Aberration-Corrected Multibeam Source for High-Resolution Inspection
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Solution Overview
Problem
Current charged particle beam devices face limitations in throughput and resolution due to off-axial aberrations, such as field astigmatism, coma, and distortion, which hinder efficient inspection of semiconductor wafers and masks, especially at the 20 nm node and beyond.
Innovation Solution
A charged particle beam device with a multi-aperture plate generating an array of primary beamlets and an aberration correction element, comprising multipole elements, is used to correct spherical and chromatic aberrations, allowing for focused beamlets to be directed onto separate locations on the specimen, improving resolution uniformity.
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 is achieved, but inspection throughput is too slow
Solution Approach 1:
The patent divides a single electron beam into multiple parallel beamlets using an aperture array, enabling simultaneous inspection of multiple locations on the wafer surface. This segmentation allows the system to maintain high resolution while dramatically increasing throughput by inspecting multiple points in parallel rather than scanning sequentially with a single beam.
2Productivity
If multiple beamlets are generated to increase throughput, then inspection speed improves, but off-axial aberrations (field astigmatism, coma, distortion) increase
Solution Approach 1:
The patent applies field curvature correction electrodes that create position-dependent field distributions to compensate for off-axial aberrations. Each beamlet experiences locally optimized field conditions tailored to its specific position in the aperture array, correcting field astigmatism, coma, and distortion while maintaining resolution uniformity across all beamlets.
Solution Approach 2:
The patent dynamically adjusts electric field parameters using correction electrodes to compensate for aberrations. By changing field strength and distribution parameters based on beamlet position, the system maintains consistent resolution across the aperture array while enabling multiple beamlets for high throughput inspection.
3Measurement precision
If the total emission angle from the source is limited to reduce off-axial aberrations, then resolution uniformity improves, but the number of total beamlets is reduced
Solution Approach 1:
The patent changes the electric field parameters using correction electrodes to compensate for aberrations, enabling the system to use a larger total emission angle without sacrificing resolution uniformity. This allows more beamlets to be generated while maintaining consistent resolution across the aperture array.
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 enhances the resolution and throughput of charged particle beam inspection by correcting aberrations, ensuring uniformity and efficiency in detecting defects on semiconductor wafers and masks, particularly at the nanoscale.
Implementation Method 1
a charged particle beam source to generate a primary charged particle beam
Implementation Method 2
a multi-aperture plate having at least two openings to generate an array of charged particle beamlets
Implementation Method 3
an objective lens assembly for focusing each primary charged particle beamlet of the array of primary charged particle beamlets onto a separate location on the specimen
Implementation Method 4
an aberration correction element to correct at least one of spherical aberrations and chromatic aberrations of rotational symmetric charged particle lenses; the aberration correction element provided between the charged particle beam source and the multi-aperture plate to correct a difference of the first resolution on the specimen as compared to the second resolution on the specimen, comprising at least two multipole elements with 6 or more poles
Data Source
AI summary
A charged particle beam device for inspection of a specimen with an array of primary charged particle beamlets is described. The charged particle beam device includes a charged particle beam source to generate a primary charged particle beam; a multi-aperture plate having at least two openings to generate an array of charged particle beamlets having at least a first beamlet having a first resolution on the specimen and a second beamlet having a second resolution on the specimen; an aberration correction element to correct at least one of spherical aberrations and chromatic aberrations of rotational symmetric charged particle lenses; and an objective lens assembly for focusing each primary charged particle beamlet of the array of primary charged particle beamlets onto a separate location on the specimen.