Protective film thickness measuring method

A protective film thickness measuring method for measuring a thickness of a protective film formed on a top surface of a wafer having patterns on the top surface, the protective film thickness measuring method comprising:

• a pre-protective film formation measuring step of applying light of a first wavelength to the top surface of the wafer in a state in which no protective film is formed and measuring a first reflection intensity of the light reflected from the top surface;
• a protective film forming step of forming the protective film including a light absorbing material on the top surface;
• a post-protective film formation measuring step of irradiating the protective film with exciting light of a second wavelength at which the light absorbing material fluoresces, and measuring a second reflection intensity including fluorescence of the protective film and the light reflected from the top surface by a measuring unit, wherein the second wavelength is different from the first wavelength;
• a protective film fluorescence intensity calculating step of excluding reflection intensity of the patterns formed on the top surface, by subtracting the first reflection intensity measured in the pre-protective film formation measuring step from the second reflection intensity measured in the post-protective film formation measuring step, and calculating fluorescence intensity of the protective film;
• and
• a protective film thickness identifying step of identifying the thickness of the protective film from correlation data regarding correlation between the fluorescence intensity of the protective film and the thickness of the protective film, the correlation data being obtained in advance, and the calculated fluorescence intensity of the protective film.