Lithographic Stage Clamping Force Control for Inertial Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithographic apparatuses face challenges in maintaining accurate positioning and preventing substrate or patterning device slippage due to increased inertial forces during high acceleration, which can lead to overlay errors and deformation of the object table, especially when conventional vacuum clamping is insufficient.
Innovation Solution
A stage apparatus with a clamping device that applies a controlled first clamping force using electronic control, which compensates for inertial forces by actuators arranged along the circumference or perpendicular to the object's surface, ensuring stable object positioning during acceleration and deceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional vacuum clamping is used to hold the object, then the object can be held during normal operation, but the holding force becomes insufficient during high acceleration
Solution Approach 1:
The patent applies a dynamic clamping mechanism that adjusts the clamping force based on the operational state. During acceleration phases, the system activates additional clamping forces (via electrostatic actuators or spring mechanisms) to counteract inertial forces, while maintaining normal vacuum clamping during steady-state operation. This dynamic adjustment ensures sufficient holding force throughout the motion cycle without continuous application of maximum force.
Solution Approach 2:
The system anticipates inertial forces during acceleration by pre-positioning counteracting clamping mechanisms. Spring-loaded clamps or electrostatic actuators are prepared to engage immediately when acceleration occurs, providing preliminary counter-action before the object can slip. This predictive approach prevents slippage before it occurs rather than reacting after slippage begins.
2Force
If additional clamping mechanisms are introduced to increase holding force, then the holding force increases, but the device complexity increases
Solution Approach 1:
The patent combines multiple clamping approaches into a unified system where vacuum clamping, electrostatic clamping, and spring mechanisms work together as an integrated holding system. Rather than adding separate independent mechanisms, the system merges these approaches so that they cooperate seamlessly - the vacuum provides base holding, electrostatic actuators provide acceleration compensation, and springs provide mechanical backup, all controlled by a single system architecture.
Solution Approach 2:
The clamping system is designed to perform multiple functions through a single integrated mechanism. The same electrostatic actuators provide both acceleration compensation and emergency backup clamping. The spring mechanisms serve both as mechanical backups and as indicators of system state. This multi-functionality reduces the need for separate dedicated components for each function.
3Reliability
If continuous clamping force is applied to prevent slippage, then the object remains stable, but the object table deformation increases
Solution Approach 1:
The clamping force is applied periodically rather than continuously - activating during acceleration phases when inertial forces occur, and reducing or deactivating during steady-state operation. The system monitors operational state (via accelerometers or position feedback) and adjusts clamping force accordingly, providing periodic bursts of additional clamping force only when needed to counteract inertial effects, thereby minimizing overall deformation while maintaining stability during critical phases.
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 solution allows for higher acceleration of the patterning device or substrate while minimizing deformation and maintaining accurate positioning, as the controlled clamping force effectively counters inertial forces without continuous application, thus enhancing the precision and efficiency of the lithographic process.
Implementation Method 1
Some improvements have been suggested in literature to increase the holding force that holds the patterning device or substrate. Such improvements may encompass the use of additional clamping using electrostatic forces or magnetic forces
Implementation Method 2
Some improvements have been suggested in literature to increase the holding force that holds the patterning device or substrate. Such improvements may encompass the use of additional clamping using electrostatic forces or magnetic forces
Implementation Method 3
Conventionally, holding the substrate or patterning device is done by friction. A Sufficient level of friction can be applied by the use of vacuum chambers.
Data Source
AI summary
A stage apparatus for displacing an object having a substantially flat surface is described. The apparatus includes an object table for supporting the object and a positioning device for displacing the object table in a first direction. The apparatus further includes a clamping device for clamping the object to the object table by a first clamping force, the first clamping force being controlled by an electronic control unit based upon a state of the object.