Comb Test Structure for Localizing Shorts in Metal Interconnect Lines
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for identifying and localizing electrical shorts in semiconductor devices are inefficient and costly, as they often require extensive testing and visualization techniques that are not effective for buried defects or conductive shorts.
Innovation Solution
A test structure and method using a comb-shaped design with pass gates that allow for electrical disconnection of fingers, enabling voltage contrast imaging to localize shorts by identifying which fingers are at the same potential as the affected area, thereby reducing the area that needs to be inspected for defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional electrical continuity testing is used to detect shorts, then defect presence can be determined, but defect location cannot be identified
Solution Approach 1:
The comb structure is divided into multiple individually addressable fingers that can be electrically isolated from each other using pass gates. This segmentation allows the test to identify which specific finger region contains the short circuit defect, transforming a binary pass/fail test into a localized diagnostic tool.
Solution Approach 2:
Pass gates are introduced as intermediary switching elements between the busbar and comb fingers. These pass gates enable selective electrical connection and disconnection of finger segments, allowing the testing apparatus to isolate and identify the specific location of shorts by controlling which regions are electrically active during testing.
2Measurement precision
If extensive milling and visualization techniques are used to find buried defects, then defect causes can be identified, but time and cost increase significantly
Solution Approach 1:
The comb structure with pass gates performs preliminary localization of the short circuit defect before any physical sectioning or advanced visualization is attempted. By electrically isolating and testing individual finger segments, the defect is narrowed down to a specific small region, making subsequent milling and analysis much more efficient and targeted.
Solution Approach 2:
The test structure segments the large area under test into many small, addressable finger regions. This segmentation allows the defect search space to be divided and conquered systematically, reducing the area requiring expensive and time-consuming milling and visualization techniques to only the specific finger containing the defect.
3Measurement precision
If the entire test structure is milled for defect analysis, then all areas can be inspected, but the process is slow and expensive
Solution Approach 1:
The comb structure divides the test area into multiple discrete finger segments that can be independently tested. This allows the testing process to focus only on the specific segment containing the defect rather than milling and inspecting the entire structure, dramatically improving productivity while maintaining inspection thoroughness for the relevant area.
Solution Approach 2:
Instead of performing the excessive action of milling the entire test structure, the invention applies partial action by using electrical testing through pass gates to identify and isolate the specific finger containing the defect. This partial approach achieves sufficient inspection coverage for defect identification without the unnecessary cost and time of complete structural milling.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for faster and more cost-effective localization of electrical shorts, minimizing the need for extensive milling and visualization, and enabling more precise identification of defect causes.
Implementation Method 1
voltage contrast imaging to localize shorts by identifying which fingers are at the same potential as the affected area
Data Source
AI summary
A test structure for localizing shorts in an integrated circuit and method of testing is described. A first comb structure is formed from a first busbar and a first plurality of fingers extending from the first busbar. A second comb structure formed from a second busbar and a second plurality of fingers extending from the second busbar. The second plurality of fingers is interleaved with the first plurality of fingers. A plurality of pass gates is connected between the first plurality of fingers and the first busbar. A pass gate terminal is electrically connected to the gate electrode of each of the plurality of pass gates. When the pass gates are turned OFF thereby disconnecting the first busbar from the first plurality of fingers, voltage contrast imaging can be used to identify which of the first fingers is adjacent the short.