Automated Scan Chain Diagnostics Using Emission Signatures
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Solution Overview
Problem
Current scan chain diagnostics suffer from low resolution, inability to identify logic equivalent gates, and lengthy diagnostic times, with human interpretation challenges due to complex circuit layouts and emission image quality.
Innovation Solution
An automated method and system that register an image of a device under test to a design layout, segmenting pixels to compare actual emission signatures with expected signatures, determining defects, and using binary search to locate specific failures in the scan chain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If emission-based diagnostics are used to increase diagnostic resolution, then measurement precision is improved, but loss of time increases significantly
Solution Approach 1:
The patent segments the emission image into multiple regions corresponding to different scan chain locations and compares each region's emission signature against expected values. This segmentation allows parallel processing of multiple diagnostic locations, reducing total diagnostic time while maintaining gate-level resolution through systematic comparison of segmented regions.
Solution Approach 2:
The patent performs preliminary actions by pre-calculating expected emission signatures for each scan chain location and storing them in a lookup table. During actual diagnostics, these pre-computed signatures are quickly compared against measured emissions, eliminating the need for real-time complex calculations and significantly reducing diagnostic time while preserving measurement precision.
2Ease of operation
If human operators interpret emission images, then ease of operation is maintained, but productivity decreases due to interpretation challenges and subjectivity
Solution Approach 1:
The patent implements self-service by enabling the emission image data to automatically compare itself against expected signatures and identify defects without human intervention. The system performs autonomous analysis by calculating emission signatures for each scan chain location, comparing them to stored expected values, and automatically identifying discrepancies, thereby eliminating operator subjectivity and increasing productivity.
Solution Approach 2:
The patent replaces the mechanical human interpretation process with an automated computational system. Instead of operators visually analyzing emission images, the system uses algorithms to automatically compare measured emission signatures against expected values, perform statistical analysis, and identify defects, thereby eliminating human limitations and significantly improving diagnostic throughput.
3Ease of operation
If tester-based scan chain diagnostics are used, then ease of operation is maintained, but measurement precision deteriorates due to limited resolution
Solution Approach 1:
The patent segments the scan chain into multiple testable locations corresponding to individual gates or transistor regions. By dividing the scan chain into discrete, identifiable segments and analyzing emission signatures for each segment independently, the system achieves gate-level or even transistor-level resolution while maintaining ease of operation through automated analysis of each segment.
Solution Approach 2:
The patent introduces a new dimension of analysis by mapping emission image data onto the physical layout geometry of the scan chain. This spatial mapping allows the system to translate emission measurements into precise physical locations, achieving high measurement precision for defect localization while maintaining operational simplicity through automated coordinate transformation and comparison.
Data Source
AI summary
A method for automated scan chain diagnostics includes comparing actual emission signatures for individual design elements to expected emission signatures, the individual design elements having pixels allocated thereto associated with an image of a device registered to a design layout, and determining whether the actual emission signatures differ from the expected emission signatures by more than a threshold amount to determine if a defect is present.