Exposure Apparatus Encoder System Air Fluctuation Mitigation

The patent introduces an encoder scale as an intermediary element between the measurement system and the substrate. The encoder scale serves as a stable reference that mediates the position measurement, allowing the system to obtain accurate substrate position information without being directly affected by air fluctuation. The scale acts as a physical intermediary that translates substrate position into measurable signals while being immune to atmospheric disturbances.

The patent replaces the optical interferometer system with a mechanical encoder system. Instead of using optical beams that are susceptible to air fluctuation, the invention employs a mechanical encoder scale with reading heads that physically track substrate position. This substitution eliminates the harmful effect of air fluctuation by transitioning from an optical measurement mechanism to a mechanical one that is inherently more stable in atmospheric conditions.

The patent divides the encoder system into multiple segments: multiple encoder scales are arranged along the substrate movement direction, and multiple reading heads are positioned to read from different scales simultaneously or sequentially. This segmentation allows the system to cover the entire movement range of large substrates while maintaining measurement stability, as each scale segment provides reliable local measurements that are combined to achieve global position coverage.

The patent extends the encoder system from a single linear dimension to a two-dimensional arrangement by placing multiple scales and reading heads in both the scanning direction and the width direction. This dimensional expansion allows the system to cover large substrate areas comprehensively, with scales arranged to provide overlapping or continuous coverage across the entire substrate movement range while maintaining the stability benefits of the encoder mechanism.

The patent segments the measurement system into multiple independent encoder scales and reading heads distributed across the large substrate area. This segmentation allows each local measurement point to maintain high precision by being close to the substrate surface and reading from a nearby scale, while the collective system covers the entire large substrate. The segmented approach enables large substrate processing without sacrificing positioning accuracy, as each segment operates independently with minimal exposure to air fluctuation.

The patent implements local quality by ensuring that each reading head is positioned close to the substrate surface and reads from a locally adjacent encoder scale. This local configuration minimizes the optical or mechanical path length through air, reducing the impact of air fluctuation on each local measurement. By optimizing the local measurement quality at each position across the large substrate, the system maintains high positioning accuracy throughout the entire substrate area while supporting increased substrate size and productivity.