Mask Weak Point Detection via Aerial Image Analysis
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Solution Overview
Problem
Current methods for monitoring photolithography masks in wafer fabrication facilities are inadequate in detecting process window reductions before they affect chip performance, leading to potential device failures due to mask fabrication issues, physical changes during use, and cleaning-induced degradation.
Innovation Solution
A system that utilizes aerial imaging and processing to identify weak points on the mask by analyzing aerial images based on a printability function, detecting local extremum points and crossing points within specific intensity and slope thresholds, and triggering alerts for potential mask errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional mask inspection methods are used, then current monitoring capability is maintained, but the ability to detect process window reductions before they affect chip performance deteriorates
Solution Approach 1:
The system performs preliminary detection of mask weak points by analyzing aerial images against the printability function before actual device failures occur. It identifies local extremum points and crossing points that indicate potential process window reductions, enabling early intervention to prevent yield loss.
Solution Approach 2:
The patent introduces an intermediary analysis layer by comparing aerial images to the printability function and identifying specific mathematical characteristics (local extremum points, crossing points with slope thresholds) that serve as indicators of mask degradation, bridging the gap between raw image data and device performance prediction.
2Loss of time
If mask inspection is performed using existing methods, then current monitoring is maintained, but early warning capability for process window reduction is lost
Solution Approach 1:
The system performs preliminary detection of mask weak points by analyzing aerial images against the printability function before actual device failures occur. It identifies local extremum points and crossing points that indicate potential process window reductions, enabling early intervention to prevent yield loss.
3Reliability
If aerial imaging analysis is implemented to detect weak points, then early warning capability is improved, but system complexity increases
Solution Approach 1:
The system creates a computational copy of the mask's optical response through aerial imaging, allowing virtual analysis of mask characteristics without physical manipulation of the actual mask. This enables repeated measurements and complex analysis while maintaining the same physical mask.
Solution Approach 2:
The patent replaces direct physical inspection methods with optical imaging and computational analysis. Instead of physically examining the mask, the system uses aerial images processed through mathematical comparison with the printability function to identify weak points, substituting mechanical inspection with optical and computational methods.
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
This approach provides early warning of mask misprinting risks, enabling more accurate and timely intervention to prevent device failures and improve fab yield by monitoring mask conditions throughout its lifespan.
Implementation Method 1
A light (typically a 193 nm laser) is projected through the mask traveling through specialized optics that images the desired pattern at wafer plane on the photoresist
Implementation Method 2
A light (typically a 193 nm laser) is projected through the mask traveling through specialized optics that images the desired pattern at wafer plane on the photoresist
Data Source
AI summary
An inspection system, and a computer program product that stores instructions for: obtaining an aerial image of an area of the mask; wherein the aerial image represents an expected image to be formed on a photoresist of an object during a lithography process that involves illuminating the area of the mask, by a lithography tool; wherein the photoresist has a printability threshold; wherein the lithography process exhibits a process window that introduces allowable changes at pixels of the expected image that do not exceed an intensity threshold; and searching for at least one weak point at the area of the mask, which is either a local extremum point of the aerial image spaced apart from the printability threshold by a distance that does not exceed the intensity threshold or a crossing point of the printability threshold and being of a slope that is below a predefined threshold.