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In-Line Metrology
Published in Robert Doering, Yoshio Nishi, Handbook of Semiconductor Manufacturing Technology, 2017
The traditional model of an oxide layer on a silicon substrate is that of a single, flat layer that has a sharp interface with the silicon below. This layer has also been referred to as a slab. Although an interfacial layer with different physical and chemical properties is present after SiO2 or SiOxNy is grown, a comparison of the precision of optical models for SE systems has shown that including the interfacial layer usually results in a larger (worst) precision than modeling the entire film as a single layer (or slab) [48]. Attempts at modeling using an interfacial layer composed of a Bruggerman Effective Medium Approximation (BEMA) model, provides a better Goodness-Of-Fit to the experimental data but a larger precision [48]. These effects are due to too much of correlation between fit variables and usually result in unrealistic values. Alternative single layer models (without an interfacial layer) are used that provide better precision values without sacrificing the Goodness-Of-Fit. Since SWE provides improved (i.e., smaller values) precision for these thin films, the optical constant for a single SiO2 or SiOxNy layer is used. This approach assumes that the nitrogen concentration and depth profile remain uniform across the wafer and from wafer to wafer. The accuracy of oxynitride film thickness depends on the accuracy of the optical constants for that film. According to the ITRS, if the gate dielectric EOT is 1.0 nm thick and the process tolerance is 5% for 3σ (process variation), then P/T = 10% = 6σ/(0.1 nm) which gives a measurement variation 3σ = 0.004 nm. This precision can be achieved by desorbing the surface contamination layer that adsorbs on the wafer surface prior to measurement. A number of approaches have been made commercially available including use of infra-red laser irradiation and thermal desorption [49].
Evaluation of structural performance and energy saving ability of normal, voided and foamed RC slabs
Published in HBRC Journal, 2019
Suzan A. A. Mustafa, Ebtsam Fathy, Mohamed A. Essa, Amal A.E. Mohammed
To examine structural performance of different types of roof slabs, modal and static analyses were performed. Modal analysis helped in getting slabs’ natural frequencies, while static analysis helped in studying slabs’ deflections and stresses. The dead load was taken into consideration in elements properties for both types of analyses. The effect of temperature gradient obtained from thermal analysis was considered in material properties for modal analysis while in static analysis the temperature effect was taken into consideration in both material properties and as non-uniform temperature distribution through the thickness of the slabs. The imposed load was considered in static analysis according to the Egyptian code for calculating loads and forces (ECP201-2012) [34] and it was applied on the mesh nodes of the top surface of the slab. The performance of the slabs was evaluated by comparing the response at reference temperature (Rref. temp.) and after applying temperature gradient in summer and winter days (Rnon-uniform. temp.), where the change was calculated according to the following equation
Carbonatites: related ore deposits, resources, footprint, and exploration methods
Published in Applied Earth Science, 2018
George J. Simandl, Suzanne Paradis
Most carbonatites and alkaline-carbonatite complexes are emplaced in continental (88% cratonic, 10.5% non-cratonic) settings (Figures 3–4) in Archean and Proterozoic rocks, or in Phanerozoic rocks underlain by a Precambrian basement (Sage and Watkinson 1991; Woolley and Kjarsgaard 2008a; Pirajno 2015). They form in extensional tectonic settings (Bailey 1974, 1977, 1992), along major linear trends related to large-scale intra-plate fracture zones, in association with doming features (crustal arching), or in relation to slab windows in subducting plates (Duke 2009; Duke et al. 2014). The link between these tectonic features and intense magmatic activity means that many carbonatites are also temporally and spatially related to ‘large igneous provinces’ (Pirajno 2000; Ernst and Bell 2010). Some researchers (e.g. Nelson et al. 1988; Bell 2001, 2005; Pirajno 2015) consider mantle plumes essential to carbonatite genesis.