Ellipsometry is a method to measure refractive index: n, extinction coefficient: k, and thickness of surface layers of materials by measuring changes of polarization of reflected light at the surfaces. Generally, n and k change with the wavelength of light. The way of the change is dependent on the microscopic structures of the materials. Therefore, by continuous change of wavelength of the prove, light spectroscopic ellipsometry provides much more information on the materials than the ellipsometry with a fixed wavelength. If the results are combined with the analysis of optical models of material structures, it can fulfill its functions to more extent. The recent rapid development of abilities of small size computers, together with the development of optical elements and systems, has allowed these analyses to be much more time-saving and hence realistic. Recent information about typical spectroscopic ellipsometry is outlined and referred to its instrumentation and the data analyses procedures.
Several analytical, semiempirical models are presented for the complex dielectric function, ε(E)=ε1(E)+iε2(E), of crystalline semiconductors. The harmonic oscillator approximation (HOA) model successfully explains the peculiar experimental a spectra; however, the model cannot be expected a priori to provide satisfactory fits to the dependence of e on external perturbations or to the line shape of the derivatives of ε. The standard critical point (SCP) model provides satisfactory fits to the derivatives of ε, but does not yield good fits to ε. The model dielectric function (MDF), on the other hand, results in excellent agreement with experimental data both for a and its derivatives. The MDF is, thus, con-cluded to be more useful than the HOA or SCP model.
An empirical dielectric function (EDF) and a fluctuated thickness model (FTM) for SE analysis are proposed. EDF satisfies the Kramers-Kronig relations and is applicable to various amorphous materials in the wide spectral range. Several dielectric functions proposed so far are compared together with EDF by applying them to the established table values of of a-Si and a-Si3N4. EDF is used to characterize Si rich nitride (SiRN) films for deep UV lithography as an example. FTM is applied to the characterization of SIMOX (Separation by Implanted Oxygen) with nm thick top Si layer and is found to be much better than introducing an interface roughness layer whose dielectric constants are expressed by an effective medium approximation (EMA). By introducing FTM to the analysis of SIMOX, thickness dependence of dielectric constants in the top Si layers thinner than 5 nm has become able to be detected.
Ellipsometry is an extremely high sensitive method for the film thickness determination. The complex amplitude reflection ratio of the sample is a basic formula for the analysis of the optical constants. The analytical methods of the complex amplitude reflection ratio are described for the both samples of single layer and multilayers. The calculation method for the simultaneous determination of the refractive index and the thickness of a single transparent film is described. We also describe the analytical method for the single absorbing layer of different film thickness. The algorithm for the calculation of the complex amplitude reflection coefficient of the multilayer samples is shown. The effective medium approximation theories of Maxwell-Garnett and Bruggeman are derived starting from the Clausius-Mosotti formula.
With the complexity of recent semiconductor device structures, in-situ monitoring and control for semiconductor processing have become prerequisite to do research and develop the semiconductor devices. Spectroscopic ellipsometry(SE) is an inherently sensitive technique due to the measurement of complex reflection ratios as a function of wavelength. Recent development of high-performance SE setups has enabled the non-contact measurement of thicknesses and compositions for multilayer structures, real-time data acquisition and analysis of the processing and the understanding of monolayer-level surface processes.
Quasi-classical trajectory calculations have been performed on the Eley-Rideal reaction of gas phase H atom with H atom adsorbed on Cu. Vibrational state defined reaction probability has been calculated. A coupling of H2 molecular vibration with a vibrational mode of an adsorbed H atom is considered to be stronger than that with an incident translational mode.
Charge distribution on the surface of 2 : 1 type clay mineral is evaluated by using semi-empirical molecular orbital calculation. The negative charge of clay mineral, which is introduced by isomorphous substitution in tetrahedral and octahedral sheets, is not localized on the oxygen atoms of the surface. We may be able to understand the mechanism of the cation exchange capacity on the clay surface by considering the frontier electron density.
Application of recently developed solid-state NMR techniques to microporous materials such as zeolites and AlPO4 has been introduced. The connectivity of X-Y spin pairs can be examined by dipolar dephasing difference (or TRAP-DOR), cross polarization (CP), REDOR and TEDOR experiments. Those techniques are applied to study the connectivity of Al-O-P and Al-O-Si in the framework structure. They are also applied to study the surface property in terms of the interaction between the surface and adsorbed molecules containing N and P. High resolution solid-state NMR spectra of half-integer quadrupole nuclei such as 27Al and 23Na can be obtained by two-dimensional multiple-quantum spectra under MAS, which has been applied to study Al sites in AlPO4.
Resonant photoemission is a valence band photoemission process following the excitation of inner shell electron to a particular unoccupied state. This reveals information on both occupied and unoccupied states involved in the decay process, and correlation between the two. Although resonant photoemission in metals and their compounds have been studied quite extensively, few studies have been done for organic polymers. In this paper, resonant photoemission in poly (α-methylstyrene) is described, as an example of the results for organic polymers, as well as reviewing earlier works. The results showed that the resonant enhancement is clearly observed for the decay following the excitation to the lowest π* band. Especially, the photoemission from the highest occupied band is largely enhanced. In addition, the energy shift of a valence peak was observed, suggesting the very fast relaxation within the lowest π* band, which is peculiar to solids.
The additive property on quantum mechanical systems is difficult to be approved in principle of quantum mechanics. However the approximate theory based on additive property is farseeing and gives a simple and conceptual model. Can such an approximate theory be acceptable with less approving proof? The consideration about this question is offered in this paper with a discussion of electronegativity concept. The relation to the problem of nonlocal long range correlation of wavefunction is also mentioned.