In a typical reflection ellipsometry experiment, one characterizes the polarization state change that a polarized light beam undergoes upon reflection from a specular surface. This measurement provides ρ≡rp/rs, where rp and rs are the complex amplitude reflection coefficients of the surface for p‐ and s‐polarized waves. Nearly 15 years have passed since the development of automatic ellipsometers along with the detailed calibration, error analysis, and data reduction procedures to be used with them. More specifically, these powerful instruments permit (1) determination of bulk dielectric functions and nondestructive depth profiling of static multilayered materials through measurements as a function of photon energy and (2) characterization of dynamic surfaces in adverse environments through measurements as a function of time at fixed photon energy. In the 15 intervening years, the major research thrusts in ellipsometry have been the exploitation of these instruments in materials and process characterizatio...

Automatic rotating element ellipsometers: Calibration, operation, and real‐time applications

A new type of spectroscopic automatic ellipsometer using a piezobirefringent element for polarization modulation at 50 kHz is described. Instead of lock‐in amplifiers the data‐acquisition system consists of a 12.8‐MHz digital sampling of the detected signal with a high word rate 8‐bit ADC, followed by on line Fourier transformation of the accumulated data with a short instruction cycle (∼200 ns) microprocessor, driven by a commercial microcomputer. The absolute minimum time required for measuring one set of Fourier coefficients is thus reduced to the modulation period of 20 μs. For digital error reduction purposes and signal‐to‐noise ratio improvement a basic 5 ms sequence of 256 accumulated periods per point is chosen. At this data‐acquisition rate a precision of 5×10−4 is obtained. Further accumulation over 10 s leads to 10−5 precision capability. A detailed analysis of various sources of inaccuracy leads to an estimate of 0.5° maximum systematic error on the ellipsometric angles and ψ and Δ. Applicatio...

Fast polarization modulated ellipsometer using a microprocessor system for digital Fourier analysis

Self-assembled monolayers (SAMs) of octyltrimethoxysilane (OTMS) were deposited onto indium−tin oxide (ITO) electrode surfaces. Contact angle measurements evidenced the hydrophobicity and homogeneity of the functionalized surface despite the intrinsic surface roughness of the polycrystalline ITO electrodes. The electrochemical properties of the OTMS monolayers were quantitatively analyzed in terms of resistance, dielectric thickness, diffusion constant, and defect area by cyclic voltammetry and impedance spectroscopy. It has been demonstrated that the alkylsiloxane monolayer acts as a diffusion barrier for ions in the electrolyte. Furthermore, a significant suppression of the charge transfer at the interface was observed, demonstrating the passivation effect of the monolayers against electrochemistry. In addition, the effect of alkyl chain length on the electrochemical properties was briefly analyzed by using octadecyltrimethoxysilane (ODTMS). The defect area of this self-assembled monolayer was reduced t...

Electrochemical Characterization of Self-Assembled Alkylsiloxane Monolayers on Indium−Tin Oxide (ITO) Semiconductor Electrodes

The plasma growth rate of native layers, such as oxide and nitride, on silicon is enhanced by the addition of fluorine. An increase in growth rate is obtained, and the oxide growth rates on doped and undoped portions of the silicon substrate are substantially the same. The fluorine is typically added by means of a fluorinated compound, typically CF4, comprising 0.01 to 5 molecular percent of the plasma. Lower substrate temperatures, typically less than 600 degrees C., may be used, resulting in less warpage of the wafer and less diffusion of dopants.

Fluorine enhanced plasma growth of native layers on silicon

Publisher Summary Electromagnetic theory aids in understanding the different techniques used to determine optical properties of materials. It is noted that if the electromagnetic wave is reflected by a smooth surface, the outgoing wave can be represented in the absence of anisotropic effects in another local coordinate system. Wherein, both the local coordinate systems the x axes are in the plane of incidence, the y axis is perpendicular to the plane of incidence, and the z axes define the plane of incidence. Four parameters—namely, two amplitudes and two phases are necessary to completely describe the incoming wave to describe the sample. The properties of the sample therefore are obtainable, if the properties of both incident and reflected waves are known. Reflectometry and ellipsometry are essentially two techniques for obtaining this information. For isotropic samples ellipsometry is strictly a nonnormal-incidence technique, while reflectometry and polarimetry can be performed at either normal or nonnormal incidence. Reflectometry deals with intensities and is therefore a power measurement, while ellipsometry deals with intensity-independent complex quantities and is therefore more nearly analogous to an impedance measurement.

T. E. Adams

Papers

In Situ Measurement and Analysis of Plasma‐Grown GaAs Oxides with Spectroscopic Ellipsometry