Semiconductor Failure Analysis Using Multi-Level Voltage Contrast
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Solution Overview
Problem
Existing semiconductor device failure analysis methods require a non-defective reference for comparison, which is not feasible when only defective products are available, and cannot detect disconnection or short-circuit defects at the gate electrode or drain region of MOS transistors due to similar voltage contrast readings with non-defective products.
Innovation Solution
A method and apparatus that acquire a voltage contrast image of a conductive layer by charging and irradiating it with charged particles, search for wiring end points, set multiple brightness levels, and associate these levels with the end points to determine consistency, allowing for the identification of defective positions without a non-defective reference and detecting disconnection or short-circuit defects by comparing voltage contrasts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a non-defective reference sample is used for comparison in voltage contrast imaging, then defect detection is enabled, but the method becomes inapplicable when only defective products are available
Solution Approach 1:
The patent creates a simulated reference image by processing the actual defective sample image through image processing techniques. Instead of requiring a physical non-defective reference sample, the system generates a virtual reference that represents what the image should look like without defects, enabling defect detection directly from production line samples.
Solution Approach 2:
The system performs self-diagnosis by comparing the actual image against a reference derived from the same sample through image processing. The defective sample itself provides the basis for creating the reference, eliminating the need for external reference samples and enabling autonomous defect detection.
2Device complexity
If binary contrast levels (high/low) are used in voltage contrast imaging, then simple defect detection is achieved, but disconnection and short-circuit defects at gate electrode or drain region cannot be detected
Solution Approach 1:
The patent extends the contrast analysis from binary (high/low) to multi-level brightness classification. By dividing the brightness range into multiple levels and assigning different expected levels to different wiring end point types (drain region, gate electrode, substrate), the system can detect subtle variations in voltage contrast that indicate different defect types while maintaining systematic analysis.
Solution Approach 2:
The patent applies different brightness level expectations to different local regions based on wiring end point types. Instead of using a uniform threshold, the system tailors the reference brightness levels to the specific characteristics of each wiring end point location, enabling accurate detection of defects at gate electrodes and drain regions that have distinct electrical characteristics.
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
Enables the identification of defective positions in semiconductor devices using a single defective sample and detects disconnection or short-circuit defects that were previously undetectable, improving the accuracy and efficiency of failure analysis.
Implementation Method 1
the exposed conductive layer is next irradiated with charged particles by an electronic beam. Secondary electrons are released from the semiconductor device, and a voltage contrast image formed thereby is observed
Data Source
AI summary
A semiconductor device failure analysis method and apparatus and a computer program for the method and apparatus are provided. The method includes: an observation image acquisition process of acquiring a voltage contrast image by charging an exposed conductive layer of a semiconductor device and irradiating the exposed conductive layer with charged particles; a wiring search process of searching for end points connected to the conductive layer based on design data; and a determination process of comparing voltage contrasts of three levels or more set in advance, one of which is set for a wiring depending on a state of an end point of the wiring, with the voltage contrast image acquired in the observation image acquisition process to determine consistency/inconsistency. Since three or more levels are set, for example, a short-circuit formed by a conductive layer connected to a transistor diffusion layer and another wiring can be identified.