A method and system for spectroscopic ellipsometry employing reflective optics to measure a small region of a sample by reflecting radiation (preferably broadband UV, visible, and near infrared radiation) from the region. The system preferably has an autofocus assembly and a processor programmed to determine from the measurements the thickness and/or complex refractive index of a thin film on the sample. Preferably, only reflective optics are employed along the optical path between the polarizer and analyzer, a sample beam reflects with low incidence angle from each component of the reflective optics, the beam is reflectively focused to a small, compact spot on the sample at a range of high incidence angles, and an incidence angle selection element is provided for selecting for measurement only radiation reflected from the sample at a single, selected angle (or narrow range of angles). The focusing mirror preferably has an elliptical shape to reduce off-axis aberrations in the focused beam. Some embodiments include both a spectrophotometer and an ellipsometer integrated together as a single instrument. In such instrument, the spectrophotometer and ellipsometer share a radiation source, and radiation from the source can be focused by either the spectrophotometer or the ellipsometer to the same focal point on a sample. Preferred embodiments of the ellipsometer employ a rotating, minimal-length Rochon prism as a polarizer, and include a spectrometer with an intensified photodiode array to measure reflected radiation from the sample, and a reference channel (in addition to a sample channel which detects radiation reflected from the sample).

Focused beam spectroscopic ellipsometry method and system

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

Hydrocarbon films were prepared by electron cyclotron resonance plasma deposition from different hydrocarbon source gases at varying ion energies. The source gases used were the saturated hydrocarbons CH4, C2H6, C3H8, C4H10 (n- and iso-) and the unsaturated hydrocarbons C2H4 and C2H2 as well as mixtures of these gases with hydrogen. Film deposition was analyzed in situ by real-time ellipsometry, and the resulting films ex situ by ion-beam analysis. On the basis of the large range of deposition parameters investigated, the correlation between hydrocarbon source gas, deposition parameters, and film properties was determined. The film properties are found to be influenced over a wide range not only by the energy of the impinging ions, but also by the choice of source gas. This is in contrast to a widely accepted study where no dependence of the film properties on the source gas was observed, this being ascribed to a “lost-memory effect.” A strong correlation was found between the hydrogen content of the films and the film properties. This strong correlation is explained on the basis of the random-covalent-network model.

Plasma chemical vapor deposition of hydrocarbon films: The influence of hydrocarbon source gas on the film properties

Phase modulated ellipsometry from the ultraviolet to the infrared: In situ application to the growth of semiconductors

The simultaneous interaction of methyl radicals (CH3) and atomic hydrogen (H) with the surface of amorphous hydrogenated carbon (a-C:H) film is investigated. Two identical quantified beam sources for H and CH3 are used. The growth and/or erosion during the simultaneous interaction of the two beams with an amorphous hydrogenated carbon film is monitored by using in situ real-time ellipsometry at a substrate temperature of 320 K. Interaction with the CH3 beam alone causes slow growth, corresponding to a sticking coefficient for CH3 of ∼3×10−5. Simultaneous interaction of the atomic hydrogen beam and the CH3 radical beam yields a sticking coefficient for CH3 of 3×10−3, which is two orders of magnitude larger than for CH3 alone. From a microscopic modeling of this synergistic growth, the reaction probability for CH3 adsorbing at an adsorption site, which is created by atomic hydrogen at the surface, is derived to be 0.14.

Direct Identification of the Synergism between Methyl Radicals and Atomic Hydrogen during Growth of Amorphous Hydrogenated Carbon Films

The prototype of an infrared spectroscopic ellipsometer using a Fourier transform PC‐based infrared spectrometer is described. Several applications in thin‐film characterization are given, particularly in the case of bulk substrate, thick‐layered materials, and determination of the dielectric function of layered materials such as silicon oxide and silicon nitride. The sensitivity and possible improvements of this technique are discussed.

F. Ferrieu

Papers

Infrared spectroscopic ellipsometry using a Fourier transform infrared spectrometer: some applications in thin-film characterization