Lithographic Positioning System Torque Compensation

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Solution Overview

Problem

Vibrations caused by torque transferred from a balance mass to a base plate in lithographic apparatuses and positioning systems deteriorate the functioning of these systems.

Innovation Solution

A positioning system with first and second actuators and a controller, where the first actuator exerts an actuation force on a support coupled to a balance mass, and the controller and second actuator compensate for the resulting torque by exerting a compensation force, minimizing vibrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a balance mass is used to absorb reaction forces from the planar motor, then the positioning stability is improved, but vibrations are generated due to torque transfer to the base plate

Engineering Contradiction:

Improvepositioning stabilityVSAvoidvibrations

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

A torque compensation mechanism is introduced as an intermediary element between the balance mass and the base plate. This mechanism includes additional actuators that generate compensating forces to counteract the torque produced by the offset center of mass, thereby preventing vibration transmission to the base plate while maintaining the balance mass's stabilizing function

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system applies preliminary counteracting forces through the torque compensation mechanism before the vibrations can propagate. The control system continuously monitors the position and calculates the required compensation force in advance, applying it through additional actuators to neutralize the torque effect before it causes harmful vibrations

Inventive Principle:

Principle #9Preliminary anti-action

2Force

If the center of mass of the balance mass is offset from the support table to generate counteracting force, then the counterbalance effect is improved, but torque is generated that causes vibrations

Engineering Contradiction:

Improvecounteracting forceVSAvoidtorque-induced vibrations

Core Design Contradiction:

ForceVSObject-generated harmful factors

Solution Approach 1:

The system dynamically adjusts the compensation force parameters based on the offset distance and the position of the support table. By changing the magnitude and direction of the compensating force in real-time, the system maintains effective counterbalancing while eliminating the harmful torque effect that causes vibrations

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

A control system with feedback mechanisms continuously monitors the position of the support table and the forces involved. Based on this feedback, the system calculates and adjusts the compensation force required to counteract the torque, ensuring that the counterbalance effect is maintained without generating vibrations

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS9122173B2Positioning system, lithographic apparatus and device manufacturing method

Publication Date: 2015.09.01 ASML NETHERLANDS BV

AI summary

A positioning system to position a table within a base frame of a lithographic apparatus, the positioning system including first and second actuators and a controller. The first actuator exerting an actuation force on the table. The first actuator being connected to a balance mass constructed and arranged to absorb a reaction force of the first actuator. The controller and second actuator constructed and arranged to exert a compensation force and/or torque to compensate a torque caused by the actuation force exerted by the first actuator on the balance mass.