Annular On-Axis Charged Particle Detector Segmentation

Solution Overview

Problem

Current charged particle detectors in low voltage scanning electron microscopes (SEMs) face challenges in achieving high resolution and efficient signal collection due to the use of either single on-axis detectors, which suffer from non-uniform signal collection, or multiple off-axis detectors, which introduce spatial separation and second-order aberrations, complicating three-dimensional topographic imaging.

Innovation Solution

An annular in-lens on-axis symmetrically distributed multi-channel detection system is designed, featuring one or more light guide modules in a rotational symmetric configuration, allowing for efficient signal separation and amplification across multiple channels, enabling better resolution and three-dimensional imaging without the limitations of off-axis detectors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If multiple off-axis detectors are used to collect signals, then signal collection efficiency is improved, but spatial separation and second-order aberrations are introduced, complicating three-dimensional topographic imaging

Engineering Contradiction:

Improvesignal collection efficiencyVSAvoidthree-dimensional topographic imaging accuracy

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The detector is divided into multiple segments arranged in an annular configuration around the optical axis. Each segment independently collects signals from a specific angular range, and the segmented signals are processed separately to reconstruct three-dimensional topographic information without the aberrations introduced by off-axis detectors.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The detector transitions from a planar off-axis arrangement to a three-dimensional annular configuration surrounding the optical axis. This spatial reconfiguration allows simultaneous collection of signals from multiple angles while maintaining on-axis alignment, eliminating second-order aberrations while preserving signal collection efficiency.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If a single on-axis detector is used to simplify the system, then device complexity is reduced, but signal collection uniformity deteriorates

Engineering Contradiction:

Improvedetector configuration simplicityVSAvoidsignal collection uniformity

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The detector is divided into multiple segments arranged in an annular configuration around the optical axis. Each segment independently collects signals from a specific angular range, and the segmented signals are processed separately to reconstruct three-dimensional topographic information without the aberrations introduced by off-axis detectors.

Inventive Principle:

Principle #1Segmentation

3Loss of information

If off-axis detectors are positioned to collect secondary electrons, then topographic information is obtained, but spatial separation introduces distortions in imaging

Engineering Contradiction:

Improvetopographic information recoveryVSAvoidimaging accuracy

Core Design Contradiction:

Loss of informationVSManufacturing precision

Solution Approach 1:

The detector transitions from a planar off-axis arrangement to a three-dimensional annular configuration surrounding the optical axis. This spatial reconfiguration allows simultaneous collection of signals from multiple angles while maintaining on-axis alignment, eliminating second-order aberrations while preserving signal collection efficiency.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 annular in-lens on-axis detection system enhances topographic feature detection by providing a high-resolution, space-saving, and efficient means of collecting signals from secondary and back-scattered electrons, improving the accuracy of three-dimensional surface imaging without the distortions associated with off-axis configurations.

Implementation Method 1

a light guide rod that has a front face coated with a light-generating scintillator

Methodology Applied

Scientific EffectScintillation: Scintillation

Data Source

PatentUS7928383B2Charged particle system including segmented detection elements

Publication Date: 2011.04.19 ASML NETHERLANDS BV

AI summary

A charged particle detector consists of a plurality independent light guide modules assembled together to form a segmented in-lens on-axis annular detector, with a center hole for allowing the primary charged particle beam to pass through. One side of the assembly facing the specimen is coated with or bonded to scintillator material as the charged particle detection surface. Each light guide module is coupled to a photomultiplier tube to allow light signals transmitted through each light guide module to be amplified and processed separately. A charged particle detector is made from a single block of light guide material processed to have a cone shaped circular cutout from one face, terminating on the opposite face to an opening to allow the primary charged particle beam to pass through. The opposite face is coated with or bonded to scintillator material as the charged particle detection surface. The outer region of the light guide block is shaped into four separate light guide output channels and each light guide output channel is coupled to a photomultiplier tube to allow light signal output from each channel to be amplified and processed separately.