A comparison of methods for accurate film thickness measurement

Three methods, two optical and one electromechanical, have been employed for determining film thickness by measuring the step height at the edge of the film. The optical techniques were multiple-beam Fizeau interferometry and photoelectric shearing interferometry while the RPI Talystep, a stylus measuring instrument, provided the third method. The three techniques have the common feature of possessing extremely high sensitivity and their merits and disadvantages are discussed. A comparison of measurements on magnesium fluoride, aluminium and gold films with thicknesses ranging between 100 and 2000 AA is presented and shows that results from the three methods were generally in excellent agreement, the overall spread of values rarely exceeding 10 AA.