Locating nA Metal Short Circuits via Resistance Ratio and Voltage Contrast
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Solution Overview
Problem
Conventional failure analysis methods struggle to accurately position nano-sized metal short circuit failures in semiconductor devices due to their low leakage current, making it difficult to determine the exact failure point, especially in advanced semiconductor processes.
Innovation Solution
A method combining resistance ratio analysis and voltage contrast analysis, along with dichotomy, to progressively isolate and locate the short circuit point between metal wires by measuring resistance and performing voltage contrast imaging, allowing for precise identification of the defect location.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional positioning methods (EMMI, OBIRCH, Thermal) are used, then the analysis process is simple and equipment is available, but the leakage current of metal short circuit failures is too small (nA level) to be detected accurately
Solution Approach 1:
The patent replaces conventional optical/thermal detection methods with electrical measurement methods. Specifically, it uses resistance measurement and voltage contrast analysis to detect metal short circuit failures, substituting the mechanical/optical detection systems (EMMI, OBIRCH, Thermal) with electrical measurement systems that can detect nA level leakage currents through resistance ratios and voltage contrasts in metal wire structures.
Solution Approach 2:
The patent changes the detection parameter from optical/thermal signals to electrical parameters (resistance and voltage). By measuring resistance ratios between different metal wires and analyzing voltage contrasts, the method transforms the detection approach to parameters that are sensitive to nA level leakage currents, enabling accurate positioning of metal short circuit failures that are invisible to conventional methods.
2Measurement precision
If OBIRCH is used to position short circuit defects, then the defects can be located, but a long hot spot containing the short circuit position is highlighted instead of only the exact short circuit position
Solution Approach 1:
The patent applies segmentation by dividing the metal wire structure into separate testable segments (first metal wire, second metal wire, third metal wire) with isolated test regions. By measuring resistance ratios between these segmented wires and performing voltage contrast analysis on specific segments, the method narrows down the hot spot area to the exact short circuit position rather than displaying a long hot spot, thus improving positioning precision while managing analysis complexity through systematic segmentation.
Solution Approach 2:
The patent implements local quality by designing test structures with specific local characteristics (comb-shaped metal wires with fingers, isolated test regions) that enhance the visibility and measurability of local defects. The voltage contrast analysis focuses on local voltage differences at potential defect locations, and the resistance ratio measurements target specific local segments, allowing precise localization without requiring complex global analysis.
3Measurement precision
If Thermal method is used, then both previous and latter defects can be positioned, but the heat released from leakage position must reach several tens or hundreds of mW which is not satisfied by nA level short circuit
Solution Approach 1:
The patent replaces the thermal detection system with an electrical measurement system. Instead of requiring tens or hundreds of mW heat release to detect defects thermally, the method uses resistance measurement and voltage contrast analysis that can detect nA level leakage currents. This substitution eliminates the high energy requirement by using electrical parameters that are inherently sensitive to low-level leakage without requiring significant power dissipation.
Solution Approach 2:
The patent changes the detection parameter from thermal energy (mW level heat release) to electrical parameters (resistance and voltage). By measuring resistance ratios and voltage contrasts in the metal wire structure, the method detects nA level leakage currents that would not generate sufficient heat for Thermal method detection, thus reducing the energy requirement from tens/hundreds of mW to nA level power consumption.
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 method effectively positions metal short circuits with nA level leakage, enabling accurate analysis of defects and improving semiconductor process yield by pinpointing the failure cause.
Implementation Method 1
measuring a resistance between the first metal wire and the second metal wire, and positioning the first region where the short circuit point is located by a resistance ratio
Implementation Method 2
performing a voltage contrast analysis on the first metal wire and the plurality of fingers of the second metal wire, and positioning a shape part where the short circuit point is located
Data Source
AI summary
The present invention provides a method for positioning short circuit failure, used to position the short circuit point between a first metal wire and a second metal wire. The positioning method comprises: measuring the resistance between the first metal wire and the second metal wire, and positioning the first region where the short circuit point is located by a resistance ratio. In the first region, the short circuit point may be gradually approached by periodically cutting the first metal wire and the second metal wire, electrically isolating the cut portions, and performing a plurality of voltage contrast analysis on the first metal wire and the second metal wire based on the principle of the dichotomy, thereby accurately locating the short circuit point. With the positioning method provided by the present invention, the region where the short circuit defect of the nA (nano ampere) level is located may be accurately found from the first metal wire and the second metal wire that are extremely long. The present invention contributes to improving the yield of a semiconductor device based on the defect adjustment process.