Reticle Alignment Using Layer Weighting Factors
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Solution Overview
Problem
The challenge in photolithographic processes for forming multiple layers on a semiconductor wafer is the difficulty in achieving precise alignment between layers, leading to overlay errors that can compromise the quality of electronic devices as the process becomes finer and more complex.
Innovation Solution
A method that utilizes alignment parameters from previous layers to calculate and set the alignment for subsequent layers, using a weighting factor approach to improve the alignment setting of reticles during the exposure process, thereby enhancing the patterning process for multiple layers on a wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional alignment methods using single layer alignment marks are used, then the alignment process is simple, but the alignment precision between layers deteriorates due to cumulative errors
Solution Approach 1:
The alignment process is segmented into multiple independent measurement stages. Instead of relying on a single alignment mark, the patent divides the alignment task into measuring alignment parameters from multiple previous layers separately, then combining these measurements through a calculation unit to determine the final reticle alignment setting. This segmentation reduces cumulative error propagation while maintaining process manageability.
Solution Approach 2:
A calculation unit acts as an intermediary between the measurement of alignment parameters from multiple layers and the final reticle positioning. This intermediary component processes the alignment parameters from first and second layers, applies weighting factors, and calculates the optimal alignment setting for the third reticle, thereby improving precision without requiring direct complex multi-layer coordination.
2Manufacturing precision
If alignment parameters from multiple previous layers are measured and combined, then the alignment precision improves, but the measurement and calculation complexity increases
Solution Approach 1:
The calculation unit serves as an intermediary that automatically processes the complex task of combining alignment parameters from multiple layers. It receives alignment parameters from the first and second layers, applies predetermined weighting factors based on layer properties, and computes the final alignment setting. This intermediary automates the complex measurement combination process, reducing the practical difficulty despite the increased measurement requirements.
Solution Approach 2:
The patent transforms the alignment control problem from direct geometric alignment to a parameter-based calculation problem. By measuring alignment parameters (such as offset, rotation, scaling) from multiple layers and combining them through weighted calculations, the system converts complex multi-dimensional alignment challenges into manageable parameter adjustments that can be systematically processed and optimized.
3Measurement precision
If weighting factors are applied to combine alignment parameters from multiple layers, then the alignment setting accuracy improves, but the calculation complexity increases
Solution Approach 1:
The patent introduces weighting factors as additional parameters to optimize the alignment calculation. By assigning different weights to alignment parameters from different layers based on their relative importance and measurement accuracy, the system achieves more accurate alignment settings. The calculation unit processes these weighted parameters systematically, transforming a simple averaging problem into an optimized parameter combination that improves precision without excessive complexity.
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 method improves the alignment precision between layers, reducing overlay errors and ensuring the quality of electronic devices by using the measured alignment parameters and weighting factors to accurately position reticles for exposure, thus enhancing the overall patterning process for multiple layers on a wafer.
Implementation Method 1
an exposure apparatus for transferring a pattern of a reticle onto a wafer... The projection module is configured to project the pattern of the reticle onto the wafer
Data Source
AI summary
An exposure apparatus for transferring a pattern of a reticle onto a wafer is provided. The exposure apparatus includes an illumination module, a reticle stage, a projection module, a wafer stage, and a control unit. The control unit is configured to calculate an alignment setting of the reticle. The wafer includes a first layer and a second layer disposed on the first layer. The first layer includes a first alignment parameter. The second layer includes a second alignment parameter. The control unit obtains a first weighting factor predetermined according to a property of the first layer, and a second weighting factor predetermined according to a property of the second layer. The alignment setting of the reticle is calculated according to the first alignment parameter, the first weighting factor, the second alignment parameter, and the second weighting factor.