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

Abstract

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.

Development of a high performance surface slope measuring system for two-dimensional mapping of x-ray optics

“…It is for this reason that the XROL is a critical partner in the development of metrology for next-generation optics, and many R&D projects are underway in close collaboration with the x-ray optical teams at x-ray facilities in U.S.A. and around the world, as well as with the U.S.A. industry (see Refs. [16][17][18][19][20][21][22] and references therein).…”

Reliability investigation of the instrument transfer function calibration technique based on binary pseudo-random array standards

“…From that time, a broad variety of BPR test standards with the elementary sizes from 1.5 nanometers and up to the dozens of microns have been developed and successfully applied for resolution calibration of the electron, x-ray, and optical microscopes, optical scatterometers, and large-aperture Fizeau interferometers (see, for example, Refs. [9][10][11][12][13][14][15][16][17] and references therein).…”

An ultrahigh-resolution soft x-ray microscope for quantitative analysis of chemically heterogeneous nanomaterials

“…We quantify the achieved spatial resolution of our microscope by measuring both one-dimensional and two-dimensional objects of known structure and composition. First, we study a binary pseudorandom multilayer pattern made of alternating layers of WSi 2 and Si with a minimum layer width of 3 nm (20,21). We image the structure with 10-ms exposures of 1300-eV x-rays and 0.95-nm wavelength.…”