Electron Beam Size Measurement Stabilizing Sample Potential
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Solution Overview
Problem
Conventional electron-beam size measuring apparatuses face challenges in maintaining sample surface potential stability during dimensional measurements, especially for nonconductive or floating conductive samples, leading to image distortion and inaccurate dimensional data due to charging effects.
Innovation Solution
An electron-beam size measuring apparatus with an electron beam irradiating system, detection system, distance measurement system, and control system that adjusts the sample stage height and applies a predetermined control voltage to a secondary electron control electrode to maintain a constant sample surface potential, using a calibration sample to determine optimal voltage and distance settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electron beam irradiation is applied to inspect or measure a sample, then dimensional measurement capability is achieved, but sample surface charging occurs causing image quality instability and measurement inaccuracy
Solution Approach 1:
A conductive layer is introduced as an intermediary between the sample surface and the electron beam irradiation. This conductive layer serves as a charge dissipation path, preventing charge accumulation on the sample surface while allowing the electron beam to continue inspecting or measuring the underlying sample structure, thereby maintaining both measurement capability and image stability
Solution Approach 2:
The electrical conductivity parameter of the sample surface is modified by depositing a conductive layer. This changes the electrical properties of the surface from insulating or high-resistance to conductive, enabling charge dissipation while preserving the sample's original dimensional and structural characteristics for accurate measurement
2Productivity
If electron beam irradiation continues on a sample, then measurement coverage increases, but charging effect accumulates causing progressive image distortion and dimensional relationship loss
Solution Approach 1:
The conductive layer acts as a continuous charge dissipation pathway that prevents charge accumulation even during extended irradiation periods. This allows the measurement process to cover larger areas and longer durations without the charging effects that would otherwise cause progressive image distortion and loss of dimensional relationships
Solution Approach 2:
The conductive layer is deposited on the sample surface before the electron beam measurement process begins. This preliminary preparation ensures that the surface is pre-equipped with charge dissipation capability, preventing charging effects from developing during the entire measurement sequence and maintaining dimensional accuracy throughout
3Reliability
If a conductive layer is deposited on the entire sample surface to prevent charging, then charging prevention is achieved, but measurement of specific pattern features becomes difficult due to layer interference
Solution Approach 1:
Instead of making the entire sample surface uniformly conductive, the conductive layer is applied selectively only in regions where charge dissipation is needed while leaving other regions untouched. This localized approach prevents charging in critical areas while maintaining the ability to measure specific pattern features in areas where the conductive layer does not interfere
Solution Approach 2:
The sample surface is divided into different functional zones: areas with conductive layer deposition for charge dissipation and areas without deposition for precise pattern feature measurement. This segmentation allows simultaneous achievement of charging prevention and accurate pattern measurement by treating different regions differently
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 approach ensures high accuracy in dimensional measurements by maintaining the sample surface potential within a stable range, preventing charging-induced image distortions and ensuring precise measurement of dimensions with minimal error.
Implementation Method 1
converting the amount of secondary electrons or the like to luminance
Implementation Method 2
the irradiated surface becomes charged positively or negatively by a difference in the amount of charge between charged particles entering the sample and charged particles emitted from the sample
Implementation Method 3
a voltage from an electrode disposed right above the sample pushes back secondary electrons emitted from the sample surface
Data Source
AI summary
An electron-beam size measuring apparatus includes: electron beam irradiating means that irradiates an electron beam on a surface of a sample; detection means that detects electrons emitted from the sample; distance measurement means that measures the distance between the sample and a secondary electron control electrode of the detection means; a stage on which the sample is mounted; and control means which adjusts the height of the stage so that the distance measured by the distance measurement means would be equal to a predetermined fixed distance, which applies a control voltage to the secondary electron control electrode of the detection means, the control voltage predetermined so as to allow the sample surface potential to become constant with the sample positioned at the fixed distance, and which causes the electron beam to be irradiated by applying a predetermined accelerating voltage. The stage may include holding means that does not electrically connect the sample thereto, and moving means that moves the sample up and down.