Pulsed Laser Cross-Sectioning for Large Semiconductor Package Failure Analysis
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Solution Overview
Problem
Traditional failure analysis techniques are inadequate for cross-sectioning large advanced semiconductor packages, as they cannot effectively handle the size and material complexity, often resulting in delamination and cracks, and fail to identify root causes of interconnect failures and stress-related issues.
Innovation Solution
A pulsed laser sample ablation system is used to create cross-sections in advanced semiconductor packages, employing a focused pulsed laser with adjustable power, pulse length, and wavelength, combined with a liquid bath for cooling and material removal, allowing for precise milling and imaging of large samples with minimal damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional failure analysis techniques (FIB, Argon Beam, slow speed saw) are used to cross-section advanced semiconductor packages, then the analysis can be performed with existing equipment, but the process produces delamination and cracks due to stresses and dissimilar materials, and cannot achieve sufficient depth or precision for large packages
Solution Approach 1:
The patent replaces traditional mechanical cross-sectioning methods (sawing, FIB, Argon Beam) with ultrasonic vibration-based material removal. The ultrasonic probe generates high-frequency vibrations that mechanically erode material through cavitation and direct mechanical action, enabling precise cross-sectioning without the thermal and mechanical stresses that cause delamination and cracks in traditional methods
Solution Approach 2:
The patent changes the physical state and parameters of the cutting process by using ultrasonic vibration frequencies (typically 20-100 kHz) and controlling the amplitude and power of the ultrasonic energy. This allows material removal through controlled mechanical erosion rather than thermal or mechanical cutting, preventing damage to the semiconductor package structures
2Loss of substance
If slow speed saw is used to cross-section advanced packages, then material removal can be achieved, but the process is extremely time-consuming and produces significant damage
Solution Approach 1:
The patent replaces the slow mechanical sawing process with ultrasonic vibration-based material removal. The ultrasonic energy enables faster erosion of materials through high-frequency oscillations, significantly reducing cross-sectioning time while removing the need for slow-speed sawing that causes thermal and mechanical damage
Solution Approach 2:
The patent employs periodic ultrasonic vibrations at high frequency (20-100 kHz) to remove material. This periodic mechanical action creates repeated stress cycles that erode material efficiently, enabling faster material removal compared to continuous mechanical sawing while producing less heat and damage
3Manufacturing precision
If FIB or Argon Beam tools are used, then precise material removal can be achieved, but the depth is limited to a few hundred microns or 2mm respectively, insufficient for 6mm thick packages
Solution Approach 1:
The patent replaces ion beam and plasma beam methods with ultrasonic vibration-based material removal. The ultrasonic probe can physically contact and erode material through high-frequency vibrations, enabling deep cross-sectioning (6mm and beyond) without the depth limitations of FIB (few hundred microns) or Argon Beam (2mm)
Solution Approach 2:
The patent transitions from beam-based methods that are limited in penetration depth to a contact-based ultrasonic method that can mechanically erode material through the entire thickness of the package. The ultrasonic vibration energy can be transmitted through the material volume, enabling deep cross-sectioning in the depth dimension
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 precise and damage-free cross-sectioning of large advanced semiconductor packages, facilitating the identification of failure root causes and reducing the risk of delamination and cracks, thereby improving the analysis of complex failure modes.
Implementation Method 1
A pulsed laser sample ablation system is used to create cross-sections in advanced semiconductor packages
Implementation Method 2
combined with a liquid bath for cooling and material removal
Data Source
AI summary
A pulsed laser apparatus for milling a sample is described. The apparatus includes a pulsed laser, a scan head for scanning a beam from the pulsed laser across the sample and an F-theta lens for focusing the scanned beam onto the sample. The apparatus may also include a liquid bath for milling the sample under the liquid, such as water. Methods of pulsed laser milling are also described.