Modulated Process Window Qualification Layouts for Semiconductor Inspection
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Solution Overview
Problem
Current semiconductor inspection methods, such as optical and SEM-based processes, face challenges in distinguishing defects from noise, especially in identifying systematic defects related to subtle pattern variations. The existing PWQ layout generates a high number of nuisance defects, requiring extensive review to identify true weak points and patterns of interest.
Innovation Solution
The proposed method involves irradiating a reticle or mask with varying lithographic operating variables like focus, energy, and overlay, and recording these patterns on a wafer. This approach allows for the identification of pattern anomalies and defects by comparing spatial patterns across different modulation conditions, thereby reducing noise and improving defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional PWQ layout is used to identify systematic defects, then defect detection capability is improved, but the number of nuisance defects increases requiring extensive review
Solution Approach 1:
The wafer is divided into multiple modulation bins, each representing different process window conditions. This segmentation allows systematic defects to be isolated and identified within specific bins while excluding nuisance defects from other bins, thereby improving inspection efficiency by focusing review efforts only on relevant defects.
Solution Approach 2:
Different regions of the wafer are subjected to different modulation conditions tailored to their specific process window characteristics. This local quality approach enables optimized defect detection for each region while reducing false positives from nuisance defects in other regions, improving overall inspection productivity.
2Measurement precision
If high modulation is applied to amplify weak structures, then detection sensitivity is improved, but the number of nuisance events increases
Solution Approach 1:
The modulation process is segmented into discrete bins with controlled modulation levels. By segmenting the modulation process, the system can apply high modulation only where necessary to amplify weak structures while limiting the propagation of nuisance events to specific bins, thereby maintaining detection sensitivity while reducing overall nuisance event count.
Solution Approach 2:
The patent converts the harmful effect of high modulation generating nuisance events into a beneficial process by using those same high modulation conditions to amplify weak structures and systematic defects. The nuisance events from high modulation in one bin become useful for detecting systematic defects in that specific process window condition.
3Measurement precision
If multiple inspection iterations are performed to increase sensitivity, then defect detection accuracy is improved, but the time required for inspection increases
Solution Approach 1:
The patent performs preliminary action by conducting focus-exposure matrix inspection and initial PWQ inspection before the main inspection process. This preliminary inspection identifies systematic defects and process window conditions in advance, allowing the main inspection to focus only on relevant areas and reduce the number of required iterations, thereby decreasing total inspection time while maintaining accuracy.
Solution Approach 2:
The inspection process incorporates feedback mechanisms where results from initial inspection iterations are used to adjust and optimize subsequent inspection parameters. This feedback loop allows the system to reduce the number of required iterations by learning from previous results, thereby decreasing inspection time while maintaining high defect detection accuracy.
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 method enhances the sensitivity of defect detection, reduces the number of nuisance events, and allows for more accurate process window identification, thereby improving the efficiency of semiconductor inspection and review processes.
Implementation Method 1
irradiating a reticle or a mask containing a design pattern. Each of the occurrences of irradiation represents a value of a member of a set of lithographic operating variables
Data Source
AI summary
Process window qualification (PWQ) layouts can be used to determine a presence of a pattern anomaly associated with the pattern, patterning process, or patterning apparatus. For example, a modulated die or field can be compared to a slightly lower offset modulated die or field. In another example, the high to low corners for a particular condition or combination of conditions are compared. In yet another example, process modulation parameters can be used to estimate criticality of particular weak points of interest.