Results 1 - 10 of 2951
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[en] The use of norbornene-based polysulfones as non-chemically amplified resists (non-CARs) for 193 nm immersion lithography was explored. Allylbenzene was incorporated into the polymer backbone to increase the absorbance of the polymers. The effect of polymer absorbance on sensitivity to 193 nm radiation was investigated. Polymer films on silicon wafers have been irradiated with 193 nm photons in the absence of a photo-acid generator. Chemical contrast curves (film thickness versus dose plots prior to solvent development) and contrast curves (film thickness versus dose plots after solvent development) were obtained by spectroscopic ellipsometry. The results show that E0 values could be reduced significantly by increasing the absorbance of the polymer.
[en] Attenuated total internal reflection ellipsometry was used to probe the molecular orientation and switching near the surface of a smectic liquid crystal cell showing V-shaped switching. We find that the switching occurs collectively near the surface as in the bulk. The molecules form a twisted state, but the twist angle relative to the bulk layer normal is small because of compensating twist of the smectic layer normal. As a result, a rather uniform molecular orientation is produced, resulting in high extinction and a high contrast ratio in the absence of a field
[en] While optical spectroscopic measurements using ellipsometry may be made in air and are non-destructive, the relatively large (> 2 mm) spot size has limited their use to surface regions greater than 2 mm in lateral extent. Recent developments in focusing instruments have made spot sizes on the order of 20 to 25 μm possible. The work to be presented explores the use of the 25 μm spot size to probe non-uniform nanostructured thin films. Measurements were performed on a highly non-uniform film (0 to 2 μm in thickness across 4 mm in lateral dimension) using such a 25 μm spot. Further reduction of the spot size is possible using mechanical masking with a slit. Measurements have been made to the range of a few microns in width. The practical resolution limits of beam masking may be decreased by increasing incident light intensity, improving slit alignment, and improving detection methods
[en] We review recent advances in optical and magnetooptical (MO) scatterometry applied to periodically ordered nano structures such as periodically patterned lines, wires, dots, or holes. The techniques are based on spectroscopic ellipsometry (SE), either in the basic or generalized modes, Mueller matrix polarimetry, and MO spectroscopy mainly based on MO Kerr effect measurements. We briefly present experimental setups, commonly used theoretical approaches, and experimental results obtained by SE and MO spectroscopic analyses of various samples. The reviewed analyses are mainly related to monitoring optical critical dimensions such as the widths, depths, and periods of the patterned elements, their real shapes, and their line edge or linewidth roughness. We also discuss the advantages and disadvantages of the optical spectroscopic techniques compared to direct monitoring techniques.
[en] Because conformations and interactions are intimately linked, the rich phase behavior exhibited by multicomponent polymer-modified interfaces, and in particular multicomponent polymer brushes, offers new opportunities for manipulating interfacial properties. Despite the widespread use of a variety of grafting to and grafting from approaches for making polymer brushes, there are few reports of synthesis and responsive behavior of stratified block copolymer brushes. In this presentation we describe our efforts to create bi-level and random copolymer brushes consisting of poly(N-isopropylacrylamide) and poly(methacrylic acid) using surface initiated, photoiniferter-mediated photopolymerization. Pre-addition of a source of deactivating radicals combined with judicious choice of photopolymerization conditions enables the formation of bi-level brushes. In situ, multi-angle ellipsometry measurements show that the blocks of the bi-level brushes actuate independently to changes in pH and temperature, but respond in concert to changes in ionic strength. Efforts to examine the nanoscale structure of these systems as a function of pH and temperature using neutron reflectometry will also be highlighted.
