REAL-TIME SPECTROSCOPIC ELLIPSOMETRY FOR CHARACTERIZATION OF THIN-FILM OPTICAL-PROPERTIES AND MICROSTRUCTURAL EVOLUTION

A rotating polarizer multichannel ellipsometer was applied in spectroscopic (1.3-4.2 eV) investigations of thin films during deposition. In this review, two examples are selected which demonstrate real time spectroscopic ellipsometry. In the first, we compare results for amorphous silicon and germanium sputtered to approximately 50 angstrom on native oxide-covered c-Si. For these films, the evolution of the effective optical properties with thickness is dominated by changes in void volume fraction and surface roughness which accompany nucleation and growth. Abrupt transitions from cluster to bulk film growth occur at total thicknesses of 10-15 angstrom for materials deposited under optimum conditions of microstructural uniformity. In the second example, corresponding results for aluminum evaporated to opacity onto thermally oxidized c-Si are discussed. In this case, the evolution of the effective optical properties with thickness is strongly influenced by changes in the intrinsic aluminum dielectric function. In particular, we find that the relaxation time for the (200) parallel-band transition increases abruptly with thickness over the 55-60 angstrom range. The enhanced scattering of electrons in the films less than 60 angstrom thick may originate from a disordered or fine-grained film structure, and for thicknesses less than 55 angstrom the (200) parallel-band feature in the aluminum dielectric function at 1.5 eV disappears.