Segmented Encoder Scales for Semiconductor Wafer Positioning
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Solution Overview
Problem
The high cost and complexity of producing and assembling long, high-accuracy scales for precise positioning systems in semiconductor wafer production lead to increased expenses and difficulties in manufacturing machines for producing circuitry on wafers.
Innovation Solution
A positioning system utilizing multiple short encoder scales and read heads, where each read head can read one scale, allowing for handover of reading results between heads to maintain accuracy without the need for a long encoder scale, reducing costs and simplifying assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long encoder scale is used to cover the entire movement range of the stage, then positioning precision is maintained, but the cost and difficulty of production and assembly increase significantly
Solution Approach 1:
The patent divides the long encoder scale into multiple short scale segments (first scale, second scale, third scale, etc.) that are mounted at different positions along the movement path. Each read head reads one short scale segment at a time, and the control unit combines readings from multiple segments to determine the overall position. This segmentation reduces the complexity of producing and assembling each individual scale while maintaining the total measurement range needed for full stage movement.
2Measurement precision
If a long encoder scale is used to cover the entire movement range, then positioning accuracy is maintained, but the cost of the positioning system increases essentially
Solution Approach 1:
The patent segments the long scale into multiple short scales that can be manufactured independently using standard production processes. Each short scale is cheaper to produce than a single long scale, and the modular nature allows for easier inventory management and replacement. The control unit synthesizes position information from multiple read heads reading different short scales to achieve the same overall positioning accuracy.
3Ease of manufacture
If multiple short scales are used instead of one long scale, then cost and assembly simplicity are improved, but the system requires multiple read heads and coordination logic
Solution Approach 1:
The patent merges the position information from multiple read heads reading different short scales into a unified position measurement through the control unit. The control unit receives signals from all read heads, correlates them with their respective scale positions, and combines them to determine the absolute position of the stage. This merging approach allows the system to use multiple simple short scales while achieving the functionality of a single long scale.
Data Source
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AI summary
A positioning device (30) and a positioning method for positioning supporting means (10) for supporting an article (2), in particular a stage 10 for supporting a semiconductor wafer 2, are provided. The positioning device (30) comprises at least two scales (33, 34, 35) for measuring the position of said supporting means (10), and at least two read heads (31, 32) for reading said at least two scales (33, 34, 35), wherein each one of said at least two read heads (31, 32) is positioned such that at least one (31) of said at least two read heads (31, 32) can read one scale (33) of said at least two scales (33, 34, 35).