Backscattered Electron Detector Voltage Control for Stable Beam Imaging
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Solution Overview
Problem
In charged particle beam systems, particularly with semi-in-lens type objective lenses, the close proximity of electrostatic electrodes to the sample causes severe fluctuations in the electric field, leading to unstable charging states that can adversely affect image contrast and measurement reproducibility, especially when high-quality images with high throughput are required.
Innovation Solution
A charged particle beam system that includes a backscattered electron detector positioned between the objective lens and the sample stage, which adjusts the electric field on the sample by controlling the voltage applied to the detector, thereby stabilizing the electric field and maintaining high throughput for image acquisition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If electrostatic electrodes are positioned close to the sample for focus adjustment, then focus control capability is improved, but electric field fluctuations increase causing charging state instability
Solution Approach 1:
The system measures the actual charging state of the sample and feeds this information back to the control electrode, which then adjusts the electric field dynamically to compensate for fluctuations and maintain stable charging conditions despite the close positioning of electrostatic electrodes
Solution Approach 2:
A control electrode is introduced as an intermediary element between the objective lens and the sample. This control electrode acts as a mediator that can adjust the electric field independently, allowing the electrostatic electrodes to maintain their close positioning for focus control while the control electrode compensates for the resulting electric field fluctuations
2Productivity
If backscattered electron detector is disposed directly above the sample for effective detection, then detection efficiency is improved, but electric field instability on the sample surface increases
Solution Approach 1:
The control electrode serves as an intermediary that decouples the detector's close positioning (which improves detection efficiency) from its adverse effect on electric field stability. The control electrode compensates for the electric field disturbances caused by the detector's proximity to the sample
3Measurement precision
If high acceleration voltage is used to obtain backscattered electron images of deep structures, then measurement capability of deep holes and grooves is improved, but primary electron beam deflection by charging increases
Solution Approach 1:
The control electrode applies a compensating electric field in advance to counteract the charging effects that would otherwise deflect the primary electron beam. By preemptively adjusting the electric field to offset expected charging, the system maintains beam stability even when using high acceleration voltages for deep structure imaging
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 effectively corrects electric field fluctuations, improving image quality and measurement reproducibility while maintaining high throughput by dynamically adjusting the electric field on the sample, thus addressing the instability caused by the proximity of electrostatic electrodes.
Implementation Method 1
a backscattered electron detector... that adjusts a focus of a charged particle beam
Implementation Method 2
an electrostatic lens... that adjusts a focus of a charged particle beam with which a sample is irradiated
Implementation Method 3
an objective lens... that adjusts a focus of a charged particle beam
Data Source
AI summary
An object of the invention is to acquire a high-quality image while maintaining an improvement in throughput of image acquisition (measurement (length measurement)). The present disclosure provides a charged particle beam system including a charged particle beam device and a computer system configured to control the charged particle beam device. The charged particle beam device includes an objective lens, a sample stage, and a backscattered electron detector that is disposed between the objective lens and the sample stage and that adjusts a focus of a charged particle beam with which a sample is irradiated. The computer system adjusts a value of an electric field on the sample in accordance with a change in a voltage applied to the backscattered electron detector.