Electrostatic Lenses for Secondary Electron Detection in SEM
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In scanning electron microscopes, especially CD-SEMs, it is challenging to detect secondary electrons with specific energy or radiation angles due to their loss before reaching detectors, leading to insufficient contrast and inaccurate measurements, as existing methods either fail to control secondary electron trajectories effectively or result in inefficient detection.
Innovation Solution
A charged particle beam device is proposed, incorporating an objective lens, a detector, a deflector, and multistage electrostatic lenses that focus and separate secondary electrons from the primary beam axis, along with an energy spectroscope and negative voltage application, to control and detect secondary electrons efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an orthogonal electromagnetic field deflector is used to guide secondary electrons to a detector, then detection efficiency of secondary electrons is improved, but trajectories of secondary electrons until reaching the deflector cannot be controlled and depend on optical conditions
Solution Approach 1:
An electrostatic lens is introduced as an intermediary component between the sample and the orthogonal electromagnetic field deflector. This lens focuses secondary electrons emitted from the sample onto the deflector, providing controlled trajectory management. The electrostatic lens acts as a mediator that bridges the gap between the sample and deflector, ensuring that secondary electrons are properly directed to the deflector regardless of variations in objective lens conditions.
Solution Approach 2:
The trajectory control function is segmented into two distinct stages: (1) the electrostatic lens handles the initial focusing of secondary electrons from the sample, and (2) the orthogonal electromagnetic field deflector handles the subsequent deflection and guiding of electrons to the detector. This segmentation allows each component to specialize in a specific aspect of trajectory control, improving overall system performance.
2Measurement precision
If a method using trapping electrodes to cause secondary electron trajectories to converge is used, then secondary electrons with predetermined energy or radiation angle can be caused to converge, but secondary electrons with different energy or radiation angle cannot be controlled simultaneously
Solution Approach 1:
The electrostatic lens is designed to perform multiple functions simultaneously: it focuses electrons of different energies and radiation angles onto a common focal point, while also maintaining the ability to work in conjunction with the orthogonal electromagnetic field deflector for selective detection. This multi-functional capability allows the system to adapt to different detection requirements without requiring separate specialized components for each energy or angle range.
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
This configuration allows for high-efficiency detection of charged particles by converging secondary electrons with different energies and angles onto a common point, reducing losses and improving detection efficiency, thereby enhancing measurement accuracy and contrast in SEM images.
Implementation Method 1
a plurality of electrodes which are disposed between the deflector and the objective lens, and form a plurality of electrostatic lenses focusing the charged particles emitted from the sample toward a deflection point of the deflector
Implementation Method 2
a deflector that deflects charged particles emitted from the sample so that the charged particles are more separated from an axis than the charged particle beam
Data Source
AI summary
The purpose of the present invention is to reduce the amount of charged particles that are lost by colliding with the interior of a column of a charged particle beam device, and detect charged particles with high efficiency. To achieve this purpose, proposed is a charged particle beam device provided with: an objective lens that focuses a charged particle beam; a detector that is disposed between the objective lens and a charged particle source; a deflector that deflects charged particles emitted from a sample such that the charged particles separate from the axis of the charged particle beam; and a plurality of electrodes that are disposed between the deflector and the objective lens and that form a plurality of electrostatic lenses for focusing the charged particles emitted from the sample on a deflection point of the deflector.