Interferometric Thickness Measurement of Very Thin Air Gaps or Films
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
Air gaps (or films) in the submicron range are measured by white light interferometry in an optical set-up, using an intermediate optical layer on one of the boundary planes, in order to obtain well-developed interference fringes. Very narrow air gaps, of the order of the wavelength of visible light, are difficult to measure interferometrically, as complete interference fringes (extrema) do not develop; this problem occurs, for example, during the analysis of modern magnetic disks, whose recording heads have a flight height of several hundred nanometers. The flight behavior of these heads is analyzed in a set-up, illustrated in the figure, in which the magnetic disk is simulated by a rotating quartz disk 4. Disk 4 is covered with an intermediate layer 3 which defines an air gap 2 relative to the recording head 1.