Nested Magnetic Shields for Wien Filter Stray Field Isolation
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Solution Overview
Problem
Existing semiconductor inspection apparatuses face challenges in maintaining high resolution due to stray and external magnetic fields interfering with the Wien filter, leading to adverse optical characteristics and reduced resolution, especially when using high-current electron beams and devices with magnetic lenses or external magnetic fields nearby.
Innovation Solution
A Wien filter is designed with multiple electromagnetic poles inside a magnetic lens barrel, featuring a first magnetic shield covered by a second magnetic shield, both supported by non-magnetic and magnetic materials respectively, to create a stable magnetic field and prevent stray or external magnetic interference, enhancing the magnetic shielding effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Wien filter and magnetic lens are installed near one another to shorten the optical path length, then the resolution drop due to space charge effect is suppressed, but stray magnetic field from the magnetic lens enters into the Wien filter causing optical axis bending and resolution drop
Solution Approach 1:
The Wien filter is disposed inside the lens barrel, with the first magnetic shield covering the electromagnetic poles and the second magnetic shield covering the first magnetic shield, creating a nested structure that isolates the Wien filter from external magnetic fields while maintaining compact positioning near the magnetic lens
Solution Approach 2:
The first and second magnetic shields act as intermediary elements between the Wien filter and the external magnetic environment, blocking stray magnetic fields from the magnetic lens and other devices while allowing the Wien filter to remain positioned near the lens for short optical path length
2Adaptability or versatility
If another device is installed in the area around the electron beam inspection apparatus, then functionality is enhanced, but external magnetic field generated by this device enters into the Wien filter causing optical characteristics deterioration
Solution Approach 1:
The nested magnetic shield structure (first magnetic shield inside second magnetic shield) creates multiple layers of protection that can block external magnetic fields from various devices while allowing the Wien filter to coexist with other apparatus components in the inspection system
Solution Approach 2:
The magnetic shields serve as intermediary barriers between the Wien filter and external devices, enabling the inspection apparatus to incorporate additional functional devices without compromising the magnetic field stability required for the Wien filter operation
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 prevents stray and external magnetic fields from disturbing the desired magnetic field within the Wien filter, maintaining high resolution and optical performance even with high-current electron beams and nearby magnetic devices.
Implementation Method 1
a first magnetic shield disposed so as to cover the area around the plurality of electromagnetic poles; and a second magnetic shield disposed so as to cover the area around the first magnetic shield
Implementation Method 2
the relationship between the electric and magnetic fields for causing the electron beam to propagate in a straight line (the Wien condition)
Data Source
AI summary
A Wien filter to be disposed inside a lens barrel made of a magnetic material includes: a plurality of electromagnetic poles disposed at equal angular intervals about a center axis of the lens barrel; a first magnetic shield disposed so as to cover the area around the plurality of electromagnetic poles; and a second magnetic shield disposed so as to cover the area around the first magnetic shield. The first magnetic shield is supported by a first support member made of a non-magnetic material provided at an inner surface of the second magnetic shield. The second magnetic shield is supported by a second support member made of a magnetic material provided at an inner surface of the lens barrel.