Magnetic Shielding Plates for Electron Beam Stray Field Mitigation
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Solution Overview
Problem
In semiconductor manufacturing, multi-column inspection systems face challenges with beam deflection due to stray magnetic fields generated by permanent magnets, leading to reduced accuracy and longer time in detecting and fixing yield problems.
Innovation Solution
The implementation of a shielding plate system with multiple apertures and a nickel-iron alloy composition, strategically placed across the electron beam columns to mitigate stray magnetic fields, improving beam alignment and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If permanent magnets are used to condense and focus electron beams in multi-column inspection systems, then beam condensation and focusing capabilities are improved, but stray magnetic fields are generated causing beam deflection and reduced alignment accuracy
Solution Approach 1:
A shielding plate made of nickel-iron alloy is introduced as an intermediary component between the permanent magnets and the electron beam path. This shielding plate absorbs and redirects stray magnetic fields, preventing them from deflecting the electron beams while allowing the permanent magnets to maintain their beam condensation and focusing functions.
Solution Approach 2:
The patent changes the magnetic field parameters by introducing a nickel-iron alloy shielding plate with specific thickness (0.5mm to 2mm) and material properties. This alters the magnetic field distribution, reducing stray fields in the radial direction by more than 75% while maintaining the necessary field strength for beam condensation and focusing.
2Manufacturing precision
If shielding plates are added to reduce stray magnetic fields, then beam alignment accuracy is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The shielding plate serves multiple functions simultaneously: it shields against stray magnetic fields, structurally supports the permanent magnet array, and provides a mounting platform for alignment adjustments. This multi-functionality reduces the need for additional separate components, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent employs a nickel-iron alloy composite material for the shielding plate, which combines the magnetic shielding properties of nickel with the structural strength and machinability of iron. This composite material achieves effective stray field reduction while maintaining manufacturability and reasonable cost, avoiding the need for more complex alternative solutions.
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
The shielding plate system effectively reduces stray magnetic fields by more than 75%, enhancing beam alignment and inspection accuracy, thereby reducing the time to detect and fix yield issues in semiconductor manufacturing.
Implementation Method 1
a first permanent magnet array configured to condense the electrons from each electron source into an array of electron beams
Implementation Method 2
The plurality of shielding plates reduce stray magnetic field in a radial direction of the array of electron beams
Implementation Method 3
a second permanent magnet array configured to focus the array of electron beams toward a target on the stage
Data Source
AI summary
The present disclosure provides an inspection system and a method of stray field mitigation. The system includes an array of electron beam columns, a first permanent magnet array, and a plurality of shielding plates. The array of electron beam columns each includes an electron source configured to emit electrons toward a stage. The first permanent magnet array is configured to condense the electrons from each electron source into an array of electron beams. The first permanent magnet array is arranged at a first end of the array of electron beam columns. The plurality of shielding plates extend across the array electron beam columns downstream of the first permanent magnet array in a direction of electron emission. The array of electron beams pass through a plurality of apertures in each of the plurality of shielding plates, which reduces stray magnetic field in a radial direction of the array of electron beams.