Wafer Table Positioning with Maglev Measuring Head Stability
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Solution Overview
Problem
Existing positioning devices face challenges in achieving high accuracy and reducing calibration efforts for precise positioning of a wafer table relative to a tool, due to large fluctuations and tilting in scanning distances, especially when using 6-DOF encoders.
Innovation Solution
A positioning device with two crossed linear axes, where the measuring head is supported by a second magnetic levitation unit, allowing for active movement in six degrees of freedom, and utilizing two 6-DOF encoders to measure the table's position relative to the carrier device, thereby minimizing fluctuations and tilting, and simplifying calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a measuring head is used to detect position with 6-DOF encoders, then position information can be obtained, but large fluctuations and tilting in scanning distances reduce measurement accuracy
Solution Approach 1:
The patent replaces the mechanical support system for the measuring head with a magnetic field-based support system. The measuring head is supported by a support device that generates a magnetic field, causing magnetic levitation of the measuring head. This substitution eliminates mechanical contact and associated mechanical errors (guide errors, scanning distance fluctuations, tilting), thereby stabilizing the scanning distance and improving measurement accuracy.
Solution Approach 2:
The patent changes the physical state and support parameters of the measuring head by introducing magnetic levitation. This transitions the measuring head from a mechanically constrained state to a magnetically suspended state, fundamentally altering how the measuring head is positioned and supported, thereby eliminating mechanical instability in scanning distances.
2Reliability
If mechanical support is used for the measuring head, then the structure is simple, but guide errors and fluctuations in scanning distances occur
Solution Approach 1:
The patent replaces the mechanical support system with a magnetic field-based support system. The support device generates a magnetic field that levitates the measuring head, eliminating mechanical contact. This substitution improves reliability by eliminating guide errors and scanning distance fluctuations, while the complexity is managed through the use of magnetic field generation and control systems.
3Productivity
If the measuring head remains close to the table during movement, then tracking is improved, but scanning distance fluctuations due to guide errors increase
Solution Approach 1:
The patent replaces mechanical guidance with magnetic field-based positioning. The measuring head is supported by a magnetic field generated by the support device, allowing it to track the table's movement while maintaining a stable scanning distance. This eliminates guide errors and scanning distance fluctuations that would otherwise occur with mechanical support, thereby improving both tracking efficiency and measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration significantly enhances measurement accuracy and reduces the effort required for calibration, enabling precise positioning of the wafer table relative to the tool by compensating for unwanted movements and stabilizing scanning distances.
Implementation Method 1
The table is held on one of the two linear axes by means of a first magnetic levitation unit and is actively movable in six degrees of freedom for fine positioning
Implementation Method 2
the measuring head can be actively moved in six degrees of freedom by means of a second magnetic levitation unit on the other of the two linear axes
Data Source
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AI summary
A positioning device for positioning a table (SSM) relative to a tool (T) attached to a carrier device (FAP) is disclosed. The positioning device comprises two crossed linear axes (LSX, LSY) arranged one above the other in a vertical direction (Z) for pre-positioning the table (SSM) in two linearly independent directions (X, Y), wherein the table (SSM) is held on one of the two linear axes (LSX) by means of a first magnetic levitation unit (ML1) and is actively movable in six degrees of freedom for fine positioning.The position of the table (SSM) relative to the support device (FAP) can be determined via a measuring head (FMH) arranged on the other of the two linear axes (LSY) and a first and second 6-DOF encoder (A, B), whereby the first 6-DOF encoder (A) is arranged between the support device (FAP) and the measuring head (FMH), and the second 6-DOF encoder (B) is arranged between the measuring head (FMH) and the table (SSM). For this purpose, the measuring head (FMH) can be actively moved in six degrees of freedom by means of a second magnetic levitation unit (ML2) on the other of the two linear axes (LSY).