3D Profilometry With Linnik Interferometry for Bond Void Detection
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Solution Overview
Problem
Existing metrology techniques, such as acoustical microscopy and patterned wafer geometry tools, are insufficient in resolution to detect voids and surface imperfections between bonded samples in 3D IC structures, which can cause device failures and interconnect issues due to stringent tolerance requirements.
Innovation Solution
A Linnik interferometer-based metrology system is used to generate volumetric data of bonded samples by scanning along the depth direction, providing faster and more efficient imaging with sub-micron resolution and accuracy, suitable for detecting voids and surface shapes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If acoustical microscopy or patterned wafer geometry tools are used for detecting voids and surface imperfections, then the inspection coverage is achieved, but the resolution is insufficient to meet sub-micron tolerance requirements
Solution Approach 1:
The patent replaces mechanical scanning probe microscopy (AFM) and acoustical microscopy with optical interferometry. The Linnik interferometer uses light waves to create interference patterns that encode surface topography information, achieving sub-micron resolution without mechanical contact or acoustic wave limitations.
Solution Approach 2:
The patent transitions from 2D surface imaging to 3D volumetric imaging by capturing interferometric data at multiple focal planes and reconstructing the complete three-dimensional surface topology. This enables detection of voids and imperfections throughout the bonding interface volume, not just at the surface.
2Productivity
If traditional metrology methods are used for surface characterization, then the measurement process is completed, but the imaging time is too long for efficient production inspection
Solution Approach 1:
The interferometer continuously illuminates the entire field of view with coherent light, capturing all surface information simultaneously in a single exposure. This eliminates the sequential scanning process of AFM, where the probe must physically move across each point, enabling rapid imaging suitable for production inspection.
Solution Approach 2:
The patent combines multiple measurement functions into a single interferometric measurement. The Linnik interferometer simultaneously captures amplitude and phase information, enabling quantitative phase imaging (QPI) that provides both topographic height data and material property information in one operation.
3Measurement precision
If AFM is used for pad shape characterization before bonding, then high resolution surface data is obtained, but the process is slow and not suitable for rapid inspection
Solution Approach 1:
The patent replaces the mechanical scanning probe of AFM with a non-contact optical interferometric measurement system. The Linnik interferometer uses light reflection and interference to measure surface height variations, achieving comparable or superior resolution without the speed limitations of mechanical scanning.
Solution Approach 2:
The interferometer creates an optical copy or holographic record of the surface topology through interference patterns. By capturing the phase information of reflected light waves, the system reconstructs a digital elevation model of the pad surface, enabling rapid characterization without physical contact.
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
The system offers higher resolution and faster imaging times, enabling effective detection of voids and surface imperfections, thereby improving the quality of 3D IC bonding processes.
Implementation Method 1
a beamsplitter configured to split the illumination beam into a measurement beam propagating in a measurement arm and a reference beam propagating in a reference arm
Implementation Method 2
A Linnik interferometer-based metrology system is used to generate volumetric data of bonded samples
Data Source
AI summary
Systems and methods for generating volumetric data are disclosed. Such systems and methods may include scanning a sample at a plurality of focal planes located along a depth direction of the sample. Such systems and methods may include generating, via a detector of a metrology sub-system, a plurality of images of a volumetric field of view of the sample at the plurality of focal planes. Such systems and methods may include aggregating the plurality of images to generate volumetric data of the volumetric field of view of the sample. The metrology sub-system may include a Linnik interferometer.