Magnetostrictive Actuator for Patterning Device Anti-Slip
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Solution Overview
Problem
Lithographic patterning devices experience slippage during high acceleration and deceleration in lithographic processes, leading to misalignment issues due to insufficient frictional forces, which existing solutions like vacuum clamps and friction coatings cannot adequately address at increasing production rates.
Innovation Solution
A patterning device transport system incorporating a support device, a holding device, and a magnetostrictive actuator that applies a force to the patterning device concurrently with its movement, effectively eliminating slippage by supplementing the frictional force with a direct force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vacuum clamps are used to hold the patterning device, then the patterning device can be held in place during scanning, but the friction force is limited by the maximum differential pressure between atmosphere and vacuum, which is only about 1 bar, and the small surface area limits the normal force that can be generated
Solution Approach 1:
A magnetic field is introduced as an intermediary force between the patterning device and the support structure. Magnets embedded in the support structure interact with a magnetically responsive coating on the patterning device, creating a magnetic attraction force that supplements or replaces the vacuum clamp friction force, enabling reliable holding during high-acceleration scanning operations
Solution Approach 2:
The holding mechanism transitions from relying solely on vacuum pressure (limited to 1 bar differential) to utilizing magnetic field strength, which can be adjusted and scaled independently of atmospheric pressure constraints, thereby increasing the available holding force
2Reliability
If friction coatings are used to increase friction between the patterning device and clamp, then the patterning device can be held in place, but the friction coefficient is limited to approximately 0.25, which is insufficient for high acceleration rates
Solution Approach 1:
The support structure employs a composite approach combining vacuum clamp surfaces with embedded magnets and magnetically responsive coatings on the patterning device. This composite system leverages both vacuum adhesion and magnetic attraction to generate sufficient total holding force for high-acceleration operations
3Productivity
If the patterning device is scanned at constant velocity to increase production rate, then productivity improves, but during acceleration and deceleration portions, large inertial forces cause the patterning device to slip
Solution Approach 1:
The magnetic field and vacuum clamp system are configured to provide preliminary anti-action by generating holding forces that counteract the inertial forces during acceleration and deceleration phases, preventing slippage before it occurs and maintaining alignment precision throughout the scanning cycle
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 ensures minimal patterning device slip during high-speed and high-acceleration movements, maintaining precise alignment and improving production efficiency by providing a reliable anti-slip mechanism without additional mass or complex controls.
Implementation Method 1
a magnetostrictive actuator configured to apply a force to the patterning device
Data Source
AI summary
In a lithographic apparatus, slippage of a patterning device is substantially eliminated during movement of a patterning device stage by providing a magnetostrictive actuator to apply an accelerating force to the patterning device to compensate for forces that would otherwise tend to cause slippage when the patterning device stage moves.