Electron Microscope Magnetic Body Suppresses Beam Drift
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Solution Overview
Problem
Scanning electron microscopes face challenges in minimizing image blur due to beam drift caused by charging on insulator samples, particularly when observing samples with resist coatings, as existing solutions either fail to completely remove charging effects or degrade resolution.
Innovation Solution
An electron microscope configuration featuring a magnetic body with a continuous, rotationally symmetric structure and a larger inside diameter than the upper pole piece of the objective lens, positioned between the objective lens and the sample, along with a non-magnetic body to control potential gradients and reduce beam drift, while maintaining high resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a magnetic pole structure of semi-in-lens type is used to allow space below the objective lens for handling larger samples, then the sample handling capability is improved, but high magnetic field acts on the sample surface causing beam drift and image blur
Solution Approach 1:
The magnetic pole structure is segmented into multiple pole pieces arranged in a specific pattern. Instead of using a single large pole piece, the invention divides the magnetic field generation into multiple smaller poles that create a more uniform magnetic field distribution, reducing the high magnetic field concentration on the sample surface while maintaining the space for large sample handling.
Solution Approach 2:
The invention introduces asymmetric positioning of pole pieces relative to the sample plane. By strategically placing pole pieces at different distances and angles from the sample, the magnetic field is distributed more evenly across the sample surface, preventing localized high magnetic field regions that cause beam drift, while preserving the working space below the objective lens.
2Object-affected harmful factors
If incident energy is increased to bring the sample surface into a positively charged state for charging control, then charging effects are reduced, but measurement precision cannot be established for samples with resist coatings
Solution Approach 1:
The invention changes the magnetic field parameters (strength distribution, spatial configuration) rather than relying solely on energy parameter adjustments. By optimizing the magnetic pole structure to create a uniform magnetic field, secondary electron emission is enhanced without requiring high incident beam energy, thus maintaining measurement precision for resist-coated samples while effectively reducing charging effects.
Solution Approach 2:
The magnetic pole structure acts as an intermediary that mediates between the electron beam and the sample surface. By introducing a controlled magnetic field environment, the invention facilitates secondary electron emission and charging control without directly increasing beam energy, thereby protecting the sample from damage while maintaining measurement precision.
3Use of energy by stationary object
If a magnetic disc is provided around the pole piece gap to improve magnetic field generation efficiency and reduce power consumption, then power consumption is reduced, but resolution is significantly degraded
Solution Approach 1:
Instead of using a two-dimensional magnetic disc configuration that creates stray fields, the invention transitions to a three-dimensional arrangement of pole pieces positioned at specific spatial coordinates. This dimensional change allows for more precise control of magnetic field lines, concentrating the field where needed while minimizing stray fields that would degrade resolution, and enables efficient magnetic field generation with reduced power consumption.
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 effectively minimizes image blur by suppressing beam drift and maintaining high resolution, even when observing samples with resist coatings, by optimizing magnetic field distribution and reducing charging effects.
Implementation Method 1
A magnetic body with a continuous structure and an inside diameter larger than an inside diameter of an upper pole piece that forms an objective lens is provided between the objective lens and the sample
Implementation Method 2
accelerate electrons emitted from an electron source of thermal type or field emission type to form a thin electron beam (primary electron beam) using an electrostatic lens or a magnetic lens
Implementation Method 3
accelerate electrons emitted from an electron source of thermal type or field emission type to form a thin electron beam (primary electron beam) using an electrostatic lens or a magnetic lens
Implementation Method 4
detect a secondary signal, for example, secondary electron or backscattered electron secondarily generated from the sample resulting from radiation of the primary electron beam
Data Source
AI summary
A scanning electron microscope suppresses a beam drift by reducing charging on a sample surface while suppressing resolution degradation upon observation of an insulator sample. An electron microscope includes an electron source and an objective lens that focuses an electron beam emitted from the electron source, which provides an image using a secondary signal generated from the sample irradiated with the electron beam. A magnetic body with a continuous structure and an inside diameter larger than an inside diameter of an upper pole piece that forms the objective lens is provided between the objective lens and the sample.