Lithographic Apparatus Lens Heating Control
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Solution Overview
Problem
Existing techniques to address lens heating in lithographic apparatuses do not completely eliminate aberrations and errors, leading to residual issues that can affect image quality during the manufacturing of devices like integrated circuits.
Innovation Solution
A control system is implemented to automatically reduce the throughput of the lithographic apparatus when aberrations and errors due to heating exceed a certain threshold, using a combination of energy sensors, a lens-heating model, and controller to apply corrections through adjustable optical elements and altering the exposure profile, including reducing the duty cycle and beam strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cooling lenses or heating lenses with additional heaters is used to reduce lens heating effects, then thermal gradients are reduced, but residual aberrations still exist and the system complexity increases
Solution Approach 1:
The patent changes operational parameters (beam strength, duty cycle, exposure timing) rather than modifying the physical structure of the projection system. By dynamically adjusting these parameters based on real-time temperature monitoring and predictive modeling, the system reduces lens heating effects without adding complex hardware components like cooling systems or additional heaters.
Solution Approach 2:
The patent implements a feedback control system that continuously monitors lens temperature and adjusts operational parameters accordingly. The control system uses real-time temperature data and predictive models to automatically modify beam strength and duty cycle, creating a closed-loop control mechanism that maintains image quality while avoiding the need for complex physical modifications to the projection system.
2Manufacturing precision
If adjustable elements are introduced into the projection system to compensate for lens heating effects, then aberrations are reduced, but the device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical/optical compensation mechanisms (adjustable elements) with a computational approach. Instead of physically adjusting optical components to correct aberrations, the system uses software-based predictive modeling and operational parameter optimization to prevent aberrations from occurring in the first place, thereby eliminating the need for complex adjustable elements.
Solution Approach 2:
The patent performs preliminary actions by predicting lens heating effects before they occur and adjusting operational parameters in advance. The control system uses predictive models to anticipate temperature changes and pre-adjusts beam strength and duty cycle, preventing aberrations before they manifest, rather than requiring corrective adjustable elements during operation.
3Manufacturing precision
If the duty cycle and beam strength are reduced to allow cooling time, then lens heating errors decrease, but the throughput of the apparatus decreases
Solution Approach 1:
The patent makes the operational parameters dynamic rather than static. The beam strength and duty cycle are continuously adjusted based on real-time temperature monitoring and predictive modeling, allowing the system to optimize between throughput and image quality on a per-exposure basis. This dynamic approach enables higher overall throughput compared to uniformly reduced parameters.
Solution Approach 2:
The patent changes operational parameters (beam strength, duty cycle, exposure timing) based on predictive modeling and real-time temperature data. By strategically adjusting these parameters only when necessary to prevent aberrations, the system maintains high throughput during normal operation while preventing lens heating errors, rather than permanently reducing throughput.
4Productivity
If continuous operation is maintained to maximize throughput, then productivity increases, but lens heating causes aberrations and errors in the projected image
Solution Approach 1:
The patent implements real-time feedback control that continuously monitors lens temperature and adjusts operational parameters during operation. This allows the system to maintain high throughput through continuous operation while using feedback-based parameter adjustments to prevent aberrations, resolving the contradiction between productivity and image quality.
Solution Approach 2:
The patent performs preliminary adjustments to operational parameters based on predictive modeling before lens heating causes aberrations. By anticipating temperature changes and pre-adjusting beam strength and duty cycle, the system can maintain continuous operation for high throughput while preventing image quality degradation through proactive parameter optimization.
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 approach effectively keeps lens heating errors within acceptable limits by reducing throughput and allowing for additional cooling time, thereby improving image quality and reducing the need for costly corrective measures.
Implementation Method 1
the elements of the projection system inevitably absorb a certain amount of energy from the beam and therefore heat up
Implementation Method 2
As the elements of the projection system heat up, their shape and/or position may change
Data Source
AI summary
In a lithographic apparatus, a control system is provided to automatically reduce throughput in the event that lens-heating aberrations exceed a certain threshold. The determination of whether lens-heating aberrations will exceed the threshold may be based upon a prediction, e.g. using a lens-heating model, or on measurements taken from a previously exposed substrate. Reduction of throughput of the device manufacture may be effected by reducing beam power or the duty cycle of the apparatus. In a particular embodiment, the time taken for substrate movement between exposure portions is increased.