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

Abstract

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.

WSi 2 /Si multilayer sectioning by reactive ion etching for multilayer Laue lens fabrication

“…and 0.25" thick were comprised of boron-doped silicon and hot-pressed WSi 2 . Although the structure of an MLL necessarily contains a layer thickness depth-gradient, which satisfies the Fresnel zone plate law, the multilayer structures utilized for this particular study do not follow a regular stacking sequence and were designed for a different purpose 9 . Initial tests utilized very simple periodic multilayer structures, and the final performance reported here used a binary pseudorandom stacking sequence with thickness variation between 3 to 100nm and a total growth thickness of between 1 and 6.4 microns.…”

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

“…11,12 The technique has been proven to be 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, as well as scanning and transmission electron microscopes (SEM and TEM, respectively). [12][13][14][15][16][17][18] BPR sequences and arrays are 1D and 2D patterns, respectively, of statistically independent and uniformly distributed binary elements (1's and 0's or -1's and +1's). We use the term 'pseudo-random' to emphasize that the distributions are generated by mathematically precise rules to be random in a mathematically strong sense.…”

Advanced environmental control as a key component in the development of ultrahigh accuracyex situmetrology for x-ray optics

“…The instrumentation includes two slope measuring long-trace profilers, the LTP-II 34 and DLTP, 35 a 6-in. aperture interferometer, a ZYGO™ GPI, 40 two interferometric microscopes, a ZYGO™ NewView-7300 41,42 and a MicroMap™-570, 43 an atomic force microscope, a Veeco™ Dimension-3100, 44 an optical microscope, a NIKON™ MM-800/L, a differential laser Doppler vibrometer, a Polytec™ OFV-5000/OFV-552 (not shown in Fig. 3), and various systems for development and characterization of new x-ray optics, optics and mechanical systems, as well as for testing and calibration of the metrology instrumentation.…”

“…In order to increase the application range and imply an original method for calibration of the instrumental modulation transfer function (MTF) (see Ref. 40 and references therein), we have developed a procedure and dedicated software for power spectral density (PSD) analysis of MicroMap™ measurements. 59 The PSD analysis enables measurements of groove density distributions of diffraction gratings as suggested and first realized in Ref.…”

“…The problem can be addressed via application of MTF calibration similar to one realized for other types of metrology instrumentation. 40 4 Improvement of Performance of the Developmental Long Trace Profiler After moving into the new lab, the DLTP was upgraded to optimize the measurements with side facing optics. 58 Figure 6 shows the experimental arrangement of the upgraded DLTP in the XROL.…”