Patent ID: 8339568
Filing Date: 2012-12-25
Classification: G01N,G03B,G03F

Abstract:
1. A foreign particle inspection apparatus including a light projecting unit which projects light to a surface of an object to be inspected, a photo-receiving unit which receives the light that is projected to the surface by the light projecting unit and scattered by the surface, and a controller which determines a size of a foreign particle on the surface based on the output from the photo-receiving unit, wherein the light projecting unit is arranged such that an optical axis of the light projecting unit is tilted with respect to the surface, the photo-receiving unit is arranged such that an optical axis of the photo-receiving unit is tilted by a first angle with respect to a plane including the optical axis of the light projecting unit and a normal axis to the surface, and when an angle of a polarization axis of the projected light with respect to the plane is defined as a second angle, the controller controls at least one of the polarization axis of the projected light and the arrangement of the photo-receiving unit so that differences between the first angle and the second angle become a first state and a second state which are different from each other, and wherein the controller determines the size of the foreign particle based on the output from the photo-receiving unit in the first state and the output from the photo-receiving unit in the second state using a data which represents a relation between the size of a foreign particle and the output from the photo-receiving unit when the photo-receiving unit receives the light from the foreign particle, and wherein the data which represents the relation between the size of a foreign particle and an output from the photo-receiving unit when the photo-receiving unit receives the light from the foreign particle includes a data where the relation between the size of the foreign particle and the output from the photo-receiving unit when the photo-receiving unit receives the light from the foreign particle is linear, when the difference between the first angle and the second angle is in the second state, in a range of the size of the foreign particle where the relation between the size of the foreign particle and the output from the photo-receiving unit when the photo-receiving unit receives the light from the foreign particle is not linear when the difference between the first angle and the second angle is in the first state.