Polynomial Overlay Correction for EUV Lithography
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Solution Overview
Problem
The increasing integration density of semiconductor devices requires more precise overlay correction in EUV lithography systems, as existing methods struggle to accurately accommodate variations in overlay quantities across different measurement positions, affecting the fabrication of semiconductor devices.
Innovation Solution
An overlay correction method involving the measurement and fitting of overlay components with polynomial functions to construct a correction model, which includes components parallel and intersecting directions, and manufacturing a reticle based on this model to correct higher-order terms and improve alignment precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional overlay measurement and correction methods are used, then basic alignment between lower and upper patterns can be achieved, but higher-order distortion terms cannot be accurately corrected, leading to insufficient manufacturing precision for high integration density devices
Solution Approach 1:
The patent changes the mathematical parameters of the correction model by introducing polynomial functions of higher degrees (beyond conventional linear or quadratic models). This allows the system to capture and correct higher-order distortion terms that arise in EUV lithography, thereby improving overlay correction precision without requiring a complete redesign of the measurement system
Solution Approach 2:
The patent replaces conventional mechanical or simple optical alignment methods with a sophisticated computational approach using polynomial fitting and mathematical modeling. This substitution enables accurate correction of complex distortion patterns through data processing rather than mechanical adjustment, achieving higher precision while managing system complexity through software-based solutions
2Measurement precision
If overlay measurement is performed at multiple positions on the substrate, then distortion variations can be detected, but the complexity of obtaining and processing overlay quantities increases
Solution Approach 1:
The patent divides the substrate into multiple measurement positions and segments the overlay measurement process into discrete sampling points. By measuring overlay quantities at multiple segmented locations and then fitting polynomial functions to these segmented data points, the system achieves comprehensive distortion characterization while organizing the complex measurement data into manageable segments that can be processed systematically
Solution Approach 2:
The patent introduces polynomial fitting functions as an intermediary between raw overlay measurement data and the final correction model. This intermediary mathematical layer processes the multiple overlay quantities obtained from different positions, transforming them into a unified correction framework that captures distortion variations without requiring direct manual processing of each individual measurement point
Data Source
AI summary
Disclosed are an overlay correction method, a method of evaluating an overlay correction operation, and a method of fabricating a semiconductor device using the overlay correction method. The overlay correction method may include measuring an overlay between center lines of lower and upper patterns on a wafer, fitting each of components of the overlay with a polynomial function to obtain first fitting quantities, and summing the first fitting quantities to construct a correction model. The components of the overlay may include overlay components, which are respectively measured in two different directions parallel to a top surface of a reticle. The highest order of the polynomial function may be determined as an order, which minimizes a difference between the polynomial function and each of the components of the overlay or corresponds to an inflection point in a graph of the difference with respect to the highest order of the polynomial function.