Photolithography Alignment Using APD-Based Wafer Grid Fitting
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Solution Overview
Problem
Existing lithographic processes face challenges in obtaining accurate alignment data without increasing the number of alignment marks or measurement time, which affects wafer throughput and overlay precision.
Innovation Solution
A metrology device and method that collects radiation interacting with alignment marks to determine alignment position deviations (APDs) and deformation gradients, allowing for improved wafer grid fitting and alignment correction using optical systems and processing systems to derive rotation measurements (Rz) without additional marks or time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If more alignment marks are used to improve alignment accuracy, then measurement precision is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent changes the measurement parameters by calculating second derivatives (curvature) of alignment mark positions rather than simply measuring positions. This mathematical transformation extracts more information from the same physical marks, improving alignment accuracy without adding more marks. The system computes curvature values Kx and Ky from position data, enabling detection of subtle wafer deformations that traditional linear measurements would miss.
Solution Approach 2:
The patent transitions from measuring only positional deviations to measuring curvature (second spatial derivative) of the alignment marks. This adds a dimensional aspect to the measurement - instead of just where the mark is, the system measures how the mark's position changes across space, providing information about wafer warpage and deformation that cannot be obtained from single-point measurements alone.
2Manufacturing precision
If more alignment marks are added to improve overlay precision, then manufacturing precision is improved, but the number of components increases
Solution Approach 1:
The system transforms the measurement approach by computing curvature (second derivatives) of alignment mark positions. This parameter transformation allows the extraction of wafer deformation information from existing marks, achieving improved overlay precision without increasing the quantity of alignment marks. The curvature calculation reveals subtle deformations that linear position measurements cannot detect.
3Measurement precision
If measurement time is increased to improve alignment accuracy, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent applies partial action by calculating curvature only at critical regions or using simplified curvature models that require fewer measurements. Instead of measuring every possible parameter across the entire wafer surface, the system focuses computational effort on extracting the most relevant deformation information from limited measurements, maintaining accuracy while reducing measurement time and preserving throughput.
4Measurement precision
If complex wafer deformation modeling is used to improve alignment accuracy, then measurement precision is improved, but computational complexity increases
Solution Approach 1:
The patent transforms complex spatial deformation patterns into curvature parameters (second derivatives) that can be modeled with simpler mathematical functions. By changing from direct position fitting to curvature-based modeling, the system reduces computational complexity while maintaining or improving alignment accuracy. The curvature values provide a compact representation of wafer deformation that is easier to fit and correct than full spatial maps.
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
Enhances alignment accuracy by deriving more precise wafer deformation information, improving overlay precision without increasing mark density or measurement time, thus optimizing throughput.
Implementation Method 1
an optical system configured to collect radiation that has interacted with an alignment mark on a substrate
Data Source
AI summary
Disclosed is an apparatus for and method of using local alignment position deviation parameters for alignment marks on a semiconductor wafer wherein the parameters are used to generate one or more values indicating a condition of the alignment marks, which values may be used to obtain an wafer grid model having an improved fit.