Lens Terminating Element Positioning Using Capacitive Sensors

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Solution Overview

Problem

In projection lenses, particularly for microlithography, the exchangeable terminating element is sensitive to immersion media and prone to contamination, requiring precise positioning in sub-micrometer accuracy, which is challenging due to the complexity and cost of actuator systems, especially in immersion lithography where stringent tolerances affect image quality.

Innovation Solution

A lens with capacitive and/or inductive sensor units for determining the relative position between optical elements, allowing precise positioning in the x and y directions without the need for complex actuator systems, using cylindrical reference surfaces and sensor arrangements on an electrically insulating substrate for accurate measurement.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If an actuator system is provided for manipulating the terminating element in up to six degrees of freedom, then high positioning accuracy is achieved, but device complexity and costs increase

Engineering Contradiction:

Improvepositioning accuracyVSAvoidactuator system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical actuator systems with capacitive or inductive sensor arrangements that magnetically couple to the terminating element. These sensors non-contactively measure position in the x and y directions perpendicular to the optical axis, eliminating the need for mechanical actuators while achieving sub-micrometer positioning accuracy. The sensor arrangement uses electrical or magnetic fields instead of mechanical components to detect element position.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If the terminating element is made exchangeable to address contamination, then reliability is improved, but positioning accuracy becomes more difficult to maintain

Engineering Contradiction:

Improveoptical performance reliabilityVSAvoidpositioning accuracy

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent implements feedback through sensor arrangements that continuously monitor the position of the terminating element after exchange. The capacitive or inductive sensors detect deviations from the reference position and provide feedback signals that enable active correction, ensuring the element is repositioned with sub-micrometer accuracy regardless of manufacturing tolerances or handling variations during exchange.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If stringent requirements are made of the terminating element with regard to accuracy and tolerances, then image quality is improved, but ease of manufacture deteriorates

Engineering Contradiction:

Improveimage qualityVSAvoidmanufacturing difficulty

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent introduces sensor arrangements as intermediary measurement devices that bridge the gap between manufacturing tolerances and required image quality. The sensors provide real-time position feedback, allowing elements with moderate manufacturing tolerances to be actively positioned and corrected to achieve the stringent accuracy requirements for high-quality imaging, thereby relaxing manufacturing constraints.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

This solution enables high-accuracy positioning of the terminating element in the x and y directions with accuracies of 1 μm to 10 nm, reducing the complexity and cost of the actuator system while maintaining image quality, by using capacitive and inductive sensors for precise relative position determination.

Implementation Method 1

at least one sensor arrangement comprising at least one capacitive sensor unit for determining the relative position between a first optical element and a second optical element

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

at least one sensor arrangement comprising at least one inductive sensor unit for determining the relative position between a first optical element and a second optical element

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS9551940B2Lens comprising a plurality of optical element disposed in a housing

Publication Date: 2017.01.24 CARL ZEISS SMT GMBH

AI summary

The invention relates to a lens comprising several optical elements that are disposed in a lens housing. At least one sensor array encompassing at least one capacitive sensor unit and/or at least one inductive sensor unit is provided for determining the relative position between a first optical element and a second optical element or between a load-bearing structural element of the lens and a second optical element.