Compensating Stray Field Interference in Lithography Stage Apparatus

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Solution Overview

Problem

The influence of an electromagnetic motor's stray field on an electromagnetic actuator in lithographic apparatuses compromises the positioning accuracy, as the motor's magnetic field interferes with the actuator's operation, and traditional ferromagnetic shields are heavy and inefficient.

Innovation Solution

A stage apparatus is designed with an electromagnetic motor and actuator configuration where a current generator supplies a current to a coil to compensate for the stray field of the motor, reducing its impact on the actuator, thereby maintaining positioning accuracy without the need for heavy ferromagnetic shields.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If a ferromagnetic shield is provided between the electromagnetic motor and the electromagnetic actuator, then the influence of the motor's stray field on the actuator is reduced, but the shield becomes heavy and may itself be influenced by the electromagnetic field causing additional disturbances

Engineering Contradiction:

Improvestray field influenceVSAvoidshield weight

Core Design Contradiction:

Object-affected harmful factorsVSWeight of moving object

Solution Approach 1:

The patent replaces the mechanical ferromagnetic shield with an electromagnetic compensation system. A compensation coil generates a magnetic field that actively counteracts the stray field from the motor, eliminating the need for heavy passive shielding materials while maintaining actuator performance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the approach from passive physical barrier (ferromagnetic material) to active field parameter control. By adjusting the current in the compensation coil, the magnetic field parameters are dynamically controlled to neutralize the stray field's harmful effects on the actuator

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If the electromagnetic actuator is positioned close to the electromagnetic motor for compact design, then the stage apparatus size is reduced, but the positioning accuracy deteriorates due to stray field interference

Engineering Contradiction:

Improveapparatus compactnessVSAvoidpositioning accuracy

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The patent introduces a compensation coil as an intermediary element between the motor and actuator. This coil mediates the electromagnetic interaction by generating a counteracting field that protects the actuator from stray field interference, enabling close positioning without accuracy loss

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful stray field effect into a beneficial controlled interaction. By deliberately generating a compensating magnetic field through the coil, the previously harmful stray field influence is transformed into a controllable parameter that can be neutralized, allowing compact design without sacrificing precision

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 configuration effectively mitigates the interference from the electromagnetic motor's stray field, enhancing the positioning accuracy and operational efficiency of the stage apparatus while minimizing the weight and potential disturbances from ferromagnetic shields.

Implementation Method 1

a current generator (70) configured to provide a current to a coil (60) arranged between the electromagnetic motor and the electromagnetic actuator such that, in use, an effect of a stray field of the electromagnetic motor on the electromagnetic actuator is at least partly compensated by the current

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

an electromagnetic motor arranged to displace the object table over comparatively large distances

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Implementation Method 3

an electromagnetic actuator configured to position the object table over comparatively small distances with a high accuracy

Methodology Applied

Scientific EffectElectromagnetic force: Lorentz Force

Data Source

PatentUS7348752B1Stage apparatus and lithographic apparatus

Publication Date: 2008.03.25 ASML NETHERLANDS BV

AI summary

A stage apparatus and a lithographic apparatus comprising such a stage apparatus are described. The stage apparatus includes an electromagnetic motor arranged to displace an object table, an electromagnetic actuator configured to position the object table and a device configured to provide a current to the stage apparatus such that, in use, an effect of a stray field of the electromagnetic motor on the electromagnetic actuator is at least partly compensated by the current.