Abstract: A substrate having flatness of less than 230 nmPV and surface roughness at RMS of less than 0.20 nm. is obtained by a method comprising: a process of polishing an object to be polished with a polishing pad comprising at least one layer having compressibility of 5% or below in a base layer of the polishing pad.

Abstract: A coefficient of linear expansion measuring apparatus includes: two reflection plates between which a sample is put, a container to house them, which is filled with a gas having known rate of a refractive index variation, a temperature regulating member to set a temperature in the container variably, a light source to irradiate an irradiating light to reflecting surfaces of the reflection plates, a light receiving element to receive reflected lights in which the lights interferes each other and detecting a light intensity thereof, and a calculating member to calculate a coefficient of linear expansion of the sample, wherein: the calculating member calculates an optical path length variation between the reflecting surfaces from an output variation of the light receiving element, and calculates a length variation of the sample by correcting a part of the optical path length variation derived from the refractive index variation of the gas caused by the temperature variation.

Abstract: A substrate having flatness of less than 230 nmPV and surface roughness at RMS of less than 0.20 nm. is obtained by a method comprising: a process of polishing an object to be polished with a polishing pad comprising at least one layer having compressibility of 5% or below in a base layer of the polishing pad.

Abstract: A coefficient of linear expansion measuring apparatus includes: two reflection plates between which a sample is put, a container to house them, which is filled with a gas having known rate of a refractive index variation, a temperature regulating member to set a temperature in the container variably, a light source to irradiate an irradiating light to reflecting surfaces of the reflection plates, a light receiving element to receive reflected lights in which the lights interferes each other and detecting a light intensity thereof, and a calculating member to calculate a coefficient of linear expansion of the sample, wherein: the calculating member calculates an optical path length variation between the reflecting surfaces from an output variation of the light receiving element, and calculates a length variation of the sample by correcting a part of the optical path length variation derived from the refractive index variation of the gas caused by the temperature variation.