Browsing by Author "Hoffmann, N."

To study mass transport phenomena in advanced microelectronic devices With X-rays requires penetration of dielectric and Si layers up to 30 mum thick. X-ray imaging at 1.8 keV photon energy provides a high amplitude contrast between Cu or Al interconnects and dielectric layers and can penetrate through the required thickness. To perform Xray microscopy at 1.8 keV, a new Ru/Si multilayer was designed for the transmission X-ray microscope XM-1 installed at the Advanced Light Source in Berkeley. The mass flow in a passivated Cu interconnect was studied at current densities up to 10(7) A/cm(2). In addition, we demonstrated the high material contrast from different elements in integrated circuits with a resolution of about 40 nm. (C) 2002 Elsevier Science B.V. All rights reserved.

In an even-aged mono-specific stand we evaluated the use of unclassified point clouds from single- and multiple-scan terrestrial laser scanning as a tool to determine various attributes of growing space and neighborhood structure of fifteen Metasequoia glyptostroboides (Hu.) trees. It was found that almost all tested attributes were related to diameter increment at breast height (Di) of the target tree, but also to diameter at breast height itself (DBH). A comparison of various additive models that accounted for the additional explanatory power of attributes other than DBH revealed that measures of space filling were most suitable estimators of Di. Upside-down search cones fixed at low heights in the stand performed best to explain Di, which is in contrast to previous studies that recommended the use of search cones fixed at greater heights in the tree. Surprisingly, we found search-cones fixed at 60% of the tree height to be more closely related with diameter increment at that height (Di60%) than with Di. Furthermore, our study revealed that multiple-scan based measurements of space filling in the neighborhood of a tree should always be favored over single-scan measurements due to their generally higher quality and greater comprehensiveness in the representation of a forest scene.

X-ray imaging of electromigration in a passivated Cu interconnect was performed with 100-nm spatial resolution. A time sequence of 200 images, recorded with the European Synchrotron Radiation Facility x-ray microscope in 2.2 h at 4 keV photon energy, visualizes the mass flow of Cu at current densities up to 2x10(7) A/cm(2). Due to the high penetration power through matter and the element specific image contrast, x-ray microscopy is a unique tool for time-resolved, quantitative mass transport measurements in interconnects. Model calculations predict that failures in operating microprocessors are detectable with 30 nm resolution by nanotomography. (C) 2001 American Institute of Physics.

We consider moduli schemes of vector bundles over a smooth projective curve endowed with parabolic structures over a marked point. Boden and Hu observed that a slight variation of the weights leads to a desingularisation of the moduli scheme, and they conjectured that one can always obtain a small resolution this way. The present text proves this conjecture in some cases (including all bundles of rank up to eight) and gives counterexamples in all other cases (in particular in every rank beyond eight). The main tool is a generalisation of Ext-groups involving more than two quasiparabolic bundles.