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 solving both problems in replacing a substrate to be monitored and the task of making film thickness and film quality highly accurately uniform, and controlling the optical film thickness of a multi-layer film of a design wavelength λ0 to an integer multiple of λ0 /4. SOLUTION: A process forms the multi-layer film of the design wavelength λ0 three times or an odd number of times larger than three times the wavelength λV of visible light, by 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 incident onto the substrate 3. Transmitted light is passed through an optical fiber 9 to enter a visible light spectroscope 10. Through the use of an extremal value of a spectroscopic spectrum in the wavelength range of the visible light not including a wavelength λV by the spectroscope 10 and a computing unit 11, it is determined 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.