E-Beam Overlay Measurement for Buried Feature SEM Tuning

Solution Overview

Problem

Current methods for determining optimal scanning electron microscope (SEM) parameters for overlay measurement of buried features in integrated circuits (ICs) rely on trial and error, resulting in poor measurement quality and low throughput.

Innovation Solution

A system and method for optimizing SEM parameters, including determining acquisition time and landing energy based on wafer stack characteristics and backscattered electron yields, using a controller and optimization model to automate the process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If trial and error method is used to determine optimal SEM parameters, then measurement quality may be improved, but throughput decreases and time consumption increases

Engineering Contradiction:

Improveoverlay measurement qualityVSAvoidmeasurement throughput

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The system performs preliminary actions by pre-calculating optimal SEM parameters (landing energy, beam current, acquisition time) based on wafer stack characteristics before actual measurement. This allows the measurement process to start immediately with optimized parameters, eliminating the need for time-consuming trial and error during production, thus improving both measurement quality and throughput

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces the manual trial-and-error mechanical adjustment process with an automated computational system. The controller uses algorithms to calculate optimal parameters based on input characteristics, substituting human operator intuition and iterative adjustment with systematic computational optimization, thereby improving efficiency and consistency

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If trial and error method is used to determine optimal SEM parameters, then measurement quality may be improved, but acquisition time increases

Engineering Contradiction:

Improveoverlay measurement qualityVSAvoidacquisition time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The system performs preliminary actions by pre-calculating optimal SEM parameters (landing energy, beam current, acquisition time) based on wafer stack characteristics before actual measurement. This allows the measurement process to start immediately with optimized parameters, eliminating the need for time-consuming trial and error during production, thus improving both measurement quality and throughput

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system optimizes measurement acquisition time by dynamically adjusting key parameters including beam landing energy, beam current, and acquisition time based on wafer stack characteristics. By changing these parameters to optimal values calculated from material properties and feature geometry, the system achieves high measurement quality with reduced acquisition time

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If non-optimized SEM parameters are used, then device complexity is reduced, but measurement precision deteriorates

Engineering Contradiction:

Improveparameter optimization complexityVSAvoidoverlay measurement quality

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The system performs self-service by automatically determining optimal SEM parameters based on input wafer stack characteristics without requiring external optimization tools or complex manual adjustment. The controller uses the provided material properties and feature geometry to calculate and apply optimal parameters, making the system self-sufficient and avoiding additional device complexity while maintaining high measurement precision

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system optimizes measurement acquisition time by dynamically adjusting key parameters including beam landing energy, beam current, and acquisition time based on wafer stack characteristics. By changing these parameters to optimal values calculated from material properties and feature geometry, the system achieves high measurement quality with reduced acquisition time

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

Improves overlay measurement efficiency by optimizing SEM settings, leading to higher throughput and better measurement quality.

Implementation Method 1

a plurality of backscattered electron (BSE) yields detected at a plurality of features on the wafer stack

Methodology Applied

Scientific EffectBackscattered electron detection: Scattering

Data Source

PatentUS20250231129A1E-beam optimization for overlay measurement of buried features

Publication Date: 2025.07.17 ASML NETHERLANDS BV

AI summary

Systems, non-transitory computer readable medium, and methods for determining one or more parameters used by an e-beam for an overlay measurement are disclosed. In some embodiments, the method comprises determining an acquisition time for the overlay measurement of a wafer stack based on a plurality of characteristics of the wafer stack and a plurality of backscattered electron (BSE) yields detected at a plurality of features on the wafer stack. The method also comprises determining the one or more parameters including a landing energy of the e-beam based on optimization of the acquisition time for the overlay measurement.