Dual-Magnetic-Lens Charged Particle Source for High-Current SEM Resolution
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Solution Overview
Problem
Existing charged particle sources, particularly in scanning electron microscopes, face challenges in providing high angular beam current with high spatial resolution and throughput, especially in identifying defects in sub-20 nanometer semiconductor nodes, where conventional optical inspection tools are inadequate and SEMs suffer from reduced detection duration and resolution trade-offs.
Innovation Solution
A charged particle source with a unique magnetic field distribution, utilizing dual magnetic lenses to minimize the magnetic field at the emitter tip and maximize it along the optical axis, allowing for high beam current and resolution, and enabling operation in both high-resolution and high-throughput modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical inspection tools are used for semiconductor inspection, then the inspection process is fast and non-destructive, but the resolution is insufficient for sub-20 nanometer nodes
Solution Approach 1:
The patent replaces optical inspection systems with an electron beam-based inspection system. The electron source generates a focused electron beam that interacts with the semiconductor wafer, producing signals that reveal defect information. This substitution enables sub-20 nanometer resolution while maintaining high inspection throughput through optimized beam control and detection systems.
2Productivity
If ebeam inspection tools use high beam current for large throughput, then productivity increases, but resolution decreases due to geometric aberration
Solution Approach 1:
The patent divides the electron optical system into multiple functional components: a field emission electron source, condenser lenses, an objective lens, and detection systems. Each component is optimized independently to contribute to both high beam current and high resolution. The segmented approach allows the system to achieve large throughput through high beam current while maintaining sub-20 nanometer resolution through precise optical control.
Solution Approach 2:
The patent employs dynamic control of the electron beam parameters including variable beam current, adjustable focal length of lenses, and real-time optimization of optical conditions. This dynamic adjustment allows the system to operate at high beam current for throughput while maintaining resolution through active compensation of geometric aberrations.
3Measurement precision
If ebeam inspection tools use low beam current for high resolution, then measurement precision improves, but productivity decreases
Solution Approach 1:
The patent utilizes field emission electron sources that enable operation across a wide range of beam current parameters while maintaining stable emission characteristics. By optimizing the interaction between the electron beam and wafer at controlled current levels, the system achieves high resolution inspection with sufficient beam current to maintain practical inspection throughput.
4Quantity of substance
If the magnetic field is maximum at the emitter tip to increase beam current, then beam current increases, but geometric aberration and resolution deteriorate
Solution Approach 1:
The patent implements different magnetic field strengths at different locations within the electron optical system. The field emission source region has optimized magnetic field characteristics for high current extraction, while the beam propagation and focal regions have different field configurations to minimize geometric aberration. This local optimization allows high beam current at the source while maintaining resolution in the focal plane.
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 solution provides a charged particle source capable of delivering large beam current with high resolution, enhancing defect identification efficiency in semiconductor manufacturing processes, particularly in SEMs, by minimizing aberrations and maintaining a small virtual source area.
Implementation Method 1
a magnetic field distribution that is minimum or zero at the emitter tip and maximum along the optical axis
Implementation Method 2
charged particle source with a magnetic field distribution that is minimum or zero at the emitter tip and maximum along the optical axis
Data Source
AI summary
This invention provides a charged particle source, which comprises an emitter and means fo generating a magnetic field distribution. The magnetic field distribution is minimum, about zero, or preferred zero at the tip of the emitter, and along the optical axis is maximum away from the tip immediately. In a preferred embodiment, the magnetic field distribution is provided by dual magnetic lens which provides an anti-symmetric magnetic field at the tip, such that magnetic field at the tip is zero.