Interferometer Jitter Compensation Using Power-Modulated Signals

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Solution Overview

Problem

Jitter caused by components in interferometer systems, such as electronics and optical fibers, limits the measurement accuracy of positioning systems in lithographic apparatuses.

Innovation Solution

An interferometer system that includes a light source emitting two light beams, one traveling along a measurement path with a target and the other along a fixed reference path, with a signal generator introducing a power-modulated optical signal to determine and compensate for jitter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a heterodyne interferometer system is used for positioning, then position information can be obtained, but measurement accuracy is limited by jitter from electronics and optical fibers

Engineering Contradiction:

Improveposition measurement accuracyVSAvoidmeasurement stability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent introduces a power-modulated optical signal at a specific frequency into the measurement or reference path. By detecting this modulated signal after it travels through the interferometer components, the system characterizes and determines the jitter caused by electronics and optical fibers. This converts the harmful jitter effect into a measurable signal characteristic that can be used for compensation, thereby improving measurement accuracy while maintaining system reliability

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system implements a feedback mechanism where the detected power-modulated signal is used to determine jitter characteristics, which then feed back into the measurement process to compensate for jitter-induced errors. This closed-loop approach continuously corrects for instability sources, resolving the contradiction between obtaining position information and maintaining measurement stability

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enhances measurement accuracy by compensating for jitter, allowing precise positioning in lithographic apparatuses.

Implementation Method 1

a light source configured to emit a first light beam and a second light beam

Methodology Applied

Scientific EffectLight emission: Light

Implementation Method 2

both first portions are made to interfere, after which the power of the interference result is detected by a reference detector while a second portion of the first light beam is allowed to travel along a measurement path

Methodology Applied

Scientific EffectOptical interference: Interference

Data Source

PatentUS12481226B2Interferometer system, positioning system, a lithographic apparatus, a jitter determination method, and a device manufacturing method

Publication Date: 2025.11.25 ASML NETHERLANDS BV

AI summary

An interferometer system includes an optics system configured to allow a first light beam to travel along a measurement path including a target, and a second light beam to travel along a fixed reference path excluding the target; and a signal generator configured to introduce a power-modulated optical signal in the measurement path or the reference path to determine jitter caused by components of the interferometer system downstream of the signal generator.