Multi-Beam Electron Optics for Field Curvature Correction
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Solution Overview
Problem
Conventional single-beam scanning electron microscopes are inefficient for inspecting semiconductor wafers due to slow scanning times, limiting throughput and resolution, especially as defect sizes shrink beyond the 20 nm node.
Innovation Solution
A charged particle multi-beam device generates an array of primary charged particle beamlets with a multi-aperture lens plate and electrical field correction electrodes, allowing for high-resolution inspection with improved throughput by compensating field curvature and sample tilt effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single finely focused electron beam is used to scan the wafer surface, then high resolution inspection is achieved, but the inspection time becomes too long and throughput is limited
Solution Approach 1:
The patent divides a single electron beam into multiple parallel beamlets using a multi-aperture plate. This segmentation allows simultaneous inspection of multiple locations on the wafer surface, maintaining high resolution at each beamlet while collectively covering the entire wafer area much faster than a single beam could achieve.
2Measurement precision
If the entire wafer area is inspected with high resolution, then all defects are detected, but the inspection process takes too long for production requirements
Solution Approach 1:
By segmenting the electron beam into multiple parallel beamlets that can be simultaneously scanned across the wafer, the system maintains high-resolution defect detection capability while reducing total inspection time through parallel processing of multiple wafer regions.
Solution Approach 2:
The multi-beam system enables continuous high-resolution inspection across the entire wafer surface by maintaining multiple active beamlets operating simultaneously throughout the scan, eliminating idle time between sequential single-beam inspections of different areas.
3Device complexity
If conventional single-beam SEM is used for wafer inspection, then equipment complexity is low, but it cannot meet the resolution and throughput requirements for modern semiconductor manufacturing
Solution Approach 1:
The introduction of a multi-aperture plate to create multiple beamlets adds controlled complexity to the system, enabling simultaneous high-resolution inspection across the entire wafer surface, which meets modern semiconductor manufacturing requirements while maintaining manageable system architecture.
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 enables fast and precise inspection of semiconductor wafers with spot sizes less than 20 nm, increasing imaging quality and throughput by correcting field curvature and sample tilt, thus addressing the limitations of single-beam systems.
Implementation Method 1
a charged particle beam source (110) including a particle beam emitter (111) is provided, which generates an array of primary charged particle beamlets (15)
Implementation Method 2
a multi-aperture lens plate (113) is provided, with a plurality of aperture openings, for generating the array of primary charged particle beamlets (15)
Implementation Method 3
the array of primary charged particle beamlets (15) is focused with an objective lens (130) on separate locations on a specimen (140)
Implementation Method 4
a first electrode (112) is provided, which is adapted to be driven for generating an electrical field on a surface of the multi-aperture lens plate (113)
Implementation Method 5
a component in z-direction of the electrical field provided by the first electrode (112) is non-rotational symmetric on a surface of the multi-aperture lens plate (113)
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A method for inspecting a specimen with an array of primary charged particle beamlets in a charged particle beam device having an optical axis. The method includes generating a primary charged particle beam; illuminating a multi-aperture lens plate with the primary charged particle beam to generate the array of primary charged particle beamlets; and correcting a field curvature of the charged particle beam device with a first and a second field curvature correction electrode. The method further includes applying a voltage to the first and to the second field curvature correction electrode. At least one of the field strength provided by the first and the second field curvature correction electrode varies in a plane perpendicular to the optical axis of the charged particle beam device. The method further includes focusing the primary charged particle beamlets on separate locations on the specimen with an objective lens.