Inspection tool for an extreme ultraviolet radiation source to observe tin residual

Abstract

A method of inspecting an extreme ultraviolet (EUV) radiation source includes, in an idle mode, inserting a borescope mounted on a fixture through a first opening into a chamber of the EUV radiation source. The borescope includes a connection cable attached at a first end to a camera. The EUV radiation source includes an excitation laser that generates a light beam that is configured to focus onto tin droplets to generate EUV radiation inside the chamber of the EUV radiation source. The method further includes extending the extendible section, in a direction toward the second opening of the EUV radiation source, to move the camera beyond the blocking shield, and acquiring one or more images from a region beyond the blocking shield. The method also includes analyzing the one or more acquired images to determine an amount of tin debris deposited inside the chamber of the EUV radiation source.