Multi-beam Exposure Irradiation Time Control via Shot Grouping
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Solution Overview
Problem
In multi-beam writing techniques, the existing blanking control systems face challenges in achieving high-speed and high-precision control of irradiation time due to space and current restrictions on the blanking aperture array substrate, limiting the ability to correct irradiation time errors effectively.
Innovation Solution
A method and apparatus that calculate an effective irradiation time by combining divided shots with pre-acquired blanking error times, generating correlation data to select the optimal combination of divided shots for each irradiation position, and performing exposure using multi-beams based on this selection to achieve the desired irradiation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a blanking control circuit for each beam is placed on the blanking aperture array substrate with high-speed control capability, then irradiation time control precision is improved, but device complexity and space requirements increase
Solution Approach 1:
The irradiation time control is segmented into two parts: coarse control is performed by a simplified blanking control circuit on the substrate using divide-and-conquer shots, while fine control is achieved by selectively combining multiple shot groups. This segmentation allows the substrate circuit to remain simple while achieving high precision through post-processing combination of pre-measured shot groups with different irradiation times.
Solution Approach 2:
Irradiation time correction values are pre-calculated and stored in a lookup table based on measured blanking errors for different shot groups. During actual operation, the system simply retrieves the appropriate correction value from the pre-computed table and combines shot groups accordingly, eliminating the need for complex real-time calculations on the substrate.
2Productivity
If the pitch of multi-beams is narrowed to increase throughput, then productivity is improved, but it becomes more difficult to install blanking control circuits for each beam on the substrate
Solution Approach 1:
The beam array is conceptually segmented into multiple shot groups, each with predetermined irradiation times. By controlling which shot groups are activated rather than controlling irradiation time continuously for each beam, the system achieves precise dose control without requiring complex timing circuits at each beam location, enabling tighter beam pitch.
Solution Approach 2:
A single simplified blanking control circuit structure is designed to handle multiple shot groups with different irradiation time characteristics. This universal circuit design can serve all beams in the array, eliminating the need for customized complex circuits for each beam and allowing higher beam density.
3Manufacturing precision
If divided shots are combined to achieve desired irradiation time, then irradiation time precision is improved, but the number of shots and processing steps increase
Solution Approach 1:
Multiple shot groups with different irradiation times are pre-measured and their correction values are pre-calculated and stored in a lookup table. During actual operation, the system only needs to retrieve the appropriate correction value and select the corresponding shot group combination, transforming a complex real-time control problem into a simple table-lookup operation.
Solution Approach 2:
The complex mechanical/control system of precisely timing each shot's duration is replaced by a digital lookup table system. Instead of using complex timing circuits to achieve precise irradiation times, the system uses pre-computed correction data and selective combination of shot groups, substituting analog timing precision with digital data retrieval and combination logic.
Data Source
AI summary
A multi charged particle beam exposure method includes calculating an effective irradiation time, for each of a plurality of control irradiation time periods for controlling an irradiation time of each beam in the multi-beams of a charged particle beam, using a blanking error time of each divided shot of a plurality of divided shots, previously acquired, due to an error of blanking control for each divided shot; generating correlation data representing a relation between the control irradiation time and the effective irradiation time; selecting, using the correlation data, for each irradiation position of a target object, the combination of the divided shots corresponding to the effective irradiation time to be closer to each desired irradiation time; and performing exposure, using the multi-beams, based on the combination of the divided shots selected for each irradiation position of the target object.