Fluid Gauge With Multiple Reference Gaps For Wafer Positioning

The single reference gap is segmented into multiple reference gaps (first reference gap, second reference gap, etc.) with different spacings. Each reference gap is associated with a separate reference conduit, allowing the system to measure positions across a larger dynamic range by selecting the appropriate reference gap based on the workpiece position.

The invention transitions from a one-dimensional measurement (single reference gap) to a multi-dimensional approach by introducing multiple reference gaps at different distances from the measurement conduit outlet. This creates a hierarchical measurement structure where each reference gap serves a specific position range, effectively expanding the measurement capability without proportionally increasing complexity.

The measurement system is segmented into multiple independent reference channels, each with its own reference conduit and reference gap. This segmentation allows each channel to be optimized for a specific position range, improving overall adaptability while maintaining modular simplicity that limits complexity growth.

Multiple reference conduits serve universal functions by all being part of the same fluid gauge system, using the same measurement conduit and fluid source. This multi-functionality approach allows the system to handle various workpiece positions with a unified structure rather than requiring completely separate measurement systems for different ranges.

The invention introduces fluid as an intermediary medium between the measurement system and the workpiece. By using fluid pressure differences through reference gaps, the system indirectly measures position without direct contact or interaction with the workpiece surface patterns, eliminating sensitivity to wafer patterns and reducing environmental interference.

The traditional optical autofocus system is replaced with a fluid-based mechanical measurement system. This substitution eliminates the optical path that is sensitive to environmental conditions like temperature and humidity changes, and to wafer surface patterns, providing more stable and accurate measurements.