Measurement of the Thickness of Thin Films by Multiple Beam Interferometry

摘要

A Multiple-Beam Interferometer was developed for the measurement of the thickness of vacuum deposited thin films. The thicknesses measured were in the region of 1000 to 10,000 Angstroms. Both Monochromatic Fizeau fringes of equal thickness and heterochromatic fringes of equal chromatic order were investigated, but the latter method was chosen for the actual measurements because of its greater accuracy and less stringent experimental requirements. Five SiO films and one Cr film were measured. Two of the SiO films were deposited simultaneously and the measured thicknesses of these were used to evaluate the uniformity of the deposition. The fringes of equal chromatic order were also used to investigate the reflection phase dispersion by the Al overcoats on the SiO films and by the Cr overcoat on the Cr film. The functional form of this phase dispersion determines whether or not a simple formula for the thickness computation is valid. (Author)