Reversible Scan Chain Defect Diagnosis
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Solution Overview
Problem
Reversible scan chains in integrated circuit defect diagnosis often require laborious and time-consuming physical failure analysis due to the large die area associated with suspected defects, even with U-turn loading and unloading processes.
Innovation Solution
A computing system with an automatic test pattern generation tool generates test patterns for reversible scan chains, allowing serial loading and unloading in multiple directions to identify defect locations, and a defect diagnosis tool detects suspected defects and determines the corresponding direction, narrowing down the inspection area for manufacturing faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If reversible scan chain with U-turn loading and unloading process is used, then defect location identification capability is improved, but physical failure analysis time and effort increases due to large die area
Solution Approach 1:
The patent divides the scan chain into multiple segments or groups, allowing targeted testing of specific regions. By segmenting the scan chain, the system can isolate and identify defective regions more quickly without requiring comprehensive physical failure analysis of the entire large die area, thus reducing analysis time while maintaining identification capability.
Solution Approach 2:
The patent introduces a new dimension to defect diagnosis by implementing bidirectional (forward and reverse) scanning capabilities. This allows the system to approach defect detection from multiple directions, enabling faster localization of defects by comparing results from different scan directions, thereby reducing the time required for physical failure analysis.
2Measurement precision
If reversible scan chain architecture is used to narrow down defect locations, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent implements a universal scan chain architecture that can operate in multiple modes (forward scanning, reverse scanning, selective segment scanning). This multi-functional design allows the same hardware structure to perform various diagnostic functions, improving measurement precision without requiring separate dedicated circuits for each function, thus managing device complexity effectively.
Solution Approach 2:
The patent introduces dynamic control mechanisms that allow the scan chain to adapt its operation based on test requirements. The ability to dynamically switch between forward and reverse directions, and to selectively activate different segments, provides flexible defect localization capability while maintaining a relatively simple base architecture through software-controlled adaptability.
3Reliability
If comprehensive test patterns are applied to entire die area, then defect detection capability improves, but testing time increases
Solution Approach 1:
The patent divides the test process into segments corresponding to different regions or groups of scan cells. Instead of applying comprehensive test patterns to the entire die area at once, the system can selectively apply tests to specific segments, improving defect detection capability for critical regions while reducing overall testing time by avoiding redundant testing of known-good areas.
Solution Approach 2:
The patent implements a strategy where test patterns are applied selectively to suspected or critical regions rather than uniformly across the entire die. This partial action approach focuses testing resources on areas most likely to contain defects, maintaining high defect detection capability while significantly reducing the time required for comprehensive full-die testing.
Data Source
AI summary
This application discloses a computing system implementing an automatic test pattern generation tool can generate test patterns to apply to a reversible scan chain in an integrated circuit. The reversible scan chain can be configured to serially load and unload the test patterns in multiple directions to generate test responses. The computing system can implement a defect diagnosis tool to detect a presence of a suspected defect associated with the reversible scan chain based on the test responses, identify which of the multiple directions used to load and unload the test patterns corresponds to the suspected defect in the reversible scan chain based on the test responses, and determine a portion of the integrated circuit to inspect for a manufacturing fault corresponding to the suspected defect based, at least in part, on the identification of which of the multiple directions corresponds to the suspected defect in the reversible scan chain.