Optical inspection device and its control method

Abstract

An optical inspection apparatus and its control method are provided, which can accurately determine the film thickness of a film covering a sample even when there is a difference in the spatial intensity distribution between the light irradiating the sample and the light irradiating a reference mirror. An optical inspection apparatus includes: a light source for emitting light; a beam splitter for splitting the light emitted from the light source into a first irradiation light directed toward a sample and a second irradiation light directed toward a reference mirror; an interference light measurement unit for measuring the interference light caused by the reflection of the first irradiation light on the sample (i.e., object light) and the reflection of the second irradiation light on the reference mirror (i.e., reference light); and a control unit for controlling each unit. The optical inspection apparatus is characterized by further including: an object light measurement unit for measuring only the intensity of the object light; and a memory unit for storing the intensity of the object light on a reference sample previously measured by the object light measurement unit; the control unit determining the film thickness of a film covering the observation sample based on the intensity of the object light on the reference sample and the intensity of the object light on the observation sample measured by the object light measurement unit.

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