INTERFEROMETRIC DETERMINATION OF THICKNESS OF FREESTANDING SUBMICRON FORMVAR FILMS

A method tor measuring the thickness of free-standing films of Formvar in the range of 2000 angstrom to 5 mum is presented. The optical path difference of the film with reference to air is measured using a modi fied Jamin interferometer, and the refractive index is determined by a thin wedge technique. The method provides thickness measurements with an accuracy of +/-300 angstrom. The results are found to be in good a greement with those obtained from a profilometer. This simple method c an be very useful for thickness measurement of free-standing thin plas tic films for extreme ultraviolet (XUV) soft x-ray research applicatio ns.