Multiple-Beam Irradiation Timing to Reduce Coulomb Writing Errors
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Solution Overview
Problem
The Coulomb effect, which causes positional and focus deviations due to electron beam repulsion, becomes significant in multiple-beam writing systems, particularly at high beam current densities, leading to reduced writing accuracy.
Innovation Solution
The multiple charged particle beam writing apparatus classifies beams into two groups: simultaneous on-beams and simultaneous off-beams, controlling their irradiation times to reduce the average on-beam current and mitigate the Coulomb effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the total beam current amount is increased to improve throughput in multiple-beam writing, then productivity is improved, but writing accuracy deteriorates due to the Coulomb effect
Solution Approach 1:
The patent segments the multiple beams into two distinct groups: simultaneous on-beams and simultaneous off-beams. This segmentation allows independent control of beam current distribution over time, enabling the system to maintain high total beam current for improved throughput while reducing the instantaneous current density that causes Coulomb effect, thus preserving writing accuracy.
Solution Approach 2:
The patent implements periodic switching between simultaneous on-beams and simultaneous off-beams within each shot cycle. This periodic action creates time-varying beam current patterns that reduce average current density at any given location, mitigating Coulomb effect while maintaining high overall productivity through efficient use of multiple beams.
2Manufacturing precision
If measures are taken to reduce the total amount of on-beam current to mitigate Coulomb effect, then writing accuracy is improved, but productivity decreases when beam OFF time is longer than beam ON time
Solution Approach 1:
The patent dynamically adjusts the timing and grouping of beam activation within each shot cycle. By making the beam current distribution time-dependent and adaptable, the system can optimize the balance between reducing Coulomb effect (by lowering instantaneous current density) and maintaining productivity (by ensuring sufficient beam ON time), unlike static current reduction approaches.
3Manufacturing precision
If exposure processes are divided into multiple processes with dispersed beam ON intervals to reduce current variation, then writing accuracy is improved, but data transfer volume to blanking plate increases
Solution Approach 1:
The patent merges the control of multiple beams into two grouped control patterns (simultaneous on-beams and simultaneous off-beams) within each shot cycle. This merging approach maintains the benefits of current variation reduction for writing accuracy while significantly reducing data transfer volume compared to individually controlling each beam's timing, as the grouped pattern requires less data than exhaustive individual beam control.
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 effectively reduces the influence of the Coulomb effect, thereby improving writing accuracy without increasing data transfer volume to the blanking plate.
Implementation Method 1
the Coulomb effect, which causes positional and focus deviations due to electron beam repulsion, becomes significant in multiple-beam writing systems, particularly at high beam current densities
Data Source
AI summary
In one embodiment, a multiple charged particle beam writing apparatus includes an emitter configured to emit multiple-beam of charged particles, and an irradiation time controller configured to control an irradiation time of each of a plurality of beams included in the multiple-beam. The plurality of beams are classified into a plurality of groups including a first group and a second group. The irradiation time controller controls beams in the first group to be ON simultaneously at a first timing, and to be OFF after lapse of an irradiation time of each beam, and controls beams in the second group to be ON based on the irradiation time of each beam, and to be OFF simultaneously at a second timing.