EUV Lithography Field Mirror Corrective Positioning

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Solution Overview

Problem

Lithographic apparatuses using EUV radiation face challenges with movable facet mirrors that can become stuck, leading to imaging errors and defective devices due to telecentricity errors, as transmissive optical elements are not suitable for EUV and traditional facet mirrors are prone to mechanical failures.

Innovation Solution

A lithographic apparatus with a field facet mirror system comprising movable reflective elements that can be set to corrective positions to mitigate the effects of defective facets, ensuring a resilient illumination system by adjusting other facets to maintain desired illumination modes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional facet mirrors are used in EUV lithography, then the illumination system can be constructed, but mechanical failures occur causing telecentricity errors and imaging defects

Engineering Contradiction:

Improvereliability of movable facet mirrorsVSAvoidimaging errors and telecentricity errors

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The control system proactively detects when a facet mirror is stuck in its current position and preemptively compensates by adjusting other facet mirrors before imaging errors occur. This preliminary compensation action prevents telecentricity errors and maintains illumination mode integrity without requiring mechanical repair of the defective mirror.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors the positions of all facet mirrors and implements a feedback loop where the control system detects stuck mirrors and automatically adjusts other mirrors to compensate. This closed-loop feedback mechanism ensures that illumination quality is maintained despite mechanical failures in individual mirror elements.

Inventive Principle:

Principle #23Feedback

2Manufacturing precision

If a facet mirror is stuck in a non-desired position, then the illumination mode is compromised, but corrective positioning of other facets can restore imaging quality

Engineering Contradiction:

Improveimaging qualityVSAvoidcomplexity of control system

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The control system implements continuous monitoring of facet mirror positions and automatically detects when mirrors are stuck. It then calculates and applies corrective positioning to other mirrors to compensate for the defect, maintaining imaging quality through this closed-loop feedback mechanism.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes the positioning parameters of healthy facet mirrors to compensate for the stuck mirror. By adjusting the angular positions and orientations of other facets, the control system alters the illumination path to bypass the defective element and restore the desired illumination mode at the pupil plane.

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If movable facet mirrors are used to define illumination modes, then illumination flexibility is improved, but mechanical failures cause telecentricity errors

Engineering Contradiction:

Improveillumination mode flexibilityVSAvoidreliability of movable components

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The control system proactively detects stuck facet mirrors and preemptively compensates by repositioning other mirrors before imaging errors occur. This preliminary action maintains illumination mode flexibility while preventing reliability issues from manifesting as imaging defects.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system prepares compensation strategies in advance by monitoring the operational status of all facet mirrors. When a mirror is detected as stuck, pre-calculated corrective positions for other mirrors are applied, cushioning against the potential harm of mechanical failure and maintaining system reliability.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 enhances the resilience of the lithographic apparatus to defective facets, reducing imaging errors and maintaining imaging quality by allowing for corrective adjustments in the illumination system, thereby improving the production of high-quality devices.

Implementation Method 1

a first reflective component and a second reflective component, the first reflective component being arranged to direct radiation of the radiation beam onto the second reflective component

Methodology Applied

Scientific EffectReflection: Reflection

Implementation Method 2

each movable reflective element being movable between at least a first position and a second position so as to change an illumination mode

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS9170500B2Lithographic apparatus and device manufacturing method with corrective positioning of reflective element

Publication Date: 2015.10.27 ASML NETHERLANDS BV

AI summary

In a lithographic apparatus, an illumination mode is set using a field mirror comprising a plurality of movable facets to direct radiation to selectable positions on a pupil facet mirror. In the event that a field facet mirror is defective and cannot be set to a desired position, another of the movable facet mirrors is set to a corrective position, different than its desired position, to at least partially ameliorate a deleterious effect of the defective facet mirror.