XPS analysis of FIB‐milled Si

Abstract

The development of focused ion beam (FIB) workstations with beam sizes <10 nm in diameter has initiated a revolution in the modification and characterization of materials on a nanoscale. Focused ion beams are now widely used to obtain site-specific specimens for scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses, but are being utilized also in connection with Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS). In order to understand the structure/property relationships of new materials, it is imperative that nano-characterization techniques with site-specific precision be available. In this work, x-ray photoelectron spectroscopy and imaging are used to study the surface changes that occur due to FIB milling of Si(100). The FIB-prepared specimen was analyzed 'as received' and after the specimen was stored at room temperature and in the atmosphere for 5 months. The XPS images were acquired to determine the distribution of Si 4+ (SiO 2 ) and Ga contamination on the Si 0 surface. Small-area XPS spectra of the Si FIB specimen were collected to evaluate the changes in SiO 2 surface concentration. The XPS spectra were also extracted from areas ∼1 µm × 1 µm by exploiting the images-to-spectra approach to XPS analysis. This study demonstrates both the problems inherent in the analysis of small samples and the critical information that can be obtained from high spatial resolution XPS analysis. In this example, increased SiO 2 was observed in the 'aged' sample relative to the 'as-received' sample, and non-uniform Ga contamination was detected.

Theory and New Applications ofEx SituLift Out

“…Although electron transparent EXLO specimens are most often analyzed by S/TEM, thicker lift out specimens may be viewed by surface-sensitive techniques such as X-ray photoelectron spectroscopy or secondary ion mass spectrometry, or by SEM methods (Stevie et al, 2001;Ferryman et al, 2002;Rossie et al, 2002;Prasad et al, 2003Prasad et al, , 2009. EXLO of site specific thick specimens optimizes imaging incident angles and analytical collection angles, which may be compromised or impossible to obtain due to confined trenches of conventional FIB milled cross sections.…”

XPS spectromicroscopy: exploiting the relationship between images and spectra

“…More recently, however, a number of publications have described the acquisition of spectrum image datasets, [2] where each pixel in an image contains a spectrum. Such datasets may be acquired by scanning an X-ray probe over the surface while acquiring a spectrum at each pixel, or by acquiring a series of energy-filtered images incremented in energy, known as parallel imaging.…”

“…Indeed, even as a guide to selected area analysis, single energy images perform poorly, since they can only truly represent changes occurring across an image if there are only two components which change. Yet the acquisition of quantifiable chemical state images is clearly preferable to analyses at a number of discrete points.More recently, however, a number of publications have described the acquisition of spectrum image datasets, [2] where each pixel in an image contains a spectrum. Such datasets may be acquired by scanning an X-ray probe over the surface while acquiring a spectrum at each pixel, or by acquiring a series of energy-filtered images incremented in energy, known as parallel imaging.…”

FIB/DualBeam Techniques for Quantitative Analyses

“…The basic FIB lift-out techniques have also been employed to prepare samples for quantification in surface science instruments such as x-ray photoelectron spectroscopy [5], Auger electron spectroscopy [6], secondary ion mass spectroscopy (SIMS) [6], as well as 3D atom probe [7,8]. The same techniques used to prepare atom probe specimens can be used to make pillar-shaped TEM specimens for on-axis TEM tomography [9,10].…”