[en] Silicon-on-insulator (SOI) wafers are semiconductor substrates that can be used in next-generation high-speed and low-power devices. An ultrathin SOI wafer with a SOI layer of less than 20 nm is required for the dynamic random access memory half-pitch node of 100 nm or lower. In this report, the thinning of the SOI layer by numerically controlled plasma chemical vaporization machining is described. A commercial 6 in. SOI wafer was used for the demonstration thinning. Spectroscopic ellipsometry was used to measure the thickness distribution of the SOI layer. The SOI layer thickness of ∼200±4 nm was successfully thinned to 13±2 nm
[en] Ultrafast ellipsometry and transient absorption spectroscopies are used to measure material dynamics under extreme conditions of temperature, pressure, and volumetric compression induced by shock wave loading with a chirped, spectrally clipped shock drive pulse.
[en] Real-time spectroscopic ellipsometry was used to monitor the nucleation behavior of Ge grown on H-terminated Si(100) at 500 deg. C and H-terminated Si(111) with <0.3 deg. and ∼4 deg. miscut angles at 570 deg. C. To model the dielectric functions of layers with space-separated 3D islands the Tauc-Lorentz parametrization (TLP) was used. This parametrization was found to be much better than the generally used Brueggemann effective media approximation. It is shown that the wetting layer (WL) in the system of Ge on flat Si(111) is of nearly constant thickness during island nucleation, whereas the nucleation of Ge islands on stepped Si(111) and Si(100) is accompanied by a strong decrease of the wetting-layer thickness. It is concluded that in the first case 3D islands grow at the expense of atoms adsorbed on the wetting layer surface, whereas in the latter cases 3D islands grow at the expense of atoms of the wetting layer itself, which corresponds to stress-driven nucleation
[en] The optical conductivity spectra of several intermetallic compounds were measured by spectroscopic ellipsometry. Three spectra were measured for each compound; just after the sample was mechanically polished, at high temperature, and after the sample was annealed at 110 .deg. C for at least one day and cooled to room temperature. An equiatomic FeTi alloy showed the typical effects of annealing after mechanical polishing of surface. The spectrum after annealing had a larger magnitude and sharper structures than the spectrum before annealing. We also observed shifts of peaks in the spectrum. A relatively low-temperature annealing gave rise to unexpectedly substantial effects, and the effects were explained by recrystallization and/or a disorder → order transition of the surface of the sample which was damaged and, hence, became highly disordered by mechanical polishing. Similar effects were also observed when the sample temperature was lowered. The observed changes upon annealing could partly be explained by presumption that the recrystallization would be realized in such a way that the average atomic spacing would be reduced
[en] The present Ph.D. thesis consists of nine scientific papers, which have either been published already in international journals or have been submitted for publication. Although different specific subjects are treated in these papers, their common topic is the preparation and characterization of ultrathin films of long-chain hydrocarbon compounds on solid substrates (so-called self-assembled monolayers, SAMs). Paper 1 and 2 deal with the fabrication and structural characterization of adsorbed multilayers, which are linked among each other either through covalent O-Si-O bonds (paper 1) or through ionic Zr4+ bridges (paper 2). The main subject is the influence of various parameters such as chain length, adsorption temperature etc. on the degree of structural order in the deposited films. Paper 3 and 4 focus on the application of ellipsometry for the investigation of SAM films. It is shown that this method allows a direct in-situ monitoring of surface reactions and a determination of refractive indices of ultrathin films through a variation of the surrounding medium. Paper 5 and 6 deal with experimental aspects of atomic force microscopy used in specific instrumental modes (real time in-situ measurements) to study monolayer and submonolayer adsorbates on silicon and mica substrates. In paper 7, internal reflection IR spectroscopy (ATR-IR) is considered as another method for in-situ studies of solid-liquid interfaces. Using a specific, custom-made experimental setup, this technique allows a direct observation of SAM formation and yields real time structural information about the film growth in the course of the adsorption process. Paper 8 and 9, finally, focus on a new, practically useful procedure to prepare ultrathin films of silicon oxide through step-wise adsorption and subsequent oxidation of alkylsiloxane monolayers on silicon and mica substrates, which allows the controlled growth of oxide films with thicknesses between 1 and 10 nm in monolayer increments of 0.3 nm. (author)