Floating Wafer Stage Cooling and Inclination Control in Vacuum
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Solution Overview
Problem
Existing stage apparatuses in high vacuum environments, particularly those using floating stages, face challenges in maintaining sufficient positional accuracy due to various error factors, including thermal expansion and mechanical stabilization issues, which hinder precise wafer positioning during semiconductor manufacturing and inspection processes.
Innovation Solution
A stage apparatus with a first stage moving in a first direction, a second stage floating orthogonally, a refrigerant-based cooling unit, and a control device to manage the inclination of the second stage relative to the first, ensuring accurate positional alignment through cooling and angular control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a floating stage is used to enable non-contact movement, then mechanical stabilization is eliminated and high positional accuracy can be achieved, but thermal expansion and angular deviations occur due to heat generation in vacuum environment
Solution Approach 1:
The stage is divided into multiple independent floating sections (first stage, second stage, third stage) that can be cooled independently. Each stage has its own cooling paths, allowing localized thermal management without affecting the entire stage structure, thereby maintaining positional accuracy while handling heat generation.
Solution Approach 2:
A refrigerant is introduced as an intermediary cooling medium that circulates through heat exchange paths in contact with each stage. The refrigerant absorbs heat generated by motors and electronics in the vacuum environment, preventing thermal expansion and maintaining thermal stability of the floating stage structure.
2Ease of operation
If motors are installed in the floating stage to enable movement, then propulsion and positioning functions are achieved, but heat generation occurs that cannot be dissipated by solid heat conduction in vacuum
Solution Approach 1:
A refrigerant circulation system is implemented where the refrigerant flows through heat exchange paths within and around the motors. This fluid-based cooling system efficiently removes heat generated by motor operation in the vacuum environment where conventional air cooling or solid conduction is ineffective.
Solution Approach 2:
The cooling system is designed to dynamically adapt to the thermal load of the motors. The refrigerant flow rate and temperature can be adjusted based on the operational state of the motors, ensuring optimal heat dissipation during movement operations while maintaining positional accuracy.
3Measurement precision
If laser interferometer measurement is used to achieve picometer-level distance measurement, then theoretical positional accuracy is sufficient, but various error factors in floating stage combine to deteriorate actual positional accuracy
Solution Approach 1:
The laser interferometer provides real-time feedback on the positional state of the floating stage. This measurement feedback is combined with temperature monitoring from the refrigerant system to create a closed-loop control system that compensates for thermal expansion and angular deviations, maintaining actual positional accuracy at the theoretical picometer level.
Solution Approach 2:
The system actively monitors and adjusts operational parameters including refrigerant temperature, flow rate, and motor current to minimize thermal effects. By controlling these parameters, the system reduces thermal expansion and angular deviations, ensuring that the actual positional accuracy matches the theoretical measurement capability of the laser interferometer.
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
The solution enhances positional accuracy of the floating stage by reducing thermal expansion and angular deviations, allowing for precise wafer positioning and improved manufacturing and inspection processes.
Implementation Method 1
a first cooling unit configured to cool the table of the first stage with a refrigerant
Implementation Method 2
a magnetic floating type that controls a floating amount using electromagnetic force
Data Source
AI summary
A stage apparatus includes a lower stage that moves in a Y-axis direction, an upper stage that floats from the lower stage and moves at least in an X-axis direction orthogonal to the Y-axis direction, a heat exchanger that cools a Y table of the lower stage with a refrigerant, and a control device that controls an inclination of the lower stage with reference to the Y table cooled by the heat exchanger.