Reticle Inspection Using Reduced Design Database
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Solution Overview
Problem
Conventional reticle inspection techniques often fail to accurately detect defects while also capturing a high number of false defects due to inappropriate threshold settings, leading to inefficiencies in semiconductor manufacturing.
Innovation Solution
A method and system for reticle inspection using a reduced design database that includes maps of nonprintable features and cell-to-cell regions, generated from reticle design data, which is used to inspect reticles in a wafer fabrication facility, reducing storage and bandwidth requirements and enhancing defect detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional inspection techniques use a single threshold value for all reticle regions, then the inspection process is simple to implement, but it results in high false defect detection rates and reduced measurement precision
Solution Approach 1:
The patent applies local quality by dividing the reticle into multiple regions (e.g., first region and second region) and assigning different threshold values to each region based on its specific characteristics. This allows each region to be inspected with an optimized threshold, improving defect detection accuracy while managing complexity through systematic regional classification.
Solution Approach 2:
The inspection process is segmented into multiple steps: dividing the reticle into regions, determining characteristics of each region, selecting appropriate threshold values for each region, and performing inspections accordingly. This segmentation transforms a single complex threshold selection problem into multiple manageable regional inspection tasks.
2Measurement precision
If the inspection threshold is set low to capture small defects, then measurement precision improves, but the number of false defects increases significantly
Solution Approach 1:
Different regions of the reticle are assigned different threshold values based on their local characteristics. Regions prone to false defects use higher thresholds, while regions requiring sensitive defect detection use lower thresholds. This localized approach allows small defects to be detected in appropriate regions without triggering false alarms in other regions.
Solution Approach 2:
The threshold parameter is changed dynamically based on regional characteristics rather than using a fixed value. The system determines specific threshold values for different regions by analyzing regional features, allowing the inspection parameters to adapt to local conditions and optimize both sensitivity and reliability.
3Reliability
If the inspection threshold is set high to reduce false defects, then reliability improves, but small defects are missed and measurement precision deteriorates
Solution Approach 1:
The patent implements local quality by allowing different regions to have different threshold settings. Regions where false defects are common can use higher thresholds for reliability, while regions where small defects are critical can use lower thresholds for precision, thus resolving the trade-off locally rather than globally.
4Measurement precision
If full design database is used for reticle inspection, then defect detection accuracy is maximized, but storage requirements and bandwidth consumption increase significantly
Solution Approach 1:
The patent extracts only the essential features and characteristics needed for inspection from the complete design database, creating a reduced inspection database. This extraction process removes unnecessary data while retaining the critical information required for accurate defect detection, thereby reducing storage and bandwidth requirements.
Solution Approach 2:
Instead of using the full design database, the system creates a simplified copy or representation containing only the necessary inspection data. This copied structure maintains the essential geometric and feature information needed for defect detection while occupying significantly less storage space and requiring less bandwidth for transmission.
Data Source
AI summary
A method embodiment includes providing a reticle design data that specify a plurality of printable features that are formed on the wafer using the reticle and a plurality of nonprintable features that are not formed on the wafer using such reticle, wherein the reticle design data is usable to fabricate the reticle. A reduced design database is generated from the reticle design data and this reduced design database includes a description or map of the nonprintable features of the reticle, a description or map of a plurality of cell-to-cell regions of the reticle, and a grayscale reticle image that is rasterized from the reticle design data. The reduced design database, along with the reticle, is transferred to a fabrication facility so that the reduced design database is usable to periodically inspect the reticle in the fabrication facility.