Lithographic Aberration Correction via Frequency-Filtered Signal Analysis
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Solution Overview
Problem
Lithographic apparatuses experience aberrations in the projected image due to the projection system and mask distortions, which current methods fail to adequately mitigate, affecting the accuracy of pattern transfer onto substrates.
Innovation Solution
A method that measures aberrations to obtain a signal with distinct frequency components, calculates a correction based on the high-frequency component, and applies it to the lithographic apparatus by manipulating its lenses, thereby reducing aberrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the projection system images the pattern onto the substrate, then the pattern transfer is achieved, but aberrations are introduced in the projected image
Solution Approach 1:
The patent applies preliminary action by measuring aberrations and calculating corrections before the actual pattern exposure. The system measures aberrations using test patterns, computes correction values, and stores them for application during subsequent production exposures, thereby preemptively addressing aberration issues.
Solution Approach 2:
The patent implements feedback by measuring aberrations in the projected image and using these measurements to calculate and apply corrections. The system continuously monitors aberration levels and adjusts correction parameters based on measured deviations, creating a closed-loop control system that reduces aberrations.
2Manufacturing precision
If aberration measurement and correction are performed, then aberration reduction is achieved, but measurement and processing time are required
Solution Approach 1:
The patent performs aberration measurements and correction calculations in advance during a calibration phase before production begins. By completing the time-consuming measurement and processing steps beforehand, the system minimizes time loss during actual substrate exposure while maintaining high correction accuracy.
Solution Approach 2:
The patent employs periodic action by performing aberration measurements at regular intervals or at specific milestones during substrate exposure. This allows the system to maintain accurate corrections without requiring continuous measurement, thereby balancing precision with time efficiency.
Data Source
AI summary
A method of reducing an aberration arising during operation of a lithographic apparatus, the method comprising measuring the aberration to obtain an aberration signal, the aberration signal comprising a first component and a second component, wherein the first component of the aberration signal comprises a first frequency band and the second component of the aberration signal comprises a second frequency band, wherein the first frequency band comprises frequencies that are higher than frequencies comprised in the second frequency band, calculating a correction, wherein a first part of the correction is calculated based on the first component of the aberration signal, and applying the correction to the lithographic apparatus.