PURPOSE: To measure a sulfide residue in a short time with a good sensing accuracy, by removing the natural-oxide film present on either surface or rear surface of a semiconductor wafer therefrom through the dry-etching using a hydrofluoric-acid vapor, and thereafter, by determining the sulfide left on either surface or rear surface of the semiconductor wafer through a Fourier-transform infrared spectroscopy.

CONSTITUTION: A diluted aqueous hydrofluoric-acid solution 1 is filled into a cylindrical Teflon vessel 3 having a somewhat smaller size than a wafer 2, and the vessel 3 is covered with the wafer 2 while its rear surface is turned downward. Then, the natural-oxide film present on the surface or rear surface of the wafer 2 is removed therefrom while it is dry-etched by a hydrofluoric-acid vapor. Thereafter, the sulfide left on either surface or rear surface of the wafer 2 is measured by a Fourier-transform infrared spectroscopy and it is determined. Thereby, the sulfide residue present on the wafer 2 can be measured easily with a good sensing accuracy in a short time on its manufacturing line.