Lithographic Contaminant Detection via Spatial Intensity Modulation

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Solution Overview

Problem

Lithographic systems face challenges in detecting contaminants on optically critical components, which can introduce errors in pattern transfer due to dynamic processes and contamination buildup, necessitating improved inspection techniques.

Innovation Solution

A system comprising an illumination system with a radiation source and spatial light modulator to adjust the spatial intensity distribution, a detector to receive scattered radiation, and a processor to distinguish between spurious signals and foreign particles based on the adjusted intensity distribution, enhancing the detection of contaminants on reticles and substrates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional inspection techniques are used to detect contaminants on optically critical components, then the detection process is simple, but false positives occur due to spurious signals from scattered radiation

Engineering Contradiction:

Improvecontaminant detection accuracyVSAvoidfalse positive rate

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The inspection process is divided into multiple sequential stages: initial contaminant detection, spurious signal identification through scattered radiation analysis, and final verification. This segmentation allows the system to differentiate between genuine contaminants and false signals by analyzing radiation scattering patterns at different inspection phases

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The system introduces an intermediary analysis layer that examines scattered radiation patterns between the radiation source and the detector. This intermediary step identifies spurious signals by detecting characteristic scattering patterns, preventing them from being misidentified as genuine contaminants while allowing true contaminants to be detected

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If dynamic processes occur in the lithographic apparatus, then the system remains operational and productive, but contaminant particles are introduced and built up over time

Engineering Contradiction:

Improvelithographic operation continuityVSAvoidcontaminant buildup

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The inspection system performs preliminary contaminant detection before contaminants can interfere with pattern transfer. By continuously monitoring optically critical components during and between lithographic operations, the system identifies contaminants early in their development, allowing for preventive maintenance before productivity is impacted

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system establishes a feedback loop where inspection results are fed back into the operational schedule. When contaminants are detected on optically critical components, the system provides feedback to pause operations or trigger cleaning protocols, preventing contaminant buildup from reaching levels that would compromise pattern transfer quality

Inventive Principle:

Principle #23Feedback

3Manufacturing precision

If sub-nanometer tolerances are maintained for pattern transfer, then pattern accuracy is improved, but contaminant detection becomes more critical and difficult

Engineering Contradiction:

Improvepattern transfer accuracyVSAvoidcontaminant detection complexity

Core Design Contradiction:

Manufacturing precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The inspection system applies local quality analysis by examining specific regions of optically critical components with heightened sensitivity. Rather than uniform inspection, the system focuses detection resources on areas most critical for sub-nanometer pattern transfer, using localized scattering pattern analysis to detect contaminants that would affect precision patterning

Inventive Principle:

Principle #3Local quality

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 solution effectively reduces false positives and improves the accuracy of contaminant detection, ensuring sub-nanometer precision in pattern transfer by differentiating between genuine contaminants and spurious signals, thereby maintaining the integrity of lithographic processes.

Implementation Method 1

The detector is configured to receive radiation scattered at the surface and by a structure near the surface

Methodology Applied

Scientific EffectLight scattering: Scattering

Data Source

PatentUS11803119B2Contaminant detection metrology system, lithographic apparatus, and methods thereof

Publication Date: 2023.10.31 ASML NETHERLANDS BV

AI summary

A system (400) includes an illumination system (402), a detector (404), and a comparator (406). The illumination system includes a radiation source (408) and a spatial light modulator (410). The radiation source generates a beam of radiation (442). The spatial light modulator directs the beam toward a surface (436) of an object (428) and adjusts a spatial intensity distribution of the beam at the surface. The detector receives radiation (444) scattered at the surface and by a structure (434) near the surface. The detector generates a detection signal based on the received radiation. The comparator receives the detection signal, generates a first image based on the detection signal, and distinguishes between a spurious signal and a signal corresponding to a presence of a foreign particle on the surface based on the first image and the adjusted spatial intensity distribution.