Scan Chain Defect Localization via Control and Observe Groups
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Solution Overview
Problem
Current IC design testing methods face challenges in uniquely localizing multiple scan chain defects per scan chain, especially when multiple scan cells produce similar test responses, making defect localization difficult and incomplete, particularly in early stages of new technology development.
Innovation Solution
The approach involves partitioning scan cells into control and observe groups, applying capture patterns, and solving systems of linear equations to identify potential defect locations, allowing for unique localization of defects by combining outputs from observe groups and using non-overlapping control and observe groups to handle multiple defects per chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If scan cells are not partitioned into control and observe groups, then the testing process is simpler, but defect localization resolution deteriorates when multiple defects exist per scan chain
Solution Approach 1:
The patent divides scan cells into control groups and observe groups, where control groups contain scan cells that receive capture patterns and observe groups contain scan cells that produce observable outputs. This segmentation enables unique identification of multiple defects per scan chain by creating distinct measurement paths, resolving the contradiction between maintaining simple testing processes and achieving high defect localization resolution.
2Reliability
If traditional testing methods are used without control and observe groups, then area overhead is reduced, but defect localization completeness deteriorates
Solution Approach 1:
The patent makes existing scan chain infrastructure multi-functional by enabling it to serve both traditional testing purposes and enhanced defect localization. The control and observe group structure allows the same scan cells to be used for both conventional test pattern application and for generating unique defect signatures, achieving complete defect localization without proportionally increasing area overhead.
3Measurement precision
If multiple scan cells are monitored simultaneously without grouping, then testing speed is maintained, but measurement precision deteriorates due to similar test responses
Solution Approach 1:
The patent adds a grouping dimension to the scan chain structure, organizing scan cells into control and observe groups. This dimensional organization creates unique measurement signatures for different defect locations by controlling which scan cells receive patterns and which produce outputs. The grouping enables simultaneous monitoring of multiple scan cells while maintaining measurement precision through structured observation paths that differentiate defect responses.
Data Source
AI summary
Scan cells of a set of scan chains may be partitioned into at least two control groups of scan cells and at least two observe groups of scan cells. Adjacent scan cells in the set of scan chains may belong to different control groups. Each observe group may include at most one scan cell from each control group, and each control group may include at most one scan cell from each observe group. The control groups and observe groups may be used to perform defect localization on the set of scan chains.