Homogeneous Scan Chain Segmentation for Systematic Defect Isolation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current semiconductor fabrication processes face challenges in efficiently identifying and isolating systematic defects in circuits, particularly in sequential cells, which hinders the detection of process defects and affects the overall quality of semiconductor devices.
Innovation Solution
The method involves forming scan chains with scan cells of the same cell type, applying test patterns, and comparing observed responses to identify defective cells, allowing for the isolation and potential repair of weak sequential cells, thereby facilitating further testing of the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional inspection processes are used to detect defects on wafers, then defect detection is performed, but the ability to efficiently identify and isolate systematic defects in sequential cells is insufficient
Solution Approach 1:
The circuit is divided into multiple scan chains, each containing scan cells of the same cell type. This segmentation allows systematic defects to be isolated to specific cell types and chains, making defect identification more efficient. The patent groups sequential cells into homogeneous scan chains so that when a defect is detected, it can be traced to a specific cell type rather than searching through mixed cell types.
Solution Approach 2:
Each scan chain is designed with uniform local quality by containing only scan cells of the same cell type. This homogeneity within each chain allows for consistent testing conditions and makes it easier to identify systematic defects specific to particular cell types. The patent applies different test patterns to different scan chains based on their cell type characteristics.
2Productivity
If scan chains with mixed cell types are used, then testing can proceed, but defective cells cannot be quickly identified or isolated
Solution Approach 1:
The patent segments scan chains into homogeneous groups based on cell type, allowing parallel testing of multiple chains while maintaining the ability to quickly isolate defects. Each chain can be tested simultaneously, preserving productivity, while the homogeneous structure enables rapid defect identification when failures occur.
Solution Approach 2:
The patent changes the organizational parameter of scan chains from mixed cell types to homogeneous cell types. This parameter change enables both maintained productivity through parallel testing and reduced defect identification time through systematic grouping. Different test patterns are applied to different cell type chains, optimizing detection efficiency.
3Reliability
If systematic defects are not properly isolated, then testing continues, but confidence in defect detection and overall device reliability is reduced
Solution Approach 1:
The patent implements feedback mechanisms where test results from each scan chain are analyzed to identify systematic defects. When defects are detected in specific cell types, this information feeds back into the testing process to adjust test patterns and focus on affected areas. This feedback loop increases confidence in defect detection by systematically tracking and addressing issues.
Solution Approach 2:
The patent uses parameter changes in test patterns applied to different scan chains to enhance defect detection confidence. By varying test parameters based on cell type and detected issues, the system systematically addresses potential defects and builds confidence in the reliability assessment through methodical parameter adjustment and retesting.
Data Source
AI summary
Methods and systems for determining a systematic defect in a circuit under test is provided. Elements of the circuit under test converted into scan cells. A first scan chain that includes a first plurality of scan cells is formed. Each scan cell of the first plurality of scan cells of the first scan chain are of a first cell type. The first scan chain contains a first scan input and a first scan output. A first test pattern is applied at the scan input and a first test output is collected for the applied first test pattern at the first scan output. The collected first test output is compared with a first expected test output. The first cell type is marked to be a suspect for a systematic defect when the first test output is different from the first expected test output.