Lithographic Stage Actuator Arrangement for Slip Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional lithographic apparatus stage systems experience slip between the substrate table and the encoder block due to hot spot peaks of material stress, limiting acceleration levels and leading to misalignment and overlay errors.
Innovation Solution
The stage system incorporates reluctance actuators spaced perpendicular to the driving direction, distributing forces tangentially to reduce stress concentrations and maintain even normal forces, thereby minimizing the risk of slip during high accelerations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If Lorentz actuators are arranged serially in the driving direction, then the stage system can achieve the required driving force, but hot spot peaks of material stress occur in the burls resulting in increased local shear forces and reduced normal forces which may cause slip between the substrate table and encoder block
Solution Approach 1:
The actuator is moved from a serial arrangement in the driving direction to a lateral arrangement perpendicular to the driving direction. This dimensional change redistributes the force application points, eliminating hot spot peaks of material stress in the burls and preventing local slip while maintaining the required driving force through the lateral actuator configuration
2Productivity
If acceleration levels are increased to increase throughput, then productivity improves, but the risk of slip between the substrate table and encoder block increases due to hot spot peaks of material stress
Solution Approach 1:
By arranging the actuator laterally perpendicular to the driving direction, the force distribution across the burls is fundamentally changed. This allows higher acceleration levels to be applied without creating the hot spot stress concentrations that would cause slip, thereby enabling increased throughput while maintaining reliability
3Measurement precision
If the clamping force is increased to prevent slip, then positioning accuracy improves, but the device complexity and potential for substrate damage increase
Solution Approach 1:
The lateral arrangement of the actuator fundamentally changes the force distribution mechanism, eliminating the need for increased clamping force to prevent slip. The even distribution of normal forces across all burls provides inherent slip prevention at normal clamping levels, simplifying the overall system while maintaining positioning accuracy
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 arrangement allows for increased acceleration levels without slip, ensuring precise positioning and reducing the risk of misalignment, thus enhancing the throughput and accuracy of the lithographic apparatus.
Implementation Method 1
the object table support comprises at least one first actuator to drive the object table support in a first driving direction substantially parallel to the object table support surface
Implementation Method 2
The substrate table is clamped by means of a vacuum clamp and/or electrostatic clamp on the substrate table support surface
Implementation Method 3
The substrate table is clamped by means of a vacuum clamp and/or electrostatic clamp on the substrate table support surface
Implementation Method 4
The normal force, i.e., the force with which the substrate table is pressed against the encoder block multiplied by the friction coefficient should be larger than the shear force in the burls
Data Source
AI summary
A movable stage system is configured to support an object. The stage system comprises an object table configured to support the object and an object table support defining an object table support surface configured to support the object table. The object table support comprises at least one first actuator to drive the object table support in a first driving direction substantially parallel to the object table support surface. In a projection on a plane parallel to the object table support surface the at least one actuator is spaced with respect to the object table in a direction perpendicular to the first driving direction such that the risk on slip between the object table support and the object table supported thereon is decreased.