Beamlet Position Determination in Multi-Beamlet Lithography
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Solution Overview
Problem
Current multi-beamlet lithography systems face challenges in accurately determining the position of charged particle beamlets due to manufacturing tolerances and thermal drift, leading to errors in patterning, especially when beamlet sizes are smaller than feature sizes, which affects throughput and resolution.
Innovation Solution
A method using a sensor with a conversion element and a light-sensitive detector to measure beamlet positions by exposing features on a two-dimensional pattern of blocking and non-blocking regions, allowing for flexible design and improved accuracy by creating a two-dimensional image of light intensity values across a grid, enabling sub-grid cell precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If frequent beamlet position measurement is performed to improve positioning accuracy, then measurement precision is improved, but productivity deteriorates due to reduced throughput
Solution Approach 1:
The patent performs beamlet position measurements during the exposure process itself, utilizing the exposure features as measurement targets. This preliminary action integrates positioning and exposure operations, allowing position calibration to occur before final patterning without requiring separate measurement steps that would reduce throughput.
Solution Approach 2:
The exposure features serve dual purposes: they function as both the pattern to be written on the target surface and as reference markers for beamlet position measurement. This multi-functionality eliminates the need for separate measurement features, allowing simultaneous achievement of patterning and position calibration without sacrificing throughput.
2Manufacturing precision
If beamlet size is reduced to improve resolution, then manufacturing precision is improved, but measurement precision deteriorates when beamlet size is smaller than feature size
Solution Approach 1:
The patent introduces exposure features as intermediary objects that mediate between the small beamlet and the measurement system. These features are larger than the beamlet size, providing sufficient contrast and detectability for accurate position measurement while the beamlet itself maintains its small size for high-resolution patterning.
Solution Approach 2:
The patent shifts the measurement approach from directly detecting the beamlet (one-dimensional spot detection) to detecting the interaction between the beamlet and exposure features (two-dimensional pattern formation). This dimensional change allows measurement of beamlet position through the spatial distribution of exposed features rather than direct beamlet imaging.
3Measurement precision
If conventional beamlet position calibration is performed to improve positioning accuracy, then measurement precision is improved, but device complexity increases due to multiple calibration steps
Solution Approach 1:
The patent merges the beamlet position calibration process with the normal exposure operation. By using the exposure features as both the pattern to be written and the reference for position measurement, the calibration function is combined with the exposure function, eliminating separate calibration steps and reducing overall process complexity.
Solution Approach 2:
The exposure features serve themselves dual purposes: they are both the intended pattern output and the reference markers for position calibration. This self-service approach eliminates the need for external calibration features or separate measurement systems, simplifying the overall device architecture and operation.
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 enhances the accuracy of beam separation measurement and position determination, improving patterning precision and throughput while maintaining or increasing measurement efficiency, especially in high-resolution applications like electron beam lithography.
Implementation Method 1
a sensor comprising a conversion element for converting the energy of charged particles into light
Implementation Method 2
a light sensitive detector... converting the received light into a light intensity value
Data Source
AI summary
The invention relates to a method for determining a beamlet position in a charged particle multi-beamlet exposure apparatus. The apparatus is provided with a sensor comprising a conversion clement for converting charged particle energy into light and a light sensitive detector. The conversion element is provided with a sensor surface area provided with a 2D-pattern of beamlet blocking and non-blocking regions. The method comprises taking a plurality of measurements and determining the position of the beamlet with respect to the 2D-pattern on the basis of a 2D-image created by means of the measurements. Each measurement comprises exposing a feature onto a portion of the 2D-pattern with a beamlet, wherein the feature position differs for each measurement, receiving light transmitted through the non-blocking regions, converting the received light into a light intensity value, and assigning the light intensity value to the position at which the measurement was taken.