Lithography Alignment Weighting by Transmission Data
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Solution Overview
Problem
Current metrology systems in lithographic apparatuses face challenges in accurately determining the position of target structures on substrates due to variations in alignment radiation transmission and stage/sensor position data, which affect the precision of alignment and overlay measurements.
Innovation Solution
A method involving the use of transmission data to determine the weighting of position data based on alignment radiation transmission, and tuning the spectral characteristics of the alignment radiation to improve alignment accuracy, is implemented. This includes obtaining transmission data and position data, determining a weighting factor, and adjusting the spectral characteristics to match the position data, thereby enhancing the precision of position determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transmission data and position data are used directly without weighting, then the alignment process is simple, but the position determination accuracy deteriorates due to variations in radiation transmission
Solution Approach 1:
The patent applies parameter changes by introducing a weighting factor that modifies the position data based on transmission data. The weighting factor is determined by comparing the actual transmission of alignment radiation with expected transmission values, and this weight is applied to correct the position data accordingly. This resolves the contradiction by improving position determination accuracy through parameter adjustment without fundamentally changing the alignment process architecture.
2Measurement precision
If spectral characteristics of alignment radiation are not tuned, then the system operation is simple, but the alignment accuracy deteriorates due to mismatches between radiation properties and sensor response
Solution Approach 1:
The patent applies parameter changes by tuning the spectral characteristics of the alignment radiation to match the sensitivity profile of the position sensor. This involves adjusting the wavelength distribution or spectral content of the radiation source to optimize the signal-to-noise ratio and measurement accuracy. The spectral tuning improves alignment accuracy by ensuring optimal interaction between radiation and sensor without requiring fundamental system redesign.
3Measurement precision
If weighting based on transmission data is applied, then position determination accuracy improves, but the computational complexity and processing time increase
Solution Approach 1:
The patent applies preliminary action by pre-calculating or pre-determining the weighting factors based on transmission data that can be obtained in advance or during routine operations. The transmission characteristics are measured and stored, and the weighting factors are prepared beforehand, so that during actual alignment operations, the correction can be applied quickly without extensive real-time computation. This reduces processing time while maintaining accuracy improvements.
Data Source
AI summary
Disclosed is a method for determining a stage position or correction therefor in a lithographic process. The method comprises obtaining transmission data describing the transmission of alignment radiation onto the substrate; obtaining position data relating to a stage position of said stage and/or a sensor position of said sensor. A weighting is determined for the position data based on said transmission data. The position based on said transmission data, position data and weighting.