Panel Embedded Die Inspection Using Combined Thermal