Line-Narrowing Laser Wavelength Control With Notch Filtering

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Solution Overview

Problem

Existing line narrowing laser devices face challenges in accurately controlling the periodic change of target wavelengths due to operational limitations of rotation stages, leading to inaccuracies in wavelength control and potential chromatic aberration issues in semiconductor exposure systems.

Innovation Solution

Incorporating a notch filter in the wavelength control signal path, specifically a fixed or variable notch filter with bandpass filters, to attenuate frequency components at specific frequencies, allowing for precise control of wavelength changes and reducing deviations between target and measurement wavelengths.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a line narrowing module is provided in the laser resonator to narrow the spectral line width, then chromatic aberration is reduced, but the wavelength cannot be periodically changed for resolution improvement

Engineering Contradiction:

Improvechromatic aberrationVSAvoidwavelength change capability

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies the dynamics principle by making the optical element (mirror or prism) movable through a wavelength actuator. This allows the incident angle of light on the diffractive optical element to be dynamically adjusted, enabling periodic wavelength changes while maintaining line narrowing functionality. The movable optical element resolves the contradiction by providing both spectral line width control and wavelength adaptability.

Inventive Principle:

Principle #15Dynamics

2Manufacturing precision

If the wavelength is periodically changed to improve resolution, then manufacturing precision improves, but control inaccuracies and chromatic aberration may occur

Engineering Contradiction:

ImproveresolutionVSAvoidwavelength control accuracy

Core Design Contradiction:

Manufacturing precisionVSMeasurement precision

Solution Approach 1:

The patent implements feedback control by using a wavelength monitor to detect the actual wavelength and a control unit to adjust the wavelength actuator based on the detected wavelength. This closed-loop feedback system ensures accurate wavelength control during periodic changes, resolving the contradiction between achieving resolution improvement through wavelength modulation and maintaining wavelength control accuracy.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If a rotation stage is used to change the incident angle, then wavelength control is possible, but operational limitations reduce control accuracy

Engineering Contradiction:

Improvewavelength controlVSAvoidcontrol accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent replaces the traditional rotation stage mechanical system with a wavelength actuator that directly adjusts the optical element's position or angle. This substitution reduces mechanical operational limitations and improves control accuracy while maintaining the ability to change wavelengths. The actuator provides more precise and reliable wavelength control compared to rotation stage mechanisms.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The notch filter enables accurate periodic wavelength changes, improving the alignment of target and measurement wavelengths, thereby enhancing the resolution and reducing chromatic aberration in semiconductor exposure systems.

Implementation Method 1

a diffractive optical element positioned on an optical path of an optical resonator

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

a notch filter arranged in a path of the wavelength control signal and configured to operate at a notch frequency different from a drive frequency of the wavelength actuator

Methodology Applied

Scientific EffectFrequency filtering: Filter (electronic)

Data Source

PatentUS20240413600A1Line narrowing laser device, and electronic device manufacturing method

Publication Date: 2024.12.12 GIGAPHOTON INC

AI summary

A line narrowing laser device includes an optical element and a diffractive optical element positioned on an optical path of an optical resonator, a wavelength actuator configured to change an incident angle of light incident on the diffractive optical element by moving the optical element, a wavelength driver configured to drive the wavelength actuator, a processor configured to output a wavelength control signal to the wavelength driver so that a wavelength of pulse laser light output from the optical resonator periodically changes, and a notch filter arranged in a path of the wavelength control signal and configured to operate at a notch frequency different from a drive frequency of the wavelength actuator.