Multi-beam writing dose error reduction via divided shot assignment
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Solution Overview
Problem
Multi-beam writing techniques face errors in dose delivery due to limitations in the aperture diameter of mask holes, leading to inaccuracies in beam current and irradiation dose, making it challenging to reduce dose errors effectively.
Innovation Solution
A method where each unit irradiation region is assigned divided shots from multiple beams, with calculated irradiation times, and the system determines whether to keep each divided shot 'on' or 'off' to achieve a combined irradiation time equivalent to the calculated time, using collective deflection to switch beams and ensure continuous irradiation with optimal beam distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-beam writing is used to increase writing throughput, then productivity is improved, but manufacturing precision deteriorates due to dose errors from aperture diameter limitations
Solution Approach 1:
The patent segments the irradiation process into multiple divided shots for each unit irradiation region. Instead of using a single continuous beam irradiation, the method divides the irradiation into multiple discrete shots, allowing different beams to be assigned to different shots. This segmentation enables the system to overcome the dose accuracy limitations of individual beams while maintaining high throughput through parallel multi-beam operation.
Solution Approach 2:
The patent changes the parameter of irradiation time by dividing it into multiple divided shots with different time allocations. By adjusting the irradiation time of each divided shot and assigning different beams to different shots, the system can compensate for beam current variations and achieve more accurate total dose delivery. This parameter change transforms the fixed dose error problem into a controllable variable through time-based distribution.
2Manufacturing precision
If aperture diameter of mask holes is reduced to improve beam precision, then manufacturing precision is improved, but reliability deteriorates due to processing errors and beam current errors
Solution Approach 1:
The patent segments the total irradiation dose into multiple divided shots, where each shot can be delivered by a different beam. This segmentation allows the system to distribute the dosing task across multiple beams, reducing the reliance on any single beam's precision and current stability. The aperture-induced errors in individual beams are averaged out across multiple shots.
Solution Approach 2:
The patent implements a control mechanism that determines whether to make each divided shot beam 'on' or beam 'off' based on calculated irradiation times and beam assignments. This feedback-controlled switching system monitors and adjusts beam activation to ensure that the cumulative dose from multiple divided shots achieves the target dose accurately, compensating for variations in individual beam performance.
3Manufacturing precision
If divided shots are assigned to multiple beams with beam switching, then manufacturing precision is improved by reducing dose errors, but device complexity increases
Solution Approach 1:
The patent makes the multi-beam system perform multiple functions: individual beams can be assigned to different divided shots, and the same beam can be reused across different shots. The beam switching mechanism serves both the function of selecting which beam irradiates which region and the function of distributing the total dose through time-based control. This multi-functionality reduces the need for additional dedicated components.
Solution Approach 2:
The patent employs a beam switching strategy where beams are turned 'off' for certain divided shots and turned 'on' for others based on assignment calculations. This discarding and recovering of beam activation states allows the system to optimize dose delivery by selectively using available beams, reducing the need for continuous operation of all beams and simplifying the control logic for dose management.
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 reduces dose errors by equalizing beam current variations and improving the accuracy of irradiation, enhancing the precision and efficiency of multi-beam writing processes.
Implementation Method 1
a deflector configured to collectively deflect a plurality of charged particle beams in the multi-beams
Data Source
AI summary
A multi charged particle beam writing method includes assigning, for each unit irradiation region per beam of multi-beams, each divided shot obtained by dividing a shot of a maximum irradiation time and continuously irradiate the same unit irradiation region, to at least one of a plurality of beams that can be switched by collective deflection; calculating, for each unit irradiation region, an irradiation time; determining, for each unit irradiation region, whether to make each divided shot be beam “on” or “off” so that the total irradiation time for a plurality of corresponding divided shots to be beam “on” may become a combination equivalent to the irradiation time calculated; and applying, to the corresponding unit irradiation region, the plurality of corresponding divided shots to be beam “on”, using the plurality of beams while switching a beam between beams by collective deflection.