Patent ID: 11965730
Assignee: SHIN-ETSU HANDOTAI CO., LTD.
Field: Measurement (Instruments)
Classification: CPC G  H | IPC G

Claim 0:
1. A method for measuring a film thickness distribution of a wafer with thin films, by which a film thickness distribution of a second thin film of a wafer with thin films is measured, the wafer including at least a first thin film formed on a surface of a substrate and the second thin film formed on a surface of the first thin film, the method comprising the steps of:
determining a height Z1 of a focus using the wafer with thin films and an optical microscope with an autofocus function which uses irradiation light of wavelength λ0 to adjust the focus;
determining a wavelength λ1 of irradiation light used for obtaining an observation image of the second thin film of the wafer with thin films;
obtaining the observation image of the second thin film of the wafer with thin films using the optical microscope with the irradiation light of the wavelength λ1, while altering heights of the focus with the Z1 as a reference point;
calculating a standard deviation of a reflected-light intensity distribution within the observation image, obtaining a height Z2 of the focus corresponding to a peak position where the standard deviation of the reflected-light intensity distribution is greatest, and calculating a difference ΔZ between the Z1 and the Z2;
correcting the autofocus function of the optical microscope with the ΔZ as a correction value; and
using the corrected autofocus function to adjust the focus, obtaining the observation image of the second thin film of the wafer with thin films using the optical microscope, and calculating the film thickness distribution of the second thin film from the reflected-light intensity distribution within the observation image.