Tilt-Column Multi-Beam Electron Optics for Beamlet Aberration Control
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Solution Overview
Problem
Existing electron beam imaging systems face challenges with nonuniformity, astigmatism, and field curvature in multiple beamlets generated from a single electron source, which become increasingly difficult to correct as the number of beamlets increases, leading to reduced resolution and throughput in semiconductor inspection processes.
Innovation Solution
A tilt-column electron beam imaging system utilizing multiple electron beam sources and tilted illumination columns, where each beamlet passes through a common crossover volume, allowing for independent adjustment of beamlets using electron optics to correct for astigmatism and field curvature, and reducing heat accumulation and cross-talk between beamlets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electron source is used to generate multiple beamlets, then the device complexity is reduced, but the manufacturing precision deteriorates due to nonuniformity, astigmatism, and field curvature across beamlets
Solution Approach 1:
The system divides the electron beam generation into multiple independent sources, with each source producing a single beamlet. This segmentation eliminates the nonuniformity and distortion problems that occur when trying to create multiple beamlets from a single source, as each beamlet is generated independently with consistent optical properties.
Solution Approach 2:
The patent introduces an intermediary optical system that includes a condenser lens and illumination optics positioned between the electron sources and the sample. This intermediary system provides common illumination conditions to all beamlets, ensuring uniformity in beamlet properties while allowing each source to operate independently.
2Productivity
If the number of beamlets is increased to improve productivity, then the throughput increases, but the manufacturing precision deteriorates due to increased difficulty in correcting astigmatism and field curvature
Solution Approach 1:
By assigning one electron source per beamlet, the system can scale the number of beamlets simply by adding more independent sources. Each source-illumination-column assembly operates independently, so increasing the number of beamlets does not increase the complexity of correcting optical aberrations, as each beamlet can be corrected using the same standardized illumination optics.
Solution Approach 2:
The illumination optics and condenser lens are designed as universal components that can serve multiple beamlets simultaneously. Each illumination column can be replicated and configured to work with any beamlet, providing a standardized solution for correcting astigmatism and field curvature that scales easily with the number of beamlets.
3Manufacturing precision
If multiple electron sources are used with tilted illumination columns, then the manufacturing precision is improved through independent beamlet adjustment, but the device complexity increases
Solution Approach 1:
The illumination columns are tilted at specific angles relative to the electron beam sources, creating an asymmetric configuration. This tilt allows the illumination optics to access the beamlets from an optimal angle, enabling effective correction of astigmatism and field curvature while maintaining a compact overall system layout.
Solution Approach 2:
The system uses tilted illumination columns that introduce a spatial dimension to the beam adjustment capability. By tilting the illumination columns, the system can correct optical aberrations without requiring additional adjustment mechanisms in the traditional axial direction, effectively using spatial orientation to achieve precise beam control.
4Productivity
If beamlets are closely spaced to probe multiple regions simultaneously, then the productivity increases, but the object-generated harmful factors worsen due to heat accumulation and cross-talk between beamlets
Solution Approach 1:
Each electron source and its associated illumination column form an independent, segmented unit that probes a specific region. This segmentation allows beamlets to be closely spaced on the sample while maintaining independent thermal zones, as each source can be independently controlled and cooled, preventing heat accumulation from affecting adjacent beamlets.
Solution Approach 2:
The system can operate beamlets in a periodic or pulsed manner, where not all beamlets are active simultaneously. This periodic operation allows thermal dissipation between activation cycles, reducing heat accumulation and cross-talk effects while still achieving high overall throughput through coordinated activation of multiple beamlets.
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 system achieves improved resolution uniformity and throughput by allowing independent correction of beamlets, reducing thermal issues and cross-talk, and enabling simultaneous probing of multiple regions on a sample with reduced distortion and astigmatism.
Implementation Method 1
a plurality of electron beam sources configured to generate a plurality of beamlets
Implementation Method 2
a set of one or more electron optics configured to adjust the respective beamlet
Implementation Method 3
each of the plurality of beamlets pass through a first common crossover volume
Implementation Method 4
a first tilt axis of a first tilt-illumination column may be orientated along a first angle and at least one additional tilt axis of at least one additional tilt-illumination column may be orientated along at least one additional angle different from the first angle
Implementation Method 5
collecting secondary electrons emanating from the plurality of measurement regions of the sample utilizing a detector
Data Source
AI summary
A system and method of a tilt-column electron beam imaging system is disclosed. The system may include an imaging sub-system. The imaging sub-system may include a plurality of electron beam sources configured to generate a plurality of beamlets. The imaging sub-system may further include a plurality of tilt-illumination columns, where a respective tilt-illumination column is configured to receive a respective beamlet from a respective electron beam source. For the system and method, a first tilt axis of a first tilt-illumination column may be orientated along a first angle and at least one additional tilt axis of at least one additional tilt-illumination column may be orientated along at least one additional angle different from the first angle, where each of the plurality of beamlets pass through a first common crossover volume.