Lithographic Illuminator Slit Uniformity Correction
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Solution Overview
Problem
Lithographic apparatuses face challenges in maintaining illumination uniformity, particularly in small-field exposures, where existing correction methods like Uniform Refresh (UR) do not provide optimal compensation, leading to slit uniformity drift and transmission losses.
Innovation Solution
A system with a controller and motion control system adjusts the position of finger assemblies within the illumination slit uniformity correction system, modifying calibration data and compensating for changes in finger assembly shape due to radiation exposure to achieve optimal slit uniformity across varying exposure fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If existing uniformity correction methods (Uniform Refresh) are used, then illumination uniformity can be corrected, but slit uniformity drift occurs and transmission losses increase in small-field exposures
Solution Approach 1:
The patent implements dynamic adaptation of the uniformity correction system to varying exposure fields. The controller dynamically determines the optimal position of finger assemblies based on the specific exposure field size and shape, allowing the system to adapt from static calibration to dynamic optimization. This resolves the contradiction by enabling the system to maintain uniformity across different field sizes without drift or transmission losses.
Solution Approach 2:
The patent changes the operational parameters of the uniformity correction system by modifying the position and configuration of finger assemblies according to the exposure field characteristics. Instead of using fixed calibration data, the system adjusts parameters (finger position, exposure field definition) to optimize performance for each specific exposure scenario, thereby eliminating uniformity drift and transmission losses.
2Manufacturing precision
If finger assemblies are positioned to correct uniformity in full field, then uniformity is optimized for maximum exposure, but transmission efficiency decreases for partial exposure fields
Solution Approach 1:
The patent applies local quality optimization by tailoring the uniformity correction specifically to the actual exposure field being used. Instead of a one-size-fits-all approach, the system determines the optimal finger assembly position based on the specific exposure field (full field, half field, quarter field, etc.), thereby optimizing transmission efficiency for each local exposure scenario rather than compromising for maximum field coverage.
Solution Approach 2:
The patent employs partial action by adjusting the uniformity correction system to match the actual exposure field size. For partial exposure fields (half field, quarter field), the system positions finger assemblies to optimize only the relevant portion of the illumination slit, avoiding excessive correction actions that would reduce transmission efficiency for the actual used field area.
3Productivity
If calibration data is used for maximum exposure field, then uniformity is optimized for full field, but CD drift increases for smaller exposure fields
Solution Approach 1:
The patent implements dynamic adaptation where the controller determines the optimal finger assembly position based on the specific exposure field size. This dynamic approach allows the system to maintain critical dimension stability across different field sizes by adjusting the uniformity correction parameters in real-time, rather than relying on static calibration data that causes CD drift for smaller fields.
Solution Approach 2:
The system uses feedback from the exposure field characteristics to determine the optimal finger assembly position. By monitoring the actual exposure field size and shape, the controller adjusts the uniformity correction parameters accordingly, providing feedback-based control that prevents CD drift for partial exposure fields while maintaining productivity for full field operations.
Data Source
AI summary
Systems, apparatuses, and methods are provided for adjusting illumination slit uniformity in a lithographic apparatus. An example method can include determining whether an exposure field for a wafer exposure operation is less than a maximum exposure field of a uniformity correction system. In response to determining that the exposure field is less than the maximum exposure field, the example method can include modifying illumination slit uniformity calibration data associated with the maximum exposure field to generate modified illumination slit uniformity calibration data associated with the exposure field. Subsequently, the example method can include determining an optimal position of a finger assembly of the uniformity correction system based on the modified illumination slit uniformity calibration data.