Semiconductor Die Pattern Inspection via Pitch Deviation Normalization
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Solution Overview
Problem
Existing inspection methods for semiconductor die patterns fail to detect small defects due to 'pitch walking' errors, where the pitch of feature arrays is not constant across a wafer, masking these defects in comparisons between dies or with design intent patterns.
Innovation Solution
A method that determines deviations from the nominal pitch in printed patterns on semiconductor dies by comparing them to versions with similar pitch deviations, either within die-to-die comparisons or to a reference pattern with adjusted features, allowing for the detection of pitch errors and smaller defects like mask or process defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inspection is performed by comparing printed patterns with design intent patterns or between dies with different pitch deviations, then defect detection sensitivity is reduced due to pitch walking errors, but manufacturing precision is maintained through standard lithography processes
Solution Approach 1:
The method performs preliminary measurement of pitch deviations on the die under inspection before conducting the defect detection comparison. This preliminary action allows the system to compensate for pitch walking errors by adjusting the reference pattern or selecting a matching comparison die, thereby improving defect detection sensitivity without requiring complex real-time corrections during the inspection process
Solution Approach 2:
The patent introduces an intermediary step of measuring and characterizing pitch deviations as a separate parameter. This intermediary measurement acts as a mediator that enables the system to account for pitch walking effects during subsequent defect detection, allowing sensitive defect identification while working within existing lithography manufacturing processes
2Reliability
If pitch deviations are not compensated for in pattern comparisons, then inspection process remains simple and fast, but small defects are masked and undetected
Solution Approach 1:
Pitch deviation measurements are performed as a preliminary step before defect detection. By measuring pitch deviations upfront and using this information to guide the comparison process, the method ensures reliable defect detection while minimizing additional inspection time through efficient use of the measured data
Solution Approach 2:
The method changes the reference parameter from a fixed design intent pattern to a dynamically adjusted reference that accounts for measured pitch deviations. This parameter adjustment allows the inspection to maintain high reliability by compensating for pitch walking, while the change is implemented through computational adjustment rather than physical re-measurement, reducing time loss
Data Source
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AI summary
The present invention is related to a method for detection of defects in a printed pattern of geometrical features on a semiconductor die, the pattern comprising an array of features having a nominal pitch, comprising the steps of : • determining deviations from the nominal pitch in the printed pattern, • comparing the printed pattern with another version of the pattern, the other version having the same or similar pitch deviations as the printed pattern. According to various embodiments, the other version of the pattern may a printed pattern on a second die, or it may be a reference pattern, obtained by shifting features of the array in a version having no or minimal pitch deviations, so that the pitch deviations in the reference pattern are the same or similar to the pitch deviations in the printed pattern under inspection.