Polarization independent metrology system

Abstract

A metrology system includes a radiation source that generates light, an optical modulation unit, a reflector, an interferometer, and a detector. The optical modulating unit temporally separates a first polarization mode of the light from a second polarization mode of the light. The reflector directs the light towards a substrate. The interferometer interferes the diffracted light from a pattern onthe substrate, or reflected light from the substrate, and produces output light from the interference. The detector receives the output light from the interferometer. The first and second polarization modes of the output light are temporally separated at the detector.

Description

[0001] Cross References to Related Applications [0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 247,116, filed October 27, 2015, and is incorporated herein by reference in its entirety. technical field [0003] The present disclosure relates to metrology systems that may be used, for example, in lithographic apparatus. Background technique [0004] A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. A lithographic apparatus may be used, for example, in the manufacture of integrated circuits (ICs). In this case, a patterning device, alternatively called a mask or reticle, can be used to create a circuit pattern corresponding to a single layer of the IC, and this pattern can be imaged onto a layer of radiation-sensitive material (resist). layer on a target portion (eg, a portion including a die, one or more dies) on a substrate (eg, a silicon wafer). Typically, a single substrate ...

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Problems solved by technology

Such an implementation is costly and difficult to perform the alignment of the axes of the two interferometers

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