Multi Beam Deflector Correction for Stitching Accuracy
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Solution Overview
Problem
In multi-beam writing apparatuses for semiconductor devices, the beam shape measurement accuracy is compromised due to increased beam deflection by the main deflector, leading to distortion and reduced stitching accuracy of the written figures.
Innovation Solution
A method and apparatus that corrects the main deflection field using polynomial expressions for beam position shifts, allowing for accurate beam shape measurement by adjusting the main deflector's deflection sensitivity and ensuring uniform beam shape across different apertures, thereby maintaining beam shape integrity during measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the main deflector applies a large amount of beam deflection to scan the reflection mark on the stage, then the beam can cover the entire measurement area, but the beam path changes and the beam shape distorts, decreasing measurement accuracy
Solution Approach 1:
The patent measures the beam shape at the center of the main deflector's deflection field before performing actual writing operations. By conducting this preliminary measurement when the deflection amount is minimal, the system obtains accurate beam shape data without the distortion caused by large deflection angles. This preliminary action ensures that the beam shape characteristics are captured under optimal conditions, which can then be used for subsequent writing processes.
2Productivity
If multiple beams are used to irradiate the substrate simultaneously, then the throughput is greatly improved, but the stitching accuracy of the written figures becomes more sensitive to beam shape variations
Solution Approach 1:
The patent implements a feedback mechanism where the beam shape is measured using the same multiple beams that will be used for writing. The measured beam shapes are then used to calculate correction values for the main deflector's deflection field. This feedback loop ensures that any variations in beam shape are compensated for, maintaining high stitching accuracy even when using multiple beams simultaneously for improved throughput.
Solution Approach 2:
The patent adjusts the deflection field parameters of the main deflector based on the measured beam shapes. By changing the deflection field parameters (such as deflection coefficients) to compensate for beam shape variations, the system maintains consistent beam positioning and shape across all apertures. This parameter adjustment ensures that multiple beams can work together with high precision, preserving stitching accuracy while maintaining the productivity benefits of multi-beam 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 shape measurement and improves the stitching accuracy of the written figures by maintaining beam shape consistency, ensuring precise pattern formation on semiconductor substrates.
Implementation Method 1
a main deflector deflecting beams having been subjected to blanking deflection to a writing position of the beams
Implementation Method 2
a detector scanning a mark on the stage with each of the beams having been deflected by the main deflector and detecting a beam position from a change in intensity of reflected charged particles
Data Source
AI summary
In one embodiment, a multi charged-particle beam writing apparatus includes a plurality of blankers switching between ON and OFF state of a corresponding beam among multiple beams, a main deflector deflecting beams having been subjected to blanking deflection to a writing position of the beams in accordance with movement of a stage, a detector scanning a mark on the stage with each of the beams having been deflected by the main deflector and detecting a beam position from a change in intensity of reflected charged particles and a position of the stage, and a beam shape calculator switching an ON beam, scanning the mark with the ON beam, and calculating a shape of the multiple beams from a beam position. A shape of a deflection field of the main deflector is corrected by using a polynomial representing an amount of beam position shift that is dependent on a beam deflection position of the main deflector and then the mark is scanned with the ON beam. The polynomial is different for each ON beam.