Lithography Mask CD Measurement Using Aerial Image Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing mask inspection systems for lithography are not suitable for all current or future purposes of use, particularly for single-die masks, and require manual, time-intensive processes that are prone to errors.
Innovation Solution
A method involving the alignment of an aerial image and mask design to determine a CD threshold value and measure critical dimensions, with semi-automatic positioning of regions and automated analysis steps to improve accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual inspection methods are used for single-die masks, then flexibility in analysis is maintained, but measurement time increases and error susceptibility increases
Solution Approach 1:
The inspection system performs self-alignment by automatically determining the position of the first and second inspection targets on the mask and calculating the offset between them. This eliminates the need for manual alignment procedures, allowing the system to autonomously complete the inspection process without operator intervention, thereby reducing inspection time while maintaining measurement accuracy.
Solution Approach 2:
The system pre-positioning of inspection targets and pre-calculated offset values enable rapid inspection execution. By preparing the alignment information in advance through automated target recognition and offset calculation, the system eliminates time-consuming manual alignment steps during the actual inspection process.
2Productivity
If automated inspection systems are used, then inspection speed increases, but adaptability to different mask types decreases
Solution Approach 1:
The inspection method is designed to work universally on single-die masks with different layout configurations. By using two inspection targets that can be positioned at various locations and calculating offsets adaptively, the system maintains high throughput while being able to inspect different mask types and patterns without requiring reconfiguration of the inspection system.
Solution Approach 2:
The system dynamically adjusts the inspection parameters based on the detected positions of the inspection targets. The offset calculation and measurement procedures adapt to the specific location and configuration of targets on different masks, enabling the automated system to maintain both speed and adaptability across various mask types.
3Reliability
If manual alignment is performed, then positioning flexibility is maintained, but measurement reliability decreases due to operator error
Solution Approach 1:
The system automatically performs alignment by detecting the positions of inspection targets and calculating the offset between them without requiring manual intervention. This self-aligning capability eliminates operator-dependent variability and ensures consistent, reliable measurements while simplifying the overall operation to a single automated process execution.
Solution Approach 2:
The manual mechanical alignment process is replaced with an automated optical and computational system. The system uses optical detection to locate inspection targets and computational algorithms to calculate offsets, substituting manual mechanical positioning with automated digital processing that enhances both reliability and ease of operation.
Data Source
AI summary
A method for analysing a mask for lithography, comprising: aligning an aerial image of the mask and a mask design of the mask to form a superimposition of the aerial image and the mask design, wherein a CD threshold value determining region and a CD measuring region are positioned within the aerial image; determining a CD threshold value in the CD threshold value determining region using the superimposition of the aerial image and the mask design; and measuring a critical dimension, CD, in the CD measuring region using the aerial image and the determined CD threshold value. Further disclosed is a corresponding computer program, device and system.