Wavelength Selection Module with Linear Variable Filters for Fast Switching

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Solution Overview

Problem

Current metrology apparatuses in lithographic processes face limitations in switching speed between discrete wavelengths, which hampers measurement throughput due to the need for time-consuming adjustments.

Innovation Solution

Implement a wavelength selection module with at least two linear variable filters (LVFs) to control the wavelength characteristic of the output radiation beam, allowing for faster and more flexible wavelength selection by reducing the number of large rotations required.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If discrete wavelength filters are used in metrology apparatuses, then wavelength selection capability is provided, but switching speed between wavelengths is slow

Engineering Contradiction:

Improvewavelength switching speedVSAvoidtime for wavelength adjustments

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The wavelength range is segmented into multiple overlapping bands, with each linear variable filter element responsible for a specific segment. This allows the system to switch between wavelengths within the same segment instantly without requiring large rotations, thereby improving switching speed while maintaining comprehensive wavelength coverage through overlapping segments

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs linear variable filters that can be dynamically adjusted by rotating filter elements. The overlapping wavelength bands allow for dynamic switching between adjacent bands with minimal rotation, enabling fast and flexible wavelength selection. The system transitions from static discrete filters to dynamically adjustable continuous variable filters, resolving the contradiction between wavelength selection capability and switching speed

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If multiple discrete wavelength filters are used, then comprehensive wavelength coverage is achieved, but device complexity increases

Engineering Contradiction:

Improvewavelength coverage rangeVSAvoidnumber of filter elements

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent merges multiple discrete filter functions into continuous linear variable filters. Instead of using separate physical filters for each wavelength band, the system combines overlapping wavelength ranges into single variable filter elements that can continuously adjust their transmission characteristics, thereby reducing the total number of filter elements while maintaining comprehensive wavelength coverage

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

Each linear variable filter element is designed to handle multiple wavelength bands simultaneously through overlapping transmission ranges. A single filter element can serve multiple functions by adjusting its orientation, replacing what would traditionally require multiple discrete filters. This multi-functionality reduces device complexity while preserving adaptability across the full wavelength spectrum

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 throughput by significantly reducing the time needed for wavelength switching, improving the efficiency of metrology apparatuses in lithographic processes.

Implementation Method 1

at least one of said one or more filter elements comprises at least two linear variable filters

Methodology Applied

Scientific EffectLinear variable filter: Filter (optical)

Data Source

PatentUS12460971B2Wavelength selection module, illumination system and metrology system

Publication Date: 2025.11.04 ASML NETHERLANDS BV

AI summary

Disclosed is a wavelength selection module for a metrology apparatus. The wavelength selection module comprises one or more filter elements being operable to receive an input radiation beam comprising multiple wavelengths to provide selective control of a wavelength characteristic of a corresponding output radiation beam. At least one of said one or more filter elements comprises at least two linear variable filters.