IR Alignment Markers for Pre-Reflow Multi-Die Placement
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Solution Overview
Problem
Existing semiconductor manufacturing processes face challenges in accurately aligning multiple dies during assembly, particularly in flip-chip electronic modules, leading to potential misalignment that is irreversible and results in significant cost and yield loss.
Innovation Solution
A system and method utilizing infrared (IR) light inspection with geometric-shaped alignment markers on dies and substrates, allowing for precise alignment verification before solder reflow, using an IR camera to detect alignment and prevent irreversible misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional alignment verification methods are used, then the manufacturing process is simpler, but the alignment precision deteriorates leading to irreversible misalignment after reflow
Solution Approach 1:
The patent replaces traditional mechanical/optical microscopy alignment verification with infrared imaging technology. The infrared camera captures thermal radiation from alignment markers on the die and substrate, enabling non-contact, high-precision alignment verification without the complexity of mechanical measurement systems.
Solution Approach 2:
The patent utilizes thermal radiation detection where alignment markers appear as distinct thermal signatures in the infrared image. The contrast between the alignment markers and the surrounding structures enables precise location detection through thermal contrast rather than visual color or optical reflection differences.
2Reliability
If alignment verification is performed early before reflow, then misalignment can be detected and prevented, but the manufacturing process time increases
Solution Approach 1:
The patent performs alignment verification using infrared imaging immediately after die placement and before the reflow process. This preliminary inspection allows detection and correction of alignment issues while the die is still accessible, preventing irreversible misalignment without requiring extensive additional processing time.
Solution Approach 2:
The infrared alignment verification process operates rapidly, capturing thermal images and calculating alignment status in seconds. The system quickly determines whether alignment specifications are met and whether reflow should proceed, minimizing the time added to the manufacturing process while ensuring reliability.
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
Ensures accurate alignment of dies to substrates, reducing yield loss and module failure by detecting misalignment early in the process, enabling automated and manual verification of alignment accuracy.
Implementation Method 1
an infrared light source providing incident IR light upon the assembly; an IR camera for obtaining images based on IR light reflected from the assembly
Data Source
AI summary
A top-down inspection system and method employs a strategy using specific geometric shaped metal alignment markers on a semiconductor die and a laminate that can be inspected using an IR camera. The metal alignment markers will align at room temperature to assess the die alignment prior to reflowing it. As silicon is transparent to IR wavelengths the system allows for the IR light to pass through the die to the laminate to see alignment features on the die and the laminate concurrently. The specific markers are placed in at least two separate locations preferably >0.5*die size apart. The robust alignment markers are substantially resistant to degradation caused by semiconductor device fabrication steps. The metal alignment markers can be small geometrical shapes to provide a more symmetrical signal which is more resistant to variability in prior processing steps than the standard marker design.