics Research Section A:

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Abstract:Verification of the reliability of metrology data from high quality x-ray optics requires adequate methods for test and calibration of the instruments be developed. For such verification of optical surface profilometers in the spatial frequency domain, a modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) gratings and arrays has been suggested [1-3] and proven to be an effective calibration method for a number of interferometric microscopes, a phase shifting Fizeau interferometer, and a scatterometer [4].Here we describe the details of development of binary pseudo-random multilayer (BPRML) test samples suitable for characterization of scanning (SEM) and transmission (TEM) electron microscopes. A BPRML sample is a multilayer structure consisting of two materials with significantly different contrasts when observed with an electron microscope. The thicknesses of the layers are distributed according to a binary pseudo-random sequence. For the MTF calibration of an electron microscope, an image of the BPR multilayer cross-section, measured with the microscope, is processed to get a power spectral density (PSD) distribution. The MTF is found as the square root of the ratio of the PSD spectrum measured with the BPRML to the 'ideal', spatial frequency independent, PSD spectrum, inherent for a precisely fabricated BPRML.We discuss the results of SEM and TEM measurements with the BPRML test samples fabricated from a BPRML (WSi 2 /Si with fundamental layer thickness of 3 nm) with a Dual Beam FIB (focused ion beam)/SEM technique. In particular, we demonstrate that significant information about the metrological reliability of the TEM measurements can be extracted even when the fundamental frequency of the BPRML sample is smaller than the Nyquist frequency of the measurements. The measurements demonstrate a number of problems related to the interpretation of the SEM and TEM data. Note that similar BPRML test samples can be used to characterize x-ray microscopes. Corresponding work with x-ray microscopes is in progress. References:[1] V

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Section: Introductionmentioning

confidence: 99%

Characterization of electron microscopes with binary pseudo-random multilayer test samples

Yashchuk

Conley

Anderson

et al. 2011

Nuclear Instruments and Methods in Physics Research Section A:

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“…The success of applying this method to different interferometric microscopes and a scatterometer has been experimentally demonstrated. [20][21][22][23][24] In the present work, we present results of extending the BPRA method to large field-of-view interferometers, a class of instruments that are, and will continue to be, a standard for making high precision surface height measurements over relatively low spatial frequency ranges from approximately 10 -2 mm -1 to 10 mm -1 . An extension of the method to the micro-and nano-scale measurements with scanning and transmission electron microscopes (SEM and TEM, respectively) is also presented.…”

Section: Measured Psdmentioning

confidence: 99%

“…2.5× and 5× objectives. 22,24 In these cases waviness of the substrate tended to distort the measured PSDs from the PSDs expected to result from the mathematical properties of the BPRA. The solution to this problem was to etch the BPRAs into a super polished silicon substrate.…”

Section: Bpra Fabricationmentioning

confidence: 99%

“…Because the PSD from a BPR grating or array is a result of the groove distribution, it is not particularly sensitive to the groove shape or roughness of the groove surfaces, top or bottom. 24 The only requirement is that the value of 0 h should be large enough to ensure a negligible contribution from fabrication imperfections to the PSD measurements. Figure 1b illustrates a design of a BPR multilayer (ML) test sample suitable for measurements with electron microscopes.…”

mentioning

confidence: 99%

“…For more details on the URA generation algorithm see Refs. 42,43 1D and 2D BPR gratings and arrays which we use for MTF calibration of surface profilometers (such as interferometric microscopes, [21][22][23][24] scatterometers, 23 and, now, large area interferometers) are sets of rectangular grooves pseudo-randomly distributed over a uniform 1D and 2D grid, respectively. Figure 1a h , determines the amplitude of the array's inherent PSD spectrum.…”

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Calibration of the modulation transfer function of surface profilometers with binary pseudo-random test standards: expanding the application range

et al. 2010

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A modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) gratings and arrays [Proc. SPIE 7077-7 (2007), Opt. Eng. 47(7), 073602-1-5 (2008)] has been proven to be an effective MTF calibration method for a number of interferometric microscopes and a scatterometer [Nucl. Instr. and Meth. A 616, 172-82 (2010]. Here we report on a significant expansion of the application range of the method. We describe the MTF calibration of a 6 inch phase shifting Fizeau interferometer. Beyond providing a direct measurement of the interferometer's MTF, tests with a BPR array surface have revealed an asymmetry in the instrument's data processing algorithm that fundamentally limits its bandwidth. Moreover, the tests have illustrated the effects of the instrument's detrending and filtering procedures on power spectral density measurements. The details of the development of a BPR test sample suitable for calibration of scanning and transmission electron microscopes are also presented. Such a test sample is realized as a multilayer structure with the layer thicknesses of two materials corresponding to BPR sequence. The investigations confirm the universal character of the method that makes it applicable to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.

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Binary pseudo-random patterned structures for modulation transfer function calibration and resolution characterization of a full-field transmission soft x-ray microscope

Yashchuk

Fischer

Chan

et al. 2015

Review of Scientific Instruments

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We present a modulation transfer function (MTF) calibration method based on binary pseudo-random (BPR) onedimensional sequences and two-dimensional arrays as an effective method for spectral characterization in the spatial frequency domain of a broad variety of metrology instrumentation, including interferometric microscopes, scatterometers, phase shifting Fizeau interferometers, scanning and transmission electron microscopes, and at this time, x-ray microscopes. The inherent power spectral density of BPR gratings and arrays, which has a deterministic white-noise-like character, allows a direct determination of the MTF with a uniform sensitivity over the entire spatial frequency range and field of view of an instrument. We demonstrate the MTF calibration and resolution characterization over the full field of a transmission soft x-ray microscope using a BPR multilayer (ML) test sample with 2.8-nm fundamental layer thickness. We show that beyond providing a direct measurement of the microscope's MTF, tests with the BPRML sample can be used to fine tune the instrument's focal distance. Our results confirm the universal character of the method indicating its applicability to a large variety of metrology instrumentation with spatial wavelength bandwidths from a few nanometers to hundreds of millimeters.

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Binary pseudo-random gratings and arrays for calibration of the modulation transfer function of surface profilometers: recent developments

Cited by 13 publications

References 24 publications

Characterization of electron microscopes with binary pseudo-random multilayer test samples

Characterization of electron microscopes with binary pseudo-random multilayer test samples

Calibration of the modulation transfer function of surface profilometers with binary pseudo-random test standards: expanding the application range

Binary pseudo-random patterned structures for modulation transfer function calibration and resolution characterization of a full-field transmission soft x-ray microscope

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