No abstract

A graphical method has been developed to determine the plane of incidence in the presence of cell windows with small retardation. For two types of rotating-analyzer ellipsometers, expressions have been derived that relate the experimental parameters and the elements of the Mueller imperfection matrices of the windows. These matrices can be determined by measuring with and without cell windows. Measurements have been performed with three samples with different optical constants.

A fast spectroscopic rotating-polarizer ellipsometer has been developed. The machine is equipped with a cascade arc as a light source, a 1024 element linear photodiode array for parallel data processing, and a fast data acquisition interface that allows for hardware averaging of the data prior to transmission to the controlling computer. The ellipsometer has been mounted on an ultrahigh vacuum chamber. As an example the sublimation of an As cap layer from ErAs/GaAs(100) was studied in situ. Fourier spectra in the range from 1.5 to 4.0 eV with an accuracy and precision better than 2×10−2 and 3×10−4, respectively, are obtained within 1.7 s. The spectral response of the photodiode array is presently the factor limiting the energy range.

Some practical physics-based formulas have been derived to make quick estimates of imaging performances in lithographic systems. These formulas have a simple structure so that they can be used in mathematical worksheets or, if desired, on a pocket calculator. Formulas have been derived to predict the printing of dense lines, bright field isolated lines, and dark field isolated spaces in positive resist. They are for exposures from binary masks and give exposure latitude, focus depth, and change in critical dimension. These parameters are also derived as a function of fading of the aerial images in lateral and focal directions. Validity has been checked with simulations. It proved that, in cases of the aerial image fading and of focus depth evaluation, only a few adjustment parameters were needed to obtain a reasonably good match with simulations. A table with all basic imaging parameters and their dependence on disturbances such as fading is included.