Orientation Error Detection Using Dual Coordinate Systems
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Solution Overview
Problem
Current methods for determining alignment errors and distortions on substrates, especially in 3D technologies, face challenges in achieving high accuracy and efficiency, particularly as structures become smaller and wafers larger, leading to inaccuracies in alignment and distortion detection.
Innovation Solution
The implementation of two coordinate systems, one for translational and rotary motion of the substrate and optics, and another defined in the computer for structure position fields, allows for efficient and accurate alignment by minimizing detection errors and enabling faster detection through digital image acquisition and software correlation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional alignment methods are used for large wafers with small structures, then the measurement process becomes time-consuming and error-prone, but achieving high alignment accuracy across the entire wafer surface remains necessary
Solution Approach 1:
The wafer surface is divided into multiple measurement fields or zones. The alignment system measures different regions sequentially or in parallel, processing the entire wafer surface by breaking it down into manageable segments. This reduces the time required to measure the entire large wafer while maintaining accuracy across all regions through systematic coverage.
Solution Approach 2:
Alignment marks are pre-defined and stored in a database before the actual measurement process. The system retrieves these pre-stored mark positions and uses them as reference points for rapid measurement. This preliminary preparation enables faster measurement execution without compromising alignment accuracy.
2Manufacturing precision
If alignment marks are used to position structures on the wafer, then alignment can be achieved, but distortion of structures due to processing stresses cannot be detected
Solution Approach 1:
A coordinate system transformation layer is introduced as an intermediary between the alignment marks and the actual structure positions. The system measures the actual positions of structures, transforms these measurements into the alignment mark coordinate system, and compares them with ideal positions. This intermediary transformation enables detection of distortions that would otherwise be invisible when relying solely on alignment marks.
Solution Approach 2:
The system replaces reliance on purely mechanical alignment mark positioning with an optical measurement system that directly measures structure positions. By using optical detection methods instead of depending solely on mechanical alignment references, the system can detect actual structure positions and identify distortions caused by processing stresses.
3Measurement precision
If the wafer surface is measured in detail to detect alignment errors, then accuracy improves, but the complexity of the measurement system increases
Solution Approach 1:
The measurement system is designed with multi-functionality to reduce overall complexity. The same optical system and coordinate transformation algorithms are used for multiple purposes: detecting alignment marks, measuring structure positions, identifying distortions, and generating alignment corrections. This universal approach avoids the need for separate specialized systems for each measurement task.
Solution Approach 2:
The system creates and uses virtual copies of the ideal wafer structure positions stored in a database. By comparing actual measurements against these digital copies or models of the intended structure positions, the system can detect alignment errors and distortions without requiring physical reference standards for every measurement, simplifying the physical measurement system.
4Manufacturing precision
If alignment accuracy is increased to less than 2 μm for all sites on the wafer, then 3D technology requirements are met, but the demands on alignment technology and measurement precision increase greatly
Solution Approach 1:
The system transitions from two-dimensional planar alignment measurements to three-dimensional position detection. By measuring structures at different focal planes and depths, the system can achieve sub-micron accuracy across the entire wafer surface, including the edges. This dimensional extension enables meeting the stringent alignment requirements for 3D technologies.
Solution Approach 2:
The system implements feedback loops where measurement results are continuously compared against ideal positions, and correction information is fed back to the alignment process. This iterative feedback mechanism enables the system to achieve and maintain the high alignment accuracy requirements for 3D technologies by continuously refining measurements and corrections.
Data Source
AI summary
A device for determining alignment errors of structures which are present on, or which have been applied to a substrate, comprising a substrate holder for accommodating the substrate with the structures and detection means for detecting X-Y positions of first markings on the substrate and/or second markings on the structures by moving the substrate or the detection means in a first coordinate system, wherein in a second coordinate system which is independent of the first coordinate system X′-Y′ structure positions for the structures are given whose respective distance from the X-Y positions of the first markings and/or second markings can be determined by the device.