Self-referencing interferometer, alignment system, and lithographic apparatus

Abstract

The invention discloses a self-reference interferometer, an alignment system and photolithography equipment. A self-referencing interferometer includes optics to split the alignment beam to produce a reference beam and a transformed beam. The optical system includes a beam splitter to combine the reference and transformed beams such that diffraction orders in the reference beam spatially overlap with their respective opposite diffraction orders in the transformed beam. A detector system receives the spatially overlapping reference and transformed beams from the optical system and determines a position signal. The detector system includes a polarization system for manipulating the polarization of the beams such that they interfere, and for directing the interfering reference beams and transforming the beams to the detection for determining the position signal from the intensity variation of the interfering beams device.

Description

technical field [0001] The invention relates to a self-referencing interferometer, an alignment system provided with a self-referencing interferometer and a lithographic apparatus provided with such an alignment system. Background technique [0002] A lithographic apparatus is a machine that applies a desired pattern to a substrate, usually to a target portion of the substrate. For example, lithographic equipment may be used in the manufacture of integrated circuits (ICs). In this case, a patterning device, alternatively referred to as a mask or reticle, may be used to generate the circuit pattern to be formed on the individual layers of the IC. The pattern can be transferred onto a target portion (eg, comprising a portion, one or more dies) on a substrate (eg, a silicon wafer). Typically, the pattern is transferred via imaging to a layer of radiation sensitive material (resist) provided on the substrate. Typically, a single substrate will contain a network of successivel...

AI Technical Summary

Problems solved by technology

[0005] A drawback of known alignment systems is that self-referencing interferometers in alignment measurement systems can be relatively expensive due to their optical design requiring the use of specially manufactured optical components

Another disadvantage of known alignment systems is that known self-referencing interferometers are usually rather bulky

This bulkiness can lead to undesired side effects in the alignment process (such as low bandwidth vibration modes), which can reduce the accuracy of the alignment process

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