研究目的
To develop an ultrasonic inspection technique using pulse compression for detecting bonding defects in stacked wafers, improving sensitivity over traditional pulse wave methods.
研究成果
The pulse compression method significantly reduces noise by 66% and improves SNR, enabling detection of smaller defects (down to 20 μm) compared to pulse wave methods (100 μm), enhancing ultrasonic image visibility for laminated samples.
研究不足
The technique may be limited by the frequency characteristics of the ultrasonic probe and the complexity of signal processing; further optimization is needed for different sample types and deeper defects.
1：Experimental Design and Method Selection:
Applied pulse compression method with FSK modulation for transmitted signals, designed based on ultrasonic probe frequency characteristics to improve defect detection sensitivity.
2：Sample Selection and Data Sources:
Used a 3-layer stacked sample with silicon wafers and polyimide film, containing artificial square hole defects of sizes from 1 to 100 μm.
3：List of Experimental Equipment and Materials:
Ultrasonic probe with nominal frequency of 200 MHz, measurement sample with specific layers and defects.
4：Experimental Procedures and Operational Workflow:
Performed ultrasonic measurements using C-scan method with 2 μm scanning interval over a 720 μm × 1400 μm area; compared pulse wave and pulse compression methods by computing correlation functions and converting to brightness values.
5：Data Analysis Methods:
Evaluated standard deviation of brightness values and signal-to-noise ratio (SNR) to quantify defect detection sensitivity.
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