White light interferometry for quantitative surface characterization in ion sputtering experiments

Abstract

White light interferometry (WLI) can be used to obtain surface morphology information on dimensional scale of millimeters with lateral resolution as good as ∼1 µm and depth resolution down to 1 nm. By performing true three-dimensional imaging of sample surfaces, the WLI technique enables accurate quantitative characterization of the geometry of surface features and compares favorably to scanning electron and atomic force microscopies by avoiding some of their drawbacks.In this paper, results of using the WLI imaging technique to characterize the products of ion sputtering experiments are reported. With a few figures, several example applications of the WLI method are illustrated when used for (i) sputtering yield measurements and time-to-depth conversion, (ii) optimizing ion beam current density profiles, the shapes of sputtered craters, and multiple ion beam superposition and (iii) quantitative characterization of surfaces processed with ions.In particular, for sputter depth profiling experiments of 25 Mg, 44 Ca and 53 Cr ion implants in Si (implantation energy of 1 keV per nucleon), the depth calibration of the measured depth profile curves determined by the WLI method appeared to be self-consistent with TRIM simulations for such projectile-matrix systems. In addition, high depth resolution of the WLI method is demonstrated for a case of a Genesis solar wind Si collector surface processed by gas cluster ion beam: a 12.5 nm layer was removed from the processed surface, while the transition length between the processed and untreated areas was 150 µm.

High‐resolution secondary ion mass spectrometry depth profiling of nanolayers

“…To achieve this pre‐alignment, a Faraday cup was used for ion beam collection which took advantage of available crater imaging capabilities. Crater imaging was carried out in situ by an optical Schwarzschild‐type microscope and scanning electron microscopy or by ex situ optical white light interferometry (Fig. (b)).…”

Single-crystal diamond refractive lens for focusing X-rays in two dimensions

“…The second paraboloid was machined with the laser power scaled to maintain a separation of at least 40 mm. This is why the paraboloids had different radii of curvature (100 and 109 mm) as measured by whitelight interferometry (WLI) using an optical profilometer MicroXAM-1200 (Baryshev et al, 2012). WLI could not automatically reconstruct the three-dimensional profile of the lenses due to poor reflectivity in the direction normal to the surface and high diamond transparency.…”

Measuring the roughness of buried interfaces by sputter depth profiling

“…Both raster areas were precisely overlapped by using an in situ Schwarzschild microscope, 17 and ex situ by white light profilometry. 21 Ion beam currents were measured and focused in situ by a custom made graphite Faraday cup (FC) consisting of an internal pin and inlet holes of 250 µm dia. on the mask.…”

“…Ion beam profiles were checked and known to have a symmetric Gaussian distribution by burning dents in soft materials and profiling the dents by ex situ white light profilometry. 21 It allows one to precisely calculate a current density of an ion beam using a known dc current value measured on the FC. The milling beam parameters at 500 eV were 1 µA dc and a FWHM of Gaussian-like beam profile of ∼150 µm.…”