Objective Lens Electrode Layout for Cleaner SEM Electron Detection
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Solution Overview
Problem
In scanning electron microscopes (SEMs), secondary electrons pulled into the objective lens collide with electrodes, producing undesirable secondary electrons that degrade image quality and contaminate electrodes.
Innovation Solution
An objective lens design for SEMs, featuring a configuration of multiple electrodes with conical tips and through-holes, where the charged particle beam is focused through these holes, minimizing collisions between secondary electrons and electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a detector is disposed above the objective lens to detect secondary electrons pulled into the objective lens, then image quality is improved, but secondary electrons collide with electrodes producing noise and contaminating electrodes
Solution Approach 1:
The objective lens is divided into multiple separate electrodes (first electrode, second electrode, third electrode, and fourth electrode) arranged in sequence along the electron beam path. Each electrode has a through-hole and can be independently positioned and adjusted, allowing separate control of the electron beam path and secondary electron collection paths, thereby preventing harmful collisions while maintaining detection capability
Solution Approach 2:
The detector is positioned at the fourth electrode which is located in the body of the third electrode, creating a multi-dimensional arrangement where the charged particle beam passes through through-holes in all four electrodes while secondary electrons are collected by the detector in a different spatial dimension, avoiding collision with the main electrode structures
2Manufacturing precision
If multiple electrodes are arranged to focus charged particle beam through through-holes, then beam focusing is improved, but device complexity increases
Solution Approach 1:
The electrodes are arranged in a nested configuration where the second electrode is located within the first electrode with a gap, the third electrode is located within the second electrode with a gap, and the fourth electrode is located in the body of the third electrode. This nested arrangement achieves precise beam focusing through multiple through-holes while compacting the overall structure to reduce complexity
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 design reduces noise and contamination, enhancing image quality and extending the long-term reliability of the objective lens by preventing secondary electrons from colliding with high-potential electrodes.
Implementation Method 1
a first electrode exposed to face a sample; a second electrode configured to focus a charged particle beam to the sample
Implementation Method 2
a fourth electrode located in the body of the third electrode, wherein each of the first electrode, the second electrode, the third electrode, and the fourth electrode has a through-hole
Implementation Method 3
detect signals such as secondary electrons and backscattered electrons pulled into the objective lens
Data Source
AI summary
An objective lens for a charged particle beam apparatus that provides a charged particle beam to a sample, includes: a first electrode exposed to face a sample; a second electrode configured to focus a charged particle beam to the sample; a third electrode comprising a conical tip and a body extending from the tip; and a fourth electrode located in the body of the third electrode. Each of the first electrode, the second electrode, the third electrode, and the fourth electrode has a through-hole, and the charged particle beam is provided to the sample through the through-hole in response to a voltage applied.