Per-site residual analysis for wafer metrology accuracy

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Solution Overview

Problem

Current metrology methods in semiconductor production face challenges in accurately optimizing measurement parameters across wafer sites, leading to systematic and non-systematic errors, which affect the precision and reliability of metrology measurements.

Innovation Solution

The method involves identifying residual components of metrology metrics per wafer site using computer processors and optimizing measurement parameters based on these components, employing zonal analysis to reduce errors and relate residuals to process variations, thereby enhancing metrology performance by combining different landscapes over the wafer area.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional metrology measurement methods are used with uniform parameters across the wafer, then the measurement process is simple and fast, but systematic errors and non-systematic errors reduce measurement precision

Engineering Contradiction:

Improvemetrology measurement precisionVSAvoidmeasurement parameter optimization complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent applies local quality by optimizing measurement parameters specifically for each wafer site based on identified residual components. Different sites receive tailored measurement parameters rather than uniform parameters, which reduces systematic and non-systematic errors at each location and improves overall measurement precision without requiring complete system redesign

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent segments the wafer into multiple sites and analyzes residual components separately for each site. This segmentation allows independent optimization of measurement parameters for each site based on its specific error characteristics, resolving the contradiction between measurement precision and optimization complexity by making the problem manageable at the site level rather than requiring full-wafer uniform optimization

Inventive Principle:

Principle #1Segmentation

2Measurement precision

If zonal analysis with spatially variable parameters is implemented, then measurement accuracy improves, but the analysis and optimization process becomes more complex

Engineering Contradiction:

Improvemetrology measurement accuracyVSAvoidresidual component analysis difficulty

Core Design Contradiction:

Measurement precisionVSDifficulty of detecting and measuring

Solution Approach 1:

The patent segments the complex residual analysis into site-specific components, identifying residual errors independently for each wafer site. This segmentation simplifies the detection and measurement process by breaking down the overall complex pattern into manageable site-level patterns, making zonal analysis more tractable while maintaining improved measurement accuracy

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes measurement parameters based on identified residual components at each site. By adapting parameters locally rather than using fixed uniform parameters, the system achieves higher measurement accuracy while the parameter changes are driven by automated residual analysis, which manages the complexity through systematic site-by-site processing

Inventive Principle:

Principle #35Parameter changes

3Reliability

If per-site optimization of measurement parameters is performed, then systematic errors are reduced, but the measurement and optimization time increases

Engineering Contradiction:

Improvemetrology measurement reliabilityVSAvoidparameter optimization time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent performs preliminary identification of residual components for each wafer site before final measurement optimization. This preliminary action characterizes the error patterns at each site in advance, allowing subsequent parameter optimization to be more efficient and targeted, thereby reducing the time penalty associated with per-site optimization while maintaining improved reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent applies local quality optimization where each site receives measurement parameters tailored to its specific residual error characteristics. This localized approach improves measurement reliability by addressing site-specific systematic errors, while the automation of the process and reuse of residual component patterns across similar sites helps manage the time investment required

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11249400B2Per-site residuals analysis for accurate metrology measurements

Publication Date: 2022.02.15 KLA CORP

AI summary

Systems, metrology modules and methods are provided, which identify, per wafer site, components of residuals from measurement of metrology metric(s), and optimize measurement parameters for each site, according to the identified residuals' components. Certain embodiments utilize metric landscapes to identify sensitive sites and/or to identify sites exhibiting highest accuracy, and corresponding metrics may be combined over the wafer to further enhance the metrology performance. Zonal analysis may be used to reduce the systematic errors, and disclosed per-site analysis may be used to further reduce the non-systematic error components, and relate the remaining residuals components to process variation over the wafer.