Lithography Exposure Method with Optical Characteristic Prediction

Solution Overview

Problem

In lithography processes for semiconductor devices, accurately transferring a mask pattern onto a substrate is challenging due to optical characteristic fluctuations in the projection optical system caused by heat absorption, leading to inefficiencies in measurement and prediction of optical characteristics, which can result in unnecessary measurements and reduced throughput.

Innovation Solution

An exposure method that involves a first exposure process for measuring and correcting optical characteristics, followed by a second process using a prediction formula with coefficients determined from previous measurements, where the transition to the second process occurs once the coefficients are judged to have converged, thereby optimizing the use of measurement data and reducing errors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If optical characteristics are frequently measured to ensure accuracy, then manufacturing precision is improved, but productivity deteriorates due to reduced throughput

Engineering Contradiction:

Improveoptical characteristic measurement accuracyVSAvoidthroughput

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent performs optical characteristic measurements in advance during a first exposure process, determines prediction formula coefficients from these measurements, and stores them for later use. This preliminary action allows subsequent second exposure processes to use prediction-based corrections without repeated measurements, thereby maintaining manufacturing precision while improving productivity through reduced measurement frequency.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If prediction formula coefficients are used to reduce measurements, then productivity is improved, but measurement precision deteriorates due to potential errors in prediction

Engineering Contradiction:

ImprovethroughputVSAvoidoptical characteristic prediction accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where optical characteristics are measured periodically in the first exposure process, and the measured values are used to update and refine the prediction formula coefficients. This feedback loop ensures that the prediction model remains accurate over time while minimizing the frequency of measurements, thus balancing productivity improvement with maintained measurement precision.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs optical characteristic measurements in advance during a first exposure process, determines prediction formula coefficients from these measurements, and stores them for later use. This preliminary action allows subsequent second exposure processes to use prediction-based corrections without repeated measurements, thereby maintaining manufacturing precision while improving productivity through reduced measurement frequency.

Inventive Principle:

Principle #10Preliminary action

3Measurement precision

If measurements are performed to verify prediction accuracy, then measurement precision is improved, but productivity deteriorates due to unnecessary measurements

Engineering Contradiction:

Improveprediction verification accuracyVSAvoidthroughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent performs optical characteristic measurements in advance during a first exposure process, determines prediction formula coefficients from these measurements, and stores them for later use. This preliminary action allows subsequent second exposure processes to use prediction-based corrections without repeated measurements, thereby maintaining manufacturing precision while improving productivity through reduced measurement frequency.

Inventive Principle:

Principle #10Preliminary 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 enhances throughput by minimizing unnecessary measurements and improving the accuracy of optical characteristic predictions, allowing for more efficient pattern transfer with reduced measurement errors, thus improving the overall manufacturing process.

Implementation Method 1

a portion of the exposure light is absorbed in the projection optical system, optical characteristics of the projection optical system fluctuate by the influence of heat generated thereby

Methodology Applied

Scientific EffectAbsorption (EM radiation): Absorption (EM radiation)

Data Source

PatentUS10394134B2Exposure method, exposure apparatus, and method of manufacturing article

Publication Date: 2019.08.27 CANON KK

AI summary

The present invention provides an exposure method for repeatedly performing an exposure process for exposing a substrate via a projection optical system, the method comprising a first exposure process for measuring optical characteristics of the projection optical system, and exposing the substrate while correcting the optical characteristics based on a result of the measurement; a second exposure process for exposing the substrate while correcting the optical characteristics based on a result of estimating the optical characteristics by a prediction formula, wherein the first exposure process is repeatedly performed, and the second exposure process is started after the first exposure process where it is judged that the determined coefficient of the prediction formula has converged.