Ellipsometry surface roughness

Measurement of such small thicknesses is difficult. Ellipsometry [3] and angle-dependent XPS [5] may be used with care to avoid complications caused by surface roughness. 

The surface roughness of the films is also obtained from ellipsometry. Typical roughness values of 10 A are found for films with optimum CVD growth conditions, while PVD growth conditions lead to a much greater roughness. 

X-ray analysis methods (including diffraction and reflectometry) described in Chap. 1 are the most widely used tools for the identification of crystalline properties of materials, in addition to materials strain, texture, stress, density, and surface roughness—properties that are key parameters for various industrial applications. Chapter 2 covers a wide range of optical characterization techniques with focus on ellipsometry, Raman scattering, Fourier transform infrared spectroscopy, and spectrophotometry. Those methods, covering a wide range of photon energy and laser... 

The porous structure, the void volume and the surface roughness of a film can all be effectively studied using ellipsometry, as the refractive index is a function of the material s density, composition, and morphology. For the structure of a... 

Ellipsometry is very sensitive to sample surface and interface structures. Hence, to incorporate these structures into an optical model for the investigated sample is necessary in ellipsometry data analysis. The effective medium approximation (EMA) [66] has been applied to calculating the complex refractive indices and dielectric constants of surface roughness and interface layers. In addition, the volume fractions in composite materials can be got from ellipsometry analysis using EMA. 

Ellipsometry is an optical monolayer-sensitive interface analysis method for the investigation of various aspects of surface and interfaces, including surface stoichiometry, surface roughness, adsorption, desorption, and surface strain, etc. In combination with the availability of microcomputers, SE has been developed and widely used for studies of thin films in the ambient, where parameters such as film thickness, composition, and interface roughness are determined. SE is now a popular tool for in situ growth control and diagnostics of interfaces. 

Ellipsometry can be sensitive to layers of matter only one atom thick. For example, oxidation of freshly cleaved single-crystal graphite can be monitored from the first monolayer and up. The best thicknesses for the ellipsometric study of thin films are between about 1 nm and 1000 nm. Although the spectra become complicated, films thicker than even 1 pm can be studied. Flat planar materials are optimum, but surface and interfacial roughness can be quantitatively determined if the roughness scale is smaller than about 100 nm. Thus ellipsometry is ideal for the investigation of interfacial surfaces in optical coatings and semiconductor struc-... 

Ellipsometry is a method of measuring the film thickness, refractive index, and extinction coefficient of single films, layer stacks, and substrate materials with very high sensitivity. Rough surfaces, interfaces, material gradients and mixtures of different materials can be analyzed. 

It is easy to figure out why this is. The theory of ellipsometry assumes that the surface is atomically flat. It is possible to model roughness as a series of declivities in the surface. These are taken as being full of solution. Thus, the ellipsometer sees pools of solution where it assumes the electrode surface should be. Especially in the determination of submonolayers, the result can contain significant errors in n and K that have been calculated on the assumption of a completely smooth surface (Brusic and Cahan, 1969). 

Ellipsometry 453 Functional Correlation 557 Reflectivity 1042 Roughness 1080 Surface Parameter 1199... 

Optical techniques can be used to monitor optical thickness and dielectric constant parameters. This includes ellipsometry, multiple reflection interferometry (74), evanescent wave (75), and surface plasmon resonance spectroscopy techniques (43). Ellipsometry has been used widely and routinely to investigate film thickness of pol3mier brush films (76). For optical properties of films, it is important that the average film roughness and imiformity is specified. Often, sampling is localized by the spot size, such that it is necessary to probe and average different areas of a sample. 

The advancing CAs of both water and hexadecane on surfaces of sf-polymethacrylate copolymers with different side chains and molar content of the /-methacrylate show clear influences of both (Figures 11.23a and 11.23b). Note that all thin films on silicon wafer with very low roughness as ensured by ellipsometry and X-ray reflectivity were prepared under comparable conditions by spin-coating from BFMB or chloroform, followed by drying in a vacuum oven at 140°C for several hours. 

Materials. PMMA (Polysciences, MW=60,000, Mw/Mn=1.10), PS (Aldrich, MW=44,000, Mw/Mn=1.10), and PET (Aldrich) films were prepared by spin coating (2000 rpm) 0.25 wt % polymer/solvent solutions onto silicon (100) wafers, which had a native oxide layer. Toluene was used as the solvent for PMMA and PS, and 2-chlorophenol was used for PET. Films were annealed at 100°C under vacuum ( 0.01 torr) for 2 hours and allowed to cool under vacuum. Experiments were performed within days of film coating, and 1 day or less after annealing. Film thicknesses were measured using ellipsometry (Sopra) and found to be approximately 21, 12, and 20 nm ( 5nm), for PMMA, PET, and PS, respectively. Film surfaces were homogeneous with rms roughnesses < 1 nm. 

Aspnes, Theeten, and Hottier made spectroscopic ellipsometry measurements of a surface with induced roughness, and examined calculations with various approximations based on the effective medium model represented by the following relation for the effective dielectric constant < > for a composite layer composed of materials 1 and 2 dispersed in a host medium ... 

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