Metrology Data Correction Using Focus Index Correlation

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Solution Overview

Problem

Current patterning processes in lithography face challenges in accurately correcting metrology data, particularly due to variations in focus and dose, which affect the quality of the data obtained from metrology tools, leading to inaccurate measurements and process adjustments.

Innovation Solution

A method is introduced that involves obtaining metrology data and a quality metric, establishing a correlation between the two, and determining corrections using a computing system-based correction model. This model uses a focus index derived from local phase coherence maps to correct for focus-related variations independently of dose variations, allowing for real-time adjustments during the patterning process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional metrology data collection methods are used, then the data collection process is simple, but the measurement precision deteriorates due to focus and dose variations

Engineering Contradiction:

Improvemetrology data accuracyVSAvoidcorrection system complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements a feedback mechanism where metrology data is collected, quality metrics are computed to assess data quality, corrections are determined based on the quality metrics, and the corrections are applied to the metrology data. This closed-loop feedback system continuously monitors and adjusts for focus and dose variations, thereby maintaining high measurement precision without requiring complex hardware modifications.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent introduces quality metrics as an intermediary element between raw metrology data and corrected measurements. These quality metrics serve as mediators that quantify data quality based on focus and dose conditions, enabling the system to identify and correct problematic measurements without directly modifying the metrology collection process itself.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If quality metrics are computed and corrections are applied to all metrology data, then the manufacturing precision improves, but the processing time increases

Engineering Contradiction:

Improvepattern dimension accuracyVSAvoiddata processing time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The patent applies local quality assessment by computing quality metrics specifically for metrology data affected by focus and dose variations. Rather than uniformly processing all data, the system identifies regions or data points where quality degradation occurs and applies corrections selectively to those specific areas, thereby reducing overall processing time while maintaining manufacturing precision where it matters most.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the parameter space by introducing quality metrics as additional dimensions for data evaluation. By transforming raw metrology data into quality-assessed measurements with associated correction factors, the system enables more efficient processing through parameter-based filtering and prioritization of corrections based on their impact on manufacturing precision.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If focus variations are corrected independently of dose variations, then the measurement precision for focus-related parameters improves, but the system complexity increases

Engineering Contradiction:

Improvefocus measurement accuracyVSAvoidcorrection model complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the correction process into distinct components: quality metric computation, correction determination, and correction application. By dividing the complex task of simultaneous focus and dose correction into separate, modular steps, the system achieves high measurement precision for focus parameters while managing system complexity through structured decomposition of the correction model.

Inventive Principle:

Principle #1Segmentation

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

The method enhances the accuracy and robustness of metrology data by reducing the impact of focus and dose-related errors, enabling more precise process control and improving the quality of patterned substrates by generating corrected maps for parameters like critical dimensions and overlay.

Implementation Method 1

Methodology Applied

Scientific EffectLocal phase coherence:

Data Source

PatentUS12189307B2Metrology data correction using image quality metric

Publication Date: 2025.01.07 ASML NETHERLANDS BV

AI summary

A method for correcting metrology data of a patterning process. The method includes obtaining (i) metrology data of a substrate subjected to the patterning process and (ii) a quality metric (e.g., a focus index) that quantifies a quality of the metrology data of the substrate; establishing a correlation between the quality metric and the metrology data; and determining a correction to the metrology data based on the correlation between the quality metric and the metrology data.