SEM Backscattered Electron Detector Charge Control
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Solution Overview
Problem
In scanning electron microscopes, the electrical charge accumulated by the backscattered electron detector can alter the path of secondary electrons, leading to fluctuations in signal detection, which affects the reproducibility of inspection and measurement results, especially when observing insulator samples.
Innovation Solution
A scanning electron microscope system that includes a backscattered electron detection system controller to apply a voltage to the backscattered electron detector and a device-control computer to monitor the electrical charge based on signal intensity from the secondary electron detector, allowing for adjustments to prevent charge accumulation and maintain signal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the backscattered electron detector is disposed between the sample and the objective lens to detect backscattered electrons, then the detection capability of backscattered electrons is improved, but the electrical charge accumulated on the detector causes the path of secondary electrons to change, leading to signal instability
Solution Approach 1:
A voltage application unit is introduced as an intermediary component between the backscattered electron detector and the electrical charge it accumulates. This unit applies a controlled voltage to the backscattered electron detector, serving as a mediator to counteract the harmful electrical charge and prevent its influence on secondary electron paths, thereby resolving the contradiction between detection capability and signal stability
Solution Approach 2:
The system implements a feedback mechanism where the state of electrical charge on the backscattered electron detector is monitored, and a voltage is applied in response to maintain signal stability. The voltage application is controlled based on the detected charge state, creating a closed-loop system that automatically compensates for charge accumulation effects
2Productivity
If the primary electrons are applied to the sample with high current to improve imaging speed, then the productivity is improved, but the electrical charge accumulation on the backscattered electron detector increases, causing greater signal fluctuations
Solution Approach 1:
The voltage application unit operates in a feedback-controlled manner, continuously monitoring the electrical charge state on the backscattered electron detector and adjusting the applied voltage accordingly. This allows the system to maintain signal reproducibility even when operating at high primary electron currents for improved imaging speed
Solution Approach 2:
The system dynamically changes the voltage parameter applied to the backscattered electron detector based on operating conditions. By adjusting this voltage parameter in response to charge accumulation, the system can maintain reliable signal detection while operating at higher productivity levels
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 solution reduces or avoids fluctuations in secondary electron detection signals due to electrical charges, ensuring highly reliable inspection and measurement results by maintaining signal stability and reproducibility.
Implementation Method 1
backscattered electrons emitted from the sample in response to the primary electrons impinging on the sample
Implementation Method 2
Signal electrons (herein, low-energy signal electrons are referred to as secondary electrons) are emitted from the sample in response to the primary electrons impinging on the sample
Implementation Method 3
focuses and applies the electrons to a surface of a sample using an electrostatic lens or electromagnetic lens
Implementation Method 4
focuses and applies the electrons to a surface of a sample using an electrostatic lens or electromagnetic lens
Implementation Method 5
apply a voltage to the backscattered electron detector... detect a state of an electrical charge carried by the backscattered electron detector
Data Source
AI summary
A scanning electron microscope includes an electron-optical system including an electron source and an objective lens, a stage on which a sample is placed, a secondary electron detector disposed adjacent to the electron source relative to the objective lens and configured to detect secondary electrons, a backscattered electron detector disposed between the objective lens and the stage and configured to detect backscattered electrons, a backscattered electron detection system controller configured to apply a voltage to the backscattered electron detector, and a device-control computer configured to detect a state of an electrical charge carried by the backscattered electron detector based on signal intensity at the secondary electron detector when the primary electrons are applied to the sample with a predetermined voltage applied to the backscattered electron detector.