Development of a combined XRF/XPS surface-analysis system for the surface-layer quantification of 28Si spheres

<p class="Abstract">To achieve a new kilogram definition using the X-ray crystal density method, the Center for Measurement Standards, Industrial Technology Research Institute in Taiwan has established the combined XRF (X-ray fluorescence)/XPS (X-ray photoelectron spectroscopy) surface analysis system for the quantitative surface-layer analysis of Si spheres. The surface layer of a Si sphere is composed primarily of an oxide layer, carbonaceous contamination and physisorbed/chemisorbed water. This newly combined instrument has been implemented to measure the XRF for the direct determination of the mass deposition of oxygen (ng/cm²) with a calibrated silicon drift detector and the XPS for the ratio between the elements (O, Si, C) and composition identification. These two complementary methods of X-ray metrology allow an accurate determination of the surface-layer mass of the Si sphere. In this paper, the construction of a combined XRF/XPS surface-analysis system is reported, including the surface characterisation method, the assembly of parts of the load-lock chamber and ultra-high-vacuum analysis chamber, the vacuum-system design, hardware integration and the intended research on surface-layer measurement. It is anticipated that the measured surface-layer mass will be combined with the core mass of the Si sphere.</p>

The Adsorption of Cu Species onto Pyrite Surface and Its Effect on Pyrite Flotation

The adsorption of Cu species onto pyrite surface and its effect on flotation were investigated by using microflotation tests, first-principle calculations, and XPS surface analysis. The results indicated that the flotation of pyrite appears to be activated with CuSO4only at alkaline pH, while being depressed at acidic and neutral pH. The adsorption of copper ions on pyrite surface was pH-dependent, and the adsorption magnitude of copper ions at alkaline pH is higher than that at acidic and neutral pH due to a strong interaction between O atom in Cu(OH)2and surface Fe atom except for the interaction between Cu atom and surface S atom. At acidic and neutral pH, there is only an interaction between Cu atom and surface S atom. The adsorption was relatively weak, and more copper ions in solution precipitated the collector and depressed the flotation of pyrite. XPS analysis confirmed that more copper ionic species (Cu(I) and Cu(II)) are adsorbed on the pyrite surface at alkaline pH than that at acidic and neutral pH.

Studies on a Qualification Method (OSSD) for Microchip Al Bondpads

In authors’ previous paper, an OSAT [Optical, SEM (Scanning Electron Microscopy), Auger (Auger Electron Spectroscopy) and TEM (Transmission Electron Microscopy)] methodology was developed for qualification of microchip aluminum (Al) bondpads. Using the OSAT methodology, one can qualify microchip Al bondpads. In this paper, we will further study the NSOP (Non-Stick On Pad) problem on microchip Al bondpads. A new qualification methodology, OSSD [(Optical, SEM, and Surface and Depth profiling X-ray Photoelectron Spectroscopy (XPS)] will be proposed, in which XPS surface analysis is used to check the contamination level of fluorine and carbon on bondpad surfaces instead of Auger analysis. XPS depth profiling analysis will also be used to measure Al oxide thickness instead of TEM analysis. By using OSSD, Al bondpads can be qualified with both reduced costs and shortened turnaround times versus OSAT.