Lithographic Apparatus Lot Sequencing for Thermal Distortion Control
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Solution Overview
Problem
In high-volume lithographic manufacturing, thermal distortions across different lots processed in the same apparatus are unpredictable, leading to performance errors due to lingering thermal effects from previous lots, which existing techniques cannot accurately correct, especially when handling diverse product and layer types.
Innovation Solution
A method is developed to determine an optimal lot processing sequence for a lithographic apparatus using a thermal model to simulate thermal behavior across different sequences, allowing for the determination of a preferred thermal behavior by comparing simulated thermal behaviors, and implementing lot sequencing rules to control the processing sequence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If lots are processed in a fixed sequence, then manufacturing throughput is maintained, but thermal distortions cause performance errors due to unpredictable thermal effects from previous lots
Solution Approach 1:
The patent implements dynamic lot sequencing by using a thermal model to predict thermal behavior and adjusting the processing sequence in real-time. Instead of a fixed sequence, the system evaluates thermal characteristics of pending lots and reorders them dynamically to minimize cumulative thermal effects, thereby maintaining both high throughput and pattern application accuracy.
Solution Approach 2:
The system changes the parameter of lot sequence based on thermal model predictions. By analyzing thermal characteristics (such as heating rates, cooling rates, and thermal mass) of different lots and adjusting the processing order according to these parameters, the system optimizes thermal behavior to reduce distortions while maintaining manufacturing productivity.
2Manufacturing precision
If thermal modeling is used to compensate for distortions, then some thermal effects are corrected, but unpredictable thermal behavior from diverse lot types remains uncorrected
Solution Approach 1:
The patent applies preliminary thermal modeling to predict the thermal behavior of each lot before processing. By calculating thermal characteristics in advance and using these predictions to determine the optimal processing sequence, the system proactively prevents unpredictable thermal effects rather than attempting to correct them after they occur, enabling effective handling of diverse lot types.
Solution Approach 2:
The system incorporates feedback from actual thermal measurements and model predictions to continuously refine lot sequencing decisions. Thermal behavior data from processed lots feeds back into the thermal model, improving predictions for subsequent lots and enabling the system to adapt to diverse lot types while maintaining manufacturing precision.
3Manufacturing precision
If lots are resequenced to optimize thermal behavior, then thermal-induced errors are reduced, but processing time increases due to sequence optimization calculations
Solution Approach 1:
The patent implements partial optimization by focusing thermal sequencing efforts on critical lots or time windows where thermal effects are most significant. Rather than optimizing the entire production schedule, the system applies sequencing optimization to specific subsets of lots, reducing computational overhead while still achieving substantial thermal error reduction.
Solution Approach 2:
The system performs preliminary thermal analysis and sequence determination in advance, using cached thermal model data and pre-calculated sequences for common lot types. This reduces real-time computational requirements and minimizes the time lost to optimization calculations during actual production.
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 improves the accuracy and consistency of pattern application across lots, reducing thermal-induced errors and enhancing overall performance by optimizing the sequencing of lots to minimize thermal variations and accumulation of thermal effects.
Implementation Method 1
thermal behavior of one or more components within the lithographic apparatus
Implementation Method 2
heating effects build and dissipate within components of the apparatus
Data Source
AI summary
A lithographic apparatus applies patterns to substrates, the substrates being processed as a plurality of lots. Each lot of substrates receives a particular layer pattern under layer-specific operating conditions. A thermal model is provided for modeling and compensating one or more characteristics of thermal behavior of components within the lithographic apparatus, in response to the varying layer-specific operating conditions associated with a sequence of lots. The thermal model is also used to simulate thermal behavior of the apparatus when processing a given collection of lots in different possible sequences. Based on comparison of the simulated thermal behavior in different sequences of lots, an optimized sequence is determined. Optionally, lot sequencing rules are determined and used to obtain a preferred thermal behavior when processing a collection of lots in the future.