Exposure Apparatus Image Shift Correction via Magnification Control
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Solution Overview
Problem
Existing exposure apparatuses with catadioptric type projection optical systems face issues with image shift and aberration fluctuations when changing projection magnification, leading to reduced throughput due to the need for repeated baseline value measurements.
Innovation Solution
An exposure apparatus with a projection optical system that includes a magnification modification device, a calculation device to determine shift length, and a correction device to adjust the exposure area position, allowing for precise correction of image shift without installing additional optical elements and reducing the need for frequent baseline value measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an optical element for correction is inserted into the optical path to correct image shift, then image shift correction is achieved, but device complexity increases and other aberrations may fluctuate
Solution Approach 1:
The patent replaces the mechanical/optical correction approach (inserting physical optical elements) with a computational approach. The calculation device computes correction values based on the relationship between projection magnification and image shift, then the control device applies these corrections to the exposure apparatus positioning system, eliminating the need for additional optical elements while maintaining correction effectiveness
Solution Approach 2:
The patent changes the approach from physically altering the optical path to changing operational parameters. By calculating correction values based on projection magnification parameters and applying them to the exposure positioning system, the patent achieves image shift correction through parameter adjustment rather than physical modification
2Measurement precision
If baseline value measurement is performed each time projection magnification is changed, then measurement accuracy is maintained, but throughput decreases sharply
Solution Approach 1:
The patent performs baseline value measurement only once initially, then pre-calculates correction values for various projection magnification changes. This preliminary action eliminates the need for repeated measurements, maintaining measurement accuracy while preventing throughput degradation
Solution Approach 2:
The patent creates a computational model that copies the relationship between projection magnification and image shift. Once the baseline is established, the calculation device uses this model to predict correction values for different magnification settings without requiring physical remeasurement, thus maintaining accuracy while improving throughput
3Adaptability or versatility
If the center of the optical axis is set at a different position from the center of the exposure area, then adaptability for various exposure areas is improved, but image shift occurs when projection magnification is changed
Solution Approach 1:
The patent implements a feedback mechanism where the calculation device continuously computes correction values based on the current projection magnification and the known relationship between magnification and image shift. The control device then applies these feedback corrections to the exposure positioning system, maintaining manufacturing precision while preserving the adaptability benefits of offset optical axis positioning
Data Source
AI summary
An exposure apparatus includes a projection optical system, which projects a pattern of a mask onto a prescribed exposure area on a substrate at a prescribed projection magnification. The optical axis center of the projection optical system is set to a position different from that of the center of the projection area onto which the pattern is projected. The exposure apparatus further includes a magnification modification device, which modifies the projection magnification of the projection optical system; a calculation device, which calculates a shift length of the center of the projection area associated with modification of the projection magnification; and a correction device, which corrects the position information of the exposure area based on the shift length of the center of the projection area.