Projection Lens Array for Multi-Beamlet Lithography
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Solution Overview
Problem
Current charged particle multi-beamlet systems face challenges in achieving high resolution and throughput due to limitations in spot size, point spread function, and the number of beamlets that can be effectively managed within the physical constraints of the projection optics, leading to issues with aberrations and complexity.
Innovation Solution
The system employs array manipulators, such as group deflector arrays and condenser lens arrays, to converge groups of beamlets towards a single projection lens, avoiding common cross-overs and allowing for a significant increase in the number of beamlets without extreme miniaturization, thereby maintaining exposure latitude and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a common cross-over is used to focus and demagnify all beamlets together, then the system complexity is reduced, but resolution is degraded due to interactions between charged particles
Solution Approach 1:
The patent divides the beamlet paths into separate groups, each with its own focus demagnification system, eliminating the common cross-over. This segmentation allows each group to be focused independently without particle interactions, thereby maintaining high resolution while managing complexity through modular architecture.
2Manufacturing precision
If multiple lenses are provided for controlling each beamlet individually, then resolution is improved, but system complexity and volume increase
Solution Approach 1:
The patent merges multiple beamlets into groups that share common focus demagnification systems. By combining the control of multiple beamlets under fewer lenses rather than providing individual lenses for each beamlet, the system achieves the necessary resolution through grouped control while significantly reducing overall system complexity and volume.
3Productivity
If the number of beamlets is increased to improve throughput, then productivity is improved, but aberrations and alignment errors increase
Solution Approach 1:
By segmenting beamlets into groups with separate focus demagnification systems, the patent enables increased total beamlet count for improved throughput while maintaining alignment accuracy. Each group's independent optical path prevents cumulative aberrations and alignment errors that would occur in a single common path system.
4Manufacturing precision
If spot size is reduced to achieve smaller critical dimensions, then manufacturing precision is improved, but current per beamlet decreases
Solution Approach 1:
The patent combines multiple beamlets into groups that are focused and demagnified together by shared optical systems. This merging allows the system to achieve smaller critical dimensions through reduced spot size while compensating for decreased current per individual beamlet by delivering multiple beamlets to adjacent locations, thereby maintaining sufficient total current for productive lithography.
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 approach enables the achievement of smaller critical dimensions, such as 22 nm, while maintaining sufficient wafer throughput, by reducing spot size and increasing current, and reduces aberrations, simplifying the system's design and operation.
Implementation Method 1
at least one charged particle source for generating a charged particle beam
Implementation Method 2
an aperture array defining separate beamlets or sub-beams from the generated beam
Implementation Method 3
a condenser lens array for focusing the sub-beams
Implementation Method 4
condenser lens array for focusing the sub-beams
Implementation Method 5
an array of projection lens systems for projecting beamlets on to the surface of the target
Implementation Method 6
projection lens systems for projecting beamlets on to the surface of the target
Data Source
AI summary
The invention relates to a charged particle multi-beamlet lithographic system for exposing a target using a plurality of beamlets. The system comprises a beamlet generator for generating a plurality of beamlets, a beamlet blanker for controllably blanking beamlets, and an array of projection lens systems for projecting unblanked beamlets on to the surface of the target. The beamlet generator comprises at least one charged particle source for generating a charged particle beam, a sub-beam generator for defining a plurality of sub-beams from the charged particle beam, a sub-beam manipulator array for influencing the sub-beams, and an aperture array for defining beamlets from the sub-beams.