We have used a new low-energy electron diffraction (LEED) detector, that features a low beam current electron gun, to investigate for the first time the LEED intensities arising from a water-surface adsorption system. H2O adsorption structures are very sensitive to electron radiation damage. A disordered monolayer of H2O molecules is formed on Pt(111) at 160 K. Upon further exposure an ordered multilayer film is grown that yields new diffraction spots. The periodicity of the diffraction pattern of the multilayer structure is compatible with the model of a molecular ice crystal. Preliminary intensity versus energy spectra of the ‘‘ice crystal’’ are presented. The film thickness is estimated to be well above 10 Å.

The multilayer relaxation of the Ft(210) stepped and kinked surface is analyzed by low-energyelectron diffraction. This is the first appUcation of the new real-space multiple-scattering theory of LEED, designed specifically for such open surfaces where conventional theories fail. Combined with an automated tensor LEED method, it efficiently detects nonalternating atomic relaxations which are oriented primarily perpendicular to the surface. These relaxations are in qualitative agreement with new embedded-atom-method results.PACS numbers: 61.14. Hg, 68.35.Bs, 82.65.Jv Few structures of stepped surfaces have been determined on the sub-A scale, despite their great importance in fields as diverse as catalysis, crystal grow^th, crack propagation, and tribology [ll. In particular, multilayer relaxations and adsorption geometries are expected to be crucial in the understanding of many phenomena involving stepped surfaces.The step structures which have so far been analyzed mainly concern relatively low-Miller-index metal surfaces, in which the terraces between steps are very narrow [2]. A rare exception is Cu{410), studied by low-energy ion scattering [3] [the fee (410) surface dififers from (210) only in that the (100)-oriented terraces are 3 times wider]. While this Cu(410) study does not provide much reliable detail, relaxations of step edge atoms are proposed on the scale of 0.18 A, such that the surface is made smoother. It is now generally accepted that relaxations of the atomic positions occur particularly at steps, including multilayer relaxations deeper into the surface.The primary technique used to analyze steps has been low-energy-electron diffraction (LEED) [4]. Progress with LEED has, however, been hampered by diflftculties in dealing with small interlayer spacings due to the stepped nature of the surface. Small spacings result from wide terraces and from kinks in the steps (kinks are nonalignments of step atoms, giving jagged step edges).The Al(210) surface structure, very similar to that of Pt(210), was analyzed some years ago with LEED by Adams et al. [5] using the relatively robust layerdoubling method [4]. This was, however, only possible because of the unusually weak multiple scattering of electrons in aluminum, which permitted layer doubling to converge better than in almost any other metal. By contrast, platinum causes particularly strong multiple scattering and thus serves as a severe test case for a LEED theory. Several approaches [6-10] have been proposed in order to overcome these difliiculties in LEED theory; the most recent ones [9,10] are based on the new real-space multiple-scattering theory (RSMST) [10]. Using RSMST, LEED intensities can be calculated under conditions where conventional methods fail. For instance, in the case of Ft(210), the layer-doubling method failed to converge suflficiently well for us to determine the surface structure. The structure could, however, be solved by applying the new method, coupled with an automated tensor LEED search [11,12] for the many unknown structu...

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Continuously increasing complexity of semiconductor manufacturing processes drives the need for wafer to wafer and even within wafer control loops metrology. Applying Virtual Metrology (VM) techniques is one promising approach to reduce the time between process, measurement and corrective actions. Prior to implementation -besides technical aspects like testing -the investment into VM has to be assessed and justified on the basis of reliable and reasonable data. This paper presents the investment assessment for implementing VM algorithms into plasma etcher tools of a model semiconductor fabrication line. Core of the investment calculation is a spreadsheet-based calculation which allows for a results per quarter evaluation. A Discrete Event Simulation (DES) model was developed to produce relevant input data for the spreadsheet calculation. Potential risks -e.g., delivery of wrong VM results -due to the implementation of VM have been identified and evaluated using the standardized method of Failure Mode and Effects Analysis (FMEA). INTRODUCTION AND MOTIVATIONCurrently, Integrated Device Manufacturers (IDM) face a continuous increase in the complexity of processes as well as the requirements of shorter life cycles and faster ramps. Challenges like these are driven by Moore's Law (Moore 1965) and more recently by the More Than Moore movement. IDMs have to improve equipment and process control to maintain their competitiveness and to keep up with competitors from emerging market countries.

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