Multi-Beam Charged Particle Inspection via Cathodoluminescence
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Solution Overview
Problem
Existing multi-beam scanning electron microscope methods require detectors or beam separation devices in the path of primary electron beams, necessitate lens adjustments, and are less effective for samples suited for transmission detection rather than secondary or backscattered detection.
Innovation Solution
A multi-beam charged particle apparatus with a multi-pixel photon detector and optical assembly to detect photons created by focused primary charged particle beams, allowing for simultaneous detection and distinguishing between adjacent beams, optionally using a cathodoluminescent layer to generate photons for improved detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detector or beam separation device is placed in the path of primary electron beams to detect signals, then signal detection capability is improved, but device complexity and obstruction of the beam path worsen
Solution Approach 1:
The patent introduces a cathodoluminescent layer as an intermediary substance that converts electron beam energy into photons. This mediator enables indirect detection of the electron beam signal without placing detectors in the beam path, thus improving signal detection capability while avoiding the complexity and obstruction issues of direct detection methods
Solution Approach 2:
The patent replaces the mechanical/electronic detection system (detectors in beam path) with an optical detection system. By using cathodoluminescence to convert electron beam interactions into photons, the system substitutes a mechanical detection approach with an optical one, allowing detection without obstructing the electron beam path
2Measurement precision
If lens excitation is adjusted to accommodate signal electron beams for detection, then detection capability is improved, but ease of operation worsens
Solution Approach 1:
The cathodoluminescent layer serves as a mediator that decouples the detection process from the lens excitation requirements. By converting electron beam interactions into photons that can be detected optically, the system eliminates the need to adjust lens excitation for signal electron beam detection, thereby improving ease of operation while maintaining detection capability
3Ease of operation
If secondary or backscattered electron detection is used, then ease of operation is maintained, but measurement precision worsens for samples suited for transmission detection
Solution Approach 1:
The patent substitutes secondary or backscattered electron detection with photon detection via cathodoluminescence. This replacement enables transmission-like detection capabilities while maintaining ease of operation, as the optical detection system does not require complex lens adjustments and can effectively detect samples suited for transmission detection
Solution Approach 2:
The patent changes the detection parameter from electron signal detection to photon detection. By utilizing cathodoluminescence to convert electron beam interactions into photons, the system alters the detection parameter to one that is better suited for transmission detection while maintaining operational simplicity
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
Enables efficient detection of photons from multiple focused primary charged particle beams without obstructing the beams or requiring lens adjustments, providing enhanced resolution and contrast mechanisms for sample inspection.
Implementation Method 1
an electro-magnetic lens system for directing said array of primary charged particle beams into an array of separate focused primary charged particle beams at the sample holder
Implementation Method 2
A phenomenon which causes the emission of photons due to the impact of charged particles on a material, in particular a luminescent material, is referred to as cathodoluminescence
Implementation Method 3
an optical assembly for conveying photons created by at least two adjacent focused primary charged particle beams of said array of separate focused primary charged particle beams to distinct and/or separate pixels or to distinct and/or separate groups of pixels of the multi-pixel photon detector
Data Source
AI summary
An apparatus for inspecting a sample includes a sample holder for holding the sample; a multi beam charged particle generator for generating an array of primary charged particle beams; an electro-magnetic lens system for directing the array of primary charged particle beams into an array of separate focused primary charged particle beams on the sample; a multi-pixel photon detector arranged for detecting photons created by the focused primary charged particle beams when the primary charged particle beams impinge on the sample or after transmission of said primary charged particle beams through the sample; and an optical assembly for conveying photons created by at least two adjacent focused primary charged particle beams of the array of separate focused primary charged particle beams to distinct and/or separate pixels or to distinct and/or separate groups of pixels of the multi-pixel photon detector.