Abstract: An apparatus for measuring thickness is provided. A light source irradiates a front surface or a rear surface of a substrate with a light. A splitter splits the light into a reference light and a measurement light. The reference light is reflected by a reference light reflecting device. An optical path changing device changes an optical path length of light reflected from the reference light reflecting device. A light receiving device measures an interference of the reflected light from the substrate and the reference light from the reference light reflecting device. A thickness of at least one of the front surface, rear surface or inside of the substrate is measured based on a measurement of the interference.

Abstract: The temperature of the surface and/or inside of a substrate is measured by irradiating the front surface or rear surface of the substrate, whose temperature is to be measured, with light and measuring the interference of a reflected light from the substrate and a reference light. A method and apparatus for measuring temperature or thickness which is suitable for directly measuring the temperature of the outermost surface layer of a substrate, and an apparatus for treating a substrate for an electronic device, which uses such method, are provided.

Abstract: The temperature of the surface and/or inside of a substrate is measured by irradiating the front surface or rear surface of the substrate, whose temperature is to be measured, with light and measuring the interference of a reflected light from the substrate and a reference light. A method and apparatus for measuring temperature or thickness which is suitable for directly measuring the temperature of the outermost surface layer of a substrate, and an apparatus for treating a substrate for an electronic device, which uses such method, are provided.