Systems and methods for generating multiple illumination spots from a single illumination source

Abstract

Spots of illumination directed at a target are described. Ghost reflections often prevalent in wafer alignment sensors are reduced or eliminated. First, second, and third optical elements are described. The first optical element receives illumination along a first axis, reflects a first portion of the illumination away from the first axis, and transmits a second portion of the illumination along the first axis. The second first optical element receives the first portion of the reflected illumination and at least partially reflects a third portion of the illumination along a second axis. The third first optical element receives and fully reflects a fourth portion of the illumination along a third axis. The second portion, third and fourth portions of the illumination are directed toward the target at different angles relative to each other to create three different spots of illumination.

Dependencies are inferred from the claim text.