Lithography Stage Driving System Resonance Cancellation

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Solution Overview

Problem

In lithography processes for manufacturing electronic devices, achieving high overlay accuracy is hindered by resonance issues in substrate stages, particularly as substrate sizes increase, leading to instability and precision challenges in driving these stages.

Innovation Solution

A driving system that utilizes two measuring instruments to measure controlled variables at different sections of the plant, allowing for control inputs to be calculated and applied in a manner that opposes resonance modes, thereby stabilizing the drive and enhancing precision.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If the substrate stage size is increased to accommodate larger substrates, then the processing capability is improved, but the resonance frequency decreases and stability deteriorates

Engineering Contradiction:

Improvesubstrate stage areaVSAvoiddriving stability

Core Design Contradiction:

Area of stationary objectVSReliability

Solution Approach 1:

The substrate stage is divided into multiple sections with measurement points distributed across different locations. By segmenting the stage and measuring vibrations at multiple points, the system can identify and counteract resonance modes more effectively, maintaining stability despite the large overall size of the stage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Vibration sensors measure the actual vibration state of the substrate stage in real-time, and this feedback is used by the control system to generate counter-vibrations that cancel out the resonance. This closed-loop feedback mechanism allows the large stage to maintain stability by continuously compensating for resonance effects.

Inventive Principle:

Principle #23Feedback

2Area of stationary object

If the substrate stage size is increased, then the processing capability is improved, but the manufacturing precision deteriorates due to resonance

Engineering Contradiction:

Improvesubstrate stage areaVSAvoidoverlay accuracy

Core Design Contradiction:

Area of stationary objectVSManufacturing precision

Solution Approach 1:

The system intentionally generates mechanical vibrations through actuators that are synchronized with the measured resonance modes. By creating controlled vibrations that oppose the harmful resonance, the system eliminates the precision-degrading effects of natural resonance, allowing large substrates to be processed with high overlay accuracy.

Inventive Principle:

Principle #18Mechanical vibration

Solution Approach 2:

The system converts the harmful resonance vibrations into beneficial effects by measuring the resonance modes and generating counter-vibrations. The same vibrational mechanisms that cause precision problems are harnessed to cancel out the harmful resonance, transforming a detrimental phenomenon into a solution that maintains manufacturing precision on large substrates.

Inventive Principle:

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

3Measurement precision

If multiple measurement points are added to capture resonance modes, then the control accuracy is improved, but the device complexity increases

Engineering Contradiction:

Improvevibration measurement accuracyVSAvoidmeasurement system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The vibration measurement and control system is designed to serve multiple functions: it measures vibrations at multiple points, identifies resonance modes, generates counter-vibrations, and maintains precision across the entire large substrate stage. This multi-functional approach consolidates what would otherwise require separate systems, reducing overall complexity while achieving high measurement precision.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS9188878B2Driving system and driving method, exposure apparatus and exposure method, and driving system design method

Publication Date: 2015.11.17 NIKON CORP

AI summary

At a carriage that shows a resonance mode in opposite phase to a resonance mode shown by a plate table where an interferometer which measures a position (a first controlled variable) of a plate stage driven according to a control input is installed, another interferometer is installed which measures a position (the second controlled variable) of the plate stage. By using the interferometer and the another interferometer, it becomes possible to design a driving system robust in a high bandwidth that drives the plate stage.