FILM THICKNESS MONITORING APPARATUS AND METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a film thickness monitoring apparatus and a method capable of highly efficiently producing a multi-layer film in which the number of layers is large and approximately tens to hundreds and of which the optical film thickness is highly accurately controlled to an integer multiple of λ0 /4. SOLUTION: In a process for alternately forming a film of a high refractive index (H film) and a film of a low refractive index (L film) on a substrate 3 in a film forming chamber 2 by sputtering from an ECR sputtering source 4, light from a light source 5 is passed through an optical fiber 6 and made vertically incident onto the substrate 3. Transmitted light is passed through an optical fiber 9 to enter a spectroscope 10, and data on a spectroscopic spectrum outputted from the spectroscope 10 is inputted to a computing unit 11 to acquire an extremal value of the spectroscopic spectrum in a wavelength range not including a wavelength λ0 . It is determined through the use of the extremal value whether the optical film thickness of the H film or the L film during film formation is equal to an integer multiple of λ0 /4 or not in the film thickness monitoring method.