Multi-Beam Lithography Overlap Margin Pixel Segmentation
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Solution Overview
Problem
Multi-beam lithography systems face challenges with imaging errors and butting errors due to metrology inaccuracies, leading to unexposed or double-exposed areas, which are exacerbated by the limitations of gray scale methods and data rate constraints in PML2 setups.
Innovation Solution
The method involves creating overlap margins between exposure stripes, where pixels are exposed differently in each stripe, allowing for partial exposure in overlap regions to maintain pattern continuity and reduce the impact of butting errors, without requiring additional complexity in the APS system or affecting gray values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If overlap margins are used between adjacent exposure stripes, then pattern continuity is improved and butting errors are reduced, but the exposure time and data rate requirements increase
Solution Approach 1:
The patent divides the exposure area into multiple stripes with overlap margins, and further segments the pixels within overlap regions into different subsets for different stripes. This segmentation allows parallel processing of different stripe segments, maintaining pattern continuity while managing exposure time through parallel beam exposure.
Solution Approach 2:
The patent performs preliminary planning of pixel subset assignments for overlap regions before actual exposure. By pre-determining which pixels belong to which stripe subsets, the system prepares the exposure pattern in advance, reducing real-time processing requirements and managing data rate constraints.
2Manufacturing precision
If gray scale methods are used to handle overlap regions, then pattern continuity can be maintained, but data rate constraints and system complexity increase
Solution Approach 1:
The patent extracts the overlap region handling from the general gray scale methodology. Instead of using continuous gray scale modulation for all overlap regions, it separates overlap region pixels into discrete subsets that are exposed by specific stripes, simplifying the APS control logic while maintaining pattern continuity.
Solution Approach 2:
The patent applies different exposure strategies to different regions: full exposure for non-overlap pixels and selective subset exposure for overlap pixels. This local differentiation maintains pattern continuity in overlap regions without requiring complex gray scale modulation across the entire exposure field, reducing overall system complexity.
3Manufacturing precision
If multiple beamlets expose the same pixel in overlap regions, then pattern continuity is improved, but the risk of double exposure and butting errors increases
Solution Approach 1:
The patent assigns different exposure responsibilities to different beamlets in overlap regions through pixel subset differentiation. Each stripe exposes only its assigned subset of pixels in the overlap region, ensuring that every pixel receives exactly one exposure while maintaining pattern continuity across stripe boundaries.
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 minimizes the impact of butting errors by generating a pattern that is intermediate between the component patterns, reducing abrupt offsets and maintaining pattern continuity, while preserving gray levels for adjustments and avoiding the need for dose modulation.
Implementation Method 1
A method for multi-beam exposure on a target with a particle beam is provided
Implementation Method 2
each overlap margin in a stripe is brought into spatial overlap with a corresponding overlap margin of an adjacent stripe
Data Source
AI summary
For irradiating a target with a beam of energetic electrically charged particles comprising a plurality of beamlets, the target is exposed in a sequence of exposure stripes composed image pixels. These stripes (s1, s2) are, at their boundaries to adjacent stripes, provided with overlap margins (m12, m21) which are mutually overlapped, so nominal positions of image pixels in the overlap margin (m21) overlap, or substantially coincide, with image pixels in the corresponding overlap margin (m12). During the exposure of an overlap margin (m21), a first subset (n1) of image pixels in said overlap margin are exposed while those of a second subset (n2), possibly a complementary subset with respect to a desired pattern, are not exposed; contrariwise, during the exposure of the corresponding overlap margin (m12), image pixels corresponding to image pixels in the first subset are not exposed, but those corresponding to image pixels in the second subset are.