Multi-Plane Optical Measurement for Through-Silicon Via Boundary Detection
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Solution Overview
Problem
The high depth-width ratio of through-silicon vias in IC packaging makes it difficult to accurately measure the depth and sidewalls using optical microscopes, necessitating a specialized measurement system and method to capture precise boundary measurements.
Innovation Solution
A measurement system comprising a light source generation unit, a capturing unit, and a processing unit that focuses a light source on multiple height planes of a hole, captures images, samples image intensities at different azimuth angles, and develops a sidewall image by combining these values with height and angle data to determine the hole boundaries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical microscope is used to measure through-silicon vias, then the measurement process is simple, but the measurement precision is insufficient due to high depth-width ratio
Solution Approach 1:
The measurement process is segmented into multiple focal planes along the height axis of the hole. The light source is focused on different height planes sequentially, and images are captured at each plane. This segmentation allows the system to measure the entire depth of the high aspect ratio hole by dividing it into measurable sections, thereby achieving precise boundary measurement without requiring a single complex high-magnification objective.
Solution Approach 2:
The measurement approach transitions from a single-plane 2D measurement to a multi-plane 3D measurement. By introducing the height axis dimension and capturing images at multiple focal planes, the system can reconstruct the complete boundary information of the hole including sidewalls and depth, overcoming the limitation of conventional optical microscopes that can only measure at a single focal plane.
2Length of moving object
If standard optical microscopy is used, then the device complexity is low, but the ability to measure deep holes is insufficient
Solution Approach 1:
The measurement system employs dynamic focusing along the height axis, where the focal plane is moved to different positions to capture images at various depths. This dynamic adjustment of the focal plane allows the system to measure the entire depth of the hole by sequentially imaging different sections, thereby extending the measurable depth beyond the limited depth of field of a single optical objective.
3Measurement precision
If multiple height planes are measured, then the measurement precision improves, but the measurement time increases
Solution Approach 1:
The measurement process continuously captures images at multiple focal planes without interruption, maintaining the useful action of light interaction with the sample throughout the depth range. This continuous measurement approach efficiently collects boundary information from all height planes in a single operational sequence, minimizing measurement time while achieving comprehensive boundary precision.
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 accurate measurement of hole boundaries in through-silicon vias, improving the yield rates of ICs by providing a method to measure structures that are otherwise inaccessible to standard optical microscopes.
Implementation Method 1
a light source generation unit (110), a capturing unit (120)... The light source generation unit is used to generate a light source and focus the light source, respectively, on a plurality of different height planes of a hole
Implementation Method 2
The capturing unit captures a plurality of images scattered by the plurality of different height planes
Data Source
AI summary
A measurement system is provided to measure a hole of a target, including a light source generation unit, a capturing unit and a processing unit. The light source generation unit generates a light source and focuses the light source on a plurality of different height planes. The capturing unit captures a plurality of images scattered from the plurality of different height planes. The processing unit obtains boundaries of the hole on the plurality of different height planes according to the plurality of images, samples image intensities of different azimuth angles on the boundaries of the hole on each of the plurality of different height planes to generate a plurality of sampling values, and develops a sidewall image of the hole according to the plurality of sampling values, the plurality of different height planes and the different azimuth angles.