Projection Lithography Defect Qualification by Contour Deviation
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Solution Overview
Problem
Existing metrology systems struggle to reproducibly qualify defect structures in lithography masks and wafers, particularly in the absence of a specified target contour, leading to inefficiencies in identifying and documenting deviations.
Innovation Solution
A method that determines a maximum part-field-actual difference as a multiple of the standard deviation of intensity distribution, allowing for reproducible defect qualification, and identifies deviations independently of the target contour shape, using EUV or DUV wavelengths and SEM imaging, with optional target contour specification through simulation or empirical values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a target contour is specified for defect qualification, then measurement precision is improved, but device complexity increases due to the need for simulation or empirical data
Solution Approach 1:
The patent applies preliminary action by specifying target contours in advance through simulation or empirical measurements before actual defect qualification. This allows the system to have predefined reference values ready, improving measurement precision without requiring complex real-time calculations during inspection
Solution Approach 2:
The patent uses copying by creating target contours from simulated images of defect-free structures or empirical measurements. These copied reference contours serve as the basis for comparison during defect qualification, enabling accurate defect detection without requiring complex physical reference samples
2Ease of operation
If defect qualification is performed without target contour specification, then ease of operation is improved, but measurement precision deteriorates
Solution Approach 1:
The patent applies self-service by enabling the system to automatically generate or retrieve target contours without requiring manual specification by the operator. The system can use simulated images or empirical data to create reference contours automatically, maintaining ease of operation while ensuring measurement precision through the use of these automatically generated references
3Adaptability or versatility
If the defect qualification method is made generally applicable to different target contours, then adaptability is improved, but difficulty of detecting and measuring increases
Solution Approach 1:
The patent applies universality by creating a defect qualification method that can handle various target contour types (circular, rectangular, irregular) through a unified approach. The system uses general-purpose target contour specifications that can be applied across different structure types, improving adaptability while maintaining consistent measurement procedures that do not require specialized handling for each contour type
Data Source
AI summary
To qualify a defect structure on an object utilizable in projection lithography, a target contour of at least one structure to be measured is first specified on the object. Furthermore, an actual contour of the structure is measured. A deviation between the target contour and the actual contour is determined perpendicularly to the profile of the target contour. A specified value of the determined deviation is documented as a defect qualification parameter of the structure to be measured. A further qualification method can dispense with a specified target contour. The respective qualification method enhances the significance of a defect qualification, which can be carried out in particular with a metrology system.