Multi-Beam Writer Exposure Slot Duration Adaptation
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Solution Overview
Problem
Current charged particle lithography systems do not adequately account for small fluctuations in source current and varying target doses, leading to inconsistencies in critical dimension uniformity and exposure dose across the substrate.
Innovation Solution
Adapting the duration of exposure slots by determining a desired effective pixel exposure time and calculating contributing exposure slot durations to compensate for fluctuations, using a set of allowed durations with incremental adjustments, and monitoring particle beam intensity to inversely scale the exposure time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fixed duration exposure slots are used in multi-beam writers, then the writing process is simple and fast, but source current fluctuations cause exposure dose variations and poor critical dimension uniformity
Solution Approach 1:
The patent implements dynamic adjustment of exposure slot durations based on monitored source current fluctuations. The system continuously adapts the exposure time for each slot to compensate for variations in particle beam intensity, transforming a static exposure process into a dynamic one that maintains consistent exposure doses despite source instability.
Solution Approach 2:
The system changes the exposure time parameter in response to detected source current variations. By adjusting the duration of exposure slots according to actual beam intensity conditions, the patent maintains uniform exposure doses across the substrate, directly addressing the critical dimension uniformity problem.
2Manufacturing precision
If uniform exposure slot durations are applied to all pixels, then the control process is simple, but variations in source current lead to non-uniform exposure doses across the substrate
Solution Approach 1:
The patent incorporates a feedback mechanism where source current is monitored in real-time and this information feeds back to adjust exposure slot durations. This closed-loop control system automatically compensates for source variations, maintaining uniform exposure doses without requiring complex manual intervention.
Solution Approach 2:
The system performs self-adjustment by automatically modifying exposure parameters based on its own monitored performance. The multi-beam writer detects its own source current fluctuations and independently corrects exposure doses, eliminating the need for external calibration or complex operator intervention.
3Reliability
If the duration of each exposure slot is adapted based on source current fluctuations, then exposure dose uniformity improves, but the control and calculation complexity increases
Solution Approach 1:
The system performs preliminary monitoring of source current characteristics and pre-calculates appropriate exposure slot durations before actual exposure begins. This advance preparation allows the system to establish a compensation strategy that ensures dose consistency without adding complexity during the actual writing process.
Data Source
AI summary
In a charged-particle lithography apparatus, during writing a desired pattern, the duration of exposure slots is adapted to compensate for fluctuations of the particle beam. In the writing process the aperture images are mutually overlapping on the target so each pixel is exposed through a number of aperture images overlapping at the respective pixel, which results in an exposure of the respective pixel through an effective pixel exposure time, i.e., the sum of durations of contributing exposure slots, and the exposure slot durations are adjusted by:(i) determining a desired duration of the effective pixel exposure time for the pixels, as a function of the time of exposure of the pixels,(ii) determining contributing exposure slots for the pixels,(iii) calculating durations for the contributing exposure slots thus determined such that the sum of the durations over said contributing exposure slots is an actual effective exposure time which approximates said desired duration of the effective pixel exposure time.The durations in step (iii) are calculated in accordance with a predetermined set of allowed durations, wherein at least one of the durations thus calculated is different from the other durations selected for said set of exposure slots.