Exposure Apparatus Optical Characteristic Prediction

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Solution Overview

Problem

Existing exposure apparatuses face challenges in accurately predicting and correcting changes in the optical characteristics of projection optical systems due to temperature fluctuations, leading to inaccuracies in pattern transfer on substrates, particularly due to time lags in temperature-induced changes affecting the projection optical system's performance.

Innovation Solution

An exposure apparatus equipped with a temperature measuring device and a controller that uses a second-order lag response function to predict changes in optical characteristics, allowing for precise adjustment of image formation on the substrate by processing temperature data to correct magnification errors and other aberrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If temperature measurement is performed to predict optical characteristic changes, then prediction capability is improved, but prediction accuracy deteriorates due to time lag between temperature change and optical characteristic change

Engineering Contradiction:

Improveprediction capabilityVSAvoidprediction accuracy

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by measuring the temperature of the temperature measurement portion (which changes temperature before the projection optical system) in advance, and using this early temperature data to predict future optical characteristic changes. The controller predicts magnification errors and focus errors based on the measured temperature change and its rate of change, allowing correction to be made before the actual optical degradation occurs, thus overcoming the time lag problem.

Inventive Principle:

Principle #10Preliminary action

2Stability of the object's composition

If temperature control is strengthened to stabilize projection optical system, then optical characteristic stability is improved, but device complexity increases

Engineering Contradiction:

Improveoptical characteristic stabilityVSAvoiddevice complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent uses the temperature measurement portion as an intermediary element that indirectly reflects the thermal state affecting the projection optical system. Instead of directly controlling the projection optical system's temperature, the system measures temperature at a location that changes temperature first, uses this data to predict optical characteristic changes, and applies corrections through the magnification correction unit and focus correction unit. This indirect approach achieves stability without requiring direct thermal control of the optical system.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Manufacturing precision

If correction processing is performed based on temperature prediction, then manufacturing precision is improved, but processing time increases

Engineering Contradiction:

Improvepattern transfer accuracyVSAvoidprocessing time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent implements continuous temperature measurement and continuous prediction of optical characteristic changes, allowing real-time correction without interrupting the exposure process. The controller continuously monitors temperature changes, predicts magnification and focus errors, and applies corrections through the correction units while the exposure apparatus operates, eliminating the need for separate correction cycles and maintaining continuous productive action.

Inventive Principle:

Principle #20Continuity of useful action

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 approach enables accurate prediction and correction of optical changes, ensuring precise pattern transfer by effectively addressing the time lag issue, thereby improving the accuracy of pattern formation on substrates.

Implementation Method 1

Heat generated in the exposure apparatus may be transferred to the projection optical system upon heat conduction, convection, or thermal radiation between members that constitute the exposure apparatus

Methodology Applied

Scientific EffectThermal radiation: Thermal Radiation

Implementation Method 2

Methodology Applied

Scientific EffectHeat conduction: Conduction (thermal)

Implementation Method 3

Methodology Applied

Scientific EffectConvection: Convection

Implementation Method 4

the controller is configured to perform the prediction in accordance with a second-order lag response function to the change in temperature of the temperature measurement portion

Methodology Applied

Scientific EffectSecond-order lag response:

Data Source

PatentUS9383660B2Exposure apparatus and method of manufacturing device

Publication Date: 2016.07.05 CANON KK

AI summary

An exposure apparatus which includes a projection optical system and exposes a substrate to radiant energy via the projection optical system, includes a temperature measuring device configured to perform measurement of a temperature of a temperature measurement portion of the projection optical system, and a controller configured to perform prediction of a change in an optical characteristic of the projection optical system based on a change in temperature measured by the temperature measuring device, and to perform processing of reduction, based on the prediction, of a change in a state of an image formed on the substrate by the projection optical system, wherein the controller is configured to perform the prediction in accordance with a second-order lag response function to the change in temperature of the temperature measurement portion.