Leveling Sensor Pattern Projection for Wafer Height Accuracy

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Solution Overview

Problem

Inspection tools for integrated circuits face challenges in maintaining accuracy and throughput due to limitations in detecting wafer displacement, which affects imaging resolution and throughput as IC component sizes shrink.

Innovation Solution

A charged-particle beam inspection system equipped with a leveling sensor that uses a light source to project a pattern with irregularities, allowing for high-accuracy detection of vertical displacement through cross-correlation with a reference image, enabling precise adjustment of sample height.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional leveling sensors are used in charged-particle beam inspection systems, then the system can operate, but the detection accuracy of vertical displacement is insufficient, leading to degraded imaging resolution

Engineering Contradiction:

Improvevertical displacement detection accuracyVSAvoidimaging resolution

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent introduces an optical intermediary system (light source projecting pattern through objective lens to sample) that mediates between the leveling sensor and the charged-particle beam inspection system. This optical intermediary enables high-precision vertical displacement detection by using optical projection and detection mechanisms that are more sensitive than direct charged-particle measurement, thereby improving both displacement detection accuracy and subsequent imaging resolution

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent changes the measurement parameter from direct charged-particle position measurement to optical pattern projection displacement measurement. By projecting a light pattern through the objective lens and detecting its displacement on the sample surface, the system achieves higher measurement precision for vertical displacement, which directly improves imaging resolution in the charged-particle beam inspection

Inventive Principle:

Principle #35Parameter changes

2Productivity

If conventional leveling sensors are used, then the system structure remains simple, but the throughput is limited due to inaccurate wafer displacement detection

Engineering Contradiction:

Improveinspection throughputVSAvoidwafer displacement detection accuracy

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The optical intermediary system enables high-speed, high-precision displacement detection that does not bottleneck the inspection throughput. The light-based measurement can be performed rapidly without affecting the charged-particle beam inspection flow, thereby improving throughput while maintaining high measurement precision

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The objective lens serves multiple functions: it is used both for the optical projection in the leveling sensor and for focusing the charged-particle beam in the inspection system. This multi-functionality allows the system to achieve high-precision displacement detection and high-throughput inspection without requiring separate dedicated components, thus improving productivity while maintaining measurement precision

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Measurement precision

If IC component sizes continue to shrink, then device density increases, but the accuracy and yield in defect detection deteriorate due to insufficient wafer displacement detection capability

Engineering Contradiction:

Improvedefect detection accuracyVSAvoidcapability to handle smaller feature sizes

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the detection parameter from low-precision direct measurement to high-precision optical interference-based measurement. The optical pattern projection method can detect sub-micron vertical displacements with high accuracy, enabling reliable defect detection even as IC component sizes shrink to smaller feature sizes, thereby improving measurement precision and adaptability simultaneously

Inventive Principle:

Principle #35Parameter changes

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

Enhances the detection of vertical displacement with high accuracy and efficiency, improving imaging resolution and throughput in charged-particle beam inspection systems.

Implementation Method 1

a light source configured to project a first pattern onto the sample and a detector configured to capture an image of a projected pattern after the first pattern is projected on the sample

Methodology Applied

Scientific EffectOptical projection: Light

Implementation Method 2

conducting a cross-correlation between the light intensity image and a reference image, and determining a vertical displacement of the sample based on the cross-correlation

Methodology Applied

Scientific EffectCross-correlation:

Data Source

PatentUS12451324B2Leveling sensor in multiple charged-particle beam inspection

Publication Date: 2025.10.21 ASML NETHERLANDS BV

AI summary

An improved leveling sensor and method for adjusting a sample height in a charged-particle beam inspection system are disclosed. An improved leveling sensor comprises a light source configured to project a first pattern onto a sample and a detector configured to capture an image of a projected pattern after the first pattern is projected on the sample. The first pattern can comprise an irregularity to enable a determination of a vertical displacement of the sample.