Adaptive Feedforward Control for Lithographic Apparatus Disturbance Compensation
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Solution Overview
Problem
Current control systems in lithographic apparatuses, such as iterative learning control, are inadequate for handling disturbances that change due to variations in physical quantities, leading to increased complexity and suboptimal disturbance cancellation, especially in multi-dimensional control scenarios where cross-talk between dimensions occurs.
Innovation Solution
A control system where a gain factor parameter is dependent on the value of a further physical quantity, allowing for adaptive feedforward compensation to counteract disturbances and improve accuracy by incorporating cross-talk variations into the feedforward signal, thereby enhancing the control system's ability to handle changing conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If iterative learning control with multiple time series tables is used to handle disturbances varying with physical quantities, then disturbance cancellation accuracy is improved, but device complexity and setup time increase
Solution Approach 1:
The patent applies parameter changes by making the gain factor parameter dynamic rather than static. Instead of using multiple fixed time series tables for different disturbance conditions, the system uses a single time series table where the gain factor is continuously adjusted based on real-time physical quantity measurements. This allows the control system to adapt to varying disturbances through parameter modulation rather than switching between multiple pre-configured tables, thereby reducing complexity while maintaining accuracy.
2Manufacturing precision
If multiple time series tables are used to compensate for different disturbance conditions, then disturbance cancellation is improved, but set-up time and calibration time increase
Solution Approach 1:
The patent implements dynamics by transitioning from static multiple time series tables to a dynamic single time series table with adaptive gain factor. The gain factor is continuously adjusted during operation based on measured physical quantities, allowing the system to adapt to changing conditions in real-time without requiring manual reconfiguration or recalibration for different disturbance scenarios. This dynamic approach eliminates the need for extensive setup time associated with configuring multiple tables while maintaining effective disturbance compensation.
3Manufacturing precision
If iterative learning control is used for multi-dimensional control, then control accuracy is improved, but cross-talk between dimensions cannot be adequately compensated
Solution Approach 1:
The patent applies universality by designing a single time series table that serves multiple functions: it handles not only the primary control dimension but also compensates for cross-talk effects in other dimensions through the adaptive gain factor. The gain factor adjustment mechanism is universal enough to address disturbances in any dimension, making the control system versatile for multi-dimensional control scenarios without requiring separate specialized tables for each dimension or cross-talk compensation.
Data Source
AI summary
A lithographic apparatus includes a first control system to control a first physical quantity in the lithographic apparatus. A parameter in the first control system is dependent on a value of a further physical quantity in the lithographic apparatus. The parameter may be included in a feedforward path. An input of the feedforward path may be connected to a second control system, the second control system to control a second physical quantity in the lithographic apparatus. The feedforward path may provide a feedforward signal to the first control system in dependency on a signal in the second control system. The further physical quantity may include the second physical quantity.