Abstract: The present invention relates to a method of cleaning an optical film-thickness measuring system used for measuring a film thickness of a substrate, such as a wafer, while polishing the substrate. The method includes: cleaning an optical sensor head (7) by supplying a rinsing liquid into a through-hole (51) formed in a polishing pad (2) on a polishing table (3) before or after polishing of a substrate (W) with use of slurry, the optical sensor head (7) being located below the through-hole (51); and discharging the rinsing liquid from the through-hole (51) through a drain line (54).

Abstract: An emulsion composition according to the present invention includes: a polymerizable compound comprising two or more (meth)acryloyl groups; a surfactant; and a dispersion medium including water as a principal component, in which an oil droplet diameter D90 corresponding to a diameter at cumulative 90% by volume in the oil droplet size distribution of oil droplets comprising the polymerizable compound and the surfactant, measured according to a laser diffraction and scattering measurement process is less than 1.8 ?m. A maximum oil droplet diameter Dmax of the oil droplets, measured according to the laser diffraction and scattering measurement process is preferably less than 4.0 ?m. A content of the polymerizable compound in the composition with respect to 100 parts by mass of a total of components other than the dispersion medium is preferably no less than 40 parts by mass. The oil droplets may further comprise an inorganic particle.

Abstract: An emulsion composition according to the present invention includes: a polymerizable compound comprising two or more (meth)acryloyl groups; a surfactant; and a dispersion medium including water as a principal component, in which an oil droplet diameter D90 corresponding to a diameter at cumulative 90% by volume in the oil droplet size distribution of oil droplets comprising the polymerizable compound and the surfactant, measured according to a laser diffraction and scattering measurement process is less than 1.8 ?m. A maximum oil droplet diameter Dmax of the oil droplets, measured according to the laser diffraction and scattering measurement process is preferably less than 4.0 ?m. A content of the polymerizable compound in the composition with respect to 100 parts by mass of a total of components other than the dispersion medium is preferably no less than 40 parts by mass. The oil droplets may further comprise an inorganic particle.