Method of and apparatus for inspecting residue of metal film

Abstract

A maximum value of a spectral reflectance at each wavelength with changes in the thickness of a top layer of a multi-layer dielectric film is determined as a maximum reflectance represented by a curve (MLmax) in a graph. In the presence of a residual metal film on the multi-layer dielectric film, the spectral reflectance changes from a curve (A50) to a curve (A5) in the graph with the decrease in the thickness of the residual metal film. In the absence of the residual metal film, the spectral reflectance is represented by a curve (A0) in the graph. Based on the foregoing, a peak wavelength at which the spectral reflectance of a multi-layer film to be judged reaches a peak is determined in a specified wavelength range. When the reflectance of the multi-layer film to be inspected at the peak wavelength is greater than the maximum reflectance, it is concluded that the multi-layer film to be inspected has the residual metal film. When the reflectance of the multi-layer film to be inspected at the peak wavelength is equal to or less than the maximum reflectance, it is concluded that the residual metal film is absent. The presence or absence of the residual metal film on the multi-layer dielectric film is inspected using simple calculation without the need for optical constants of metal.