Microlithography Stage Control Using Iterative Feedback Tuning
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Solution Overview
Problem
Microlithography systems face challenges in achieving precise positioning and motion control due to following-errors and vibration disturbances, which compromise the accuracy of micro-device manufacturing.
Innovation Solution
The implementation of an iterative feedback tuning (IFT) method using multiple controllers to minimize cost-functions and synchronize stage movements, combining feedback and feed-forward control to improve convergence and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional feedback control is used to reduce following-errors, then stage positioning accuracy is improved, but control response speed and precision are insufficient to meet nanometer-range requirements
Solution Approach 1:
The patent implements iterative feedback tuning where the controller continuously receives position feedback from measurement systems, compares actual stage positions with intended trajectories, and adjusts control parameters to minimize following-errors. This closed-loop feedback mechanism enables the system to adaptively improve positioning accuracy while maintaining nanometer-range precision requirements.
Solution Approach 2:
The control system performs self-tuning through iterative feedback adjustment, automatically optimizing control parameters without external intervention. The system uses its own measurement data and following-error information to refine controller performance, enabling continuous improvement of positioning accuracy and response precision.
2Stability of the object's composition
If stage mass is increased to improve rigidity and reduce vibration, then positioning stability is improved, but acceleration and deceleration performance deteriorate
Solution Approach 1:
The control system applies preliminary feed-forward control actions based on predicted stage motion requirements. By anticipating acceleration and deceleration needs before they occur, the controller can optimize force application timing and magnitude, enabling rapid speed changes without compromising positioning stability during exposure.
Solution Approach 2:
The patent implements dynamic control parameter adjustment that adapts to changing motion conditions. The controller modifies feedback gains and control forces in real-time based on stage velocity, acceleration, and position, enabling the system to achieve both rapid acceleration performance and stable positioning throughout the motion cycle.
3Manufacturing precision
If feedback control gains are increased to reduce following-errors, then trajectory tracking accuracy is improved, but system stability and susceptibility to vibration deteriorate
Solution Approach 1:
The control system dynamically adjusts feedback gains based on operating conditions, stage velocity, and measured vibration levels. This adaptive gain scheduling enables high tracking accuracy during steady-state exposure while maintaining system stability during acceleration, deceleration, and vibration-prone conditions through real-time parameter optimization.
Solution Approach 2:
The patent implements iterative tuning of control parameters including feedback gains, filter coefficients, and control forces. The system systematically adjusts these parameters to optimize the balance between trajectory tracking accuracy and system stability, using measurement data to refine parameter values and eliminate resonance and vibration.
Data Source
AI summary
Stage assemblies and control methods are disclosed. An exemplary assembly includes a first stage and first and second controllers. The first controller feedback-controls the first stage according to a respective parameter vector. The second controller controls the first stage by feed-forward control, according to a respective parameter vector. The controllers perform iterative feedback tuning IFT, including minimization of a cost-function of the parameter vectors from the first and second controllers. The second controller receives data including first-stage trajectory, and the first controller receives data including first-stage following-error. A suitable application of the assembly is in a microlithography system or other high-precision system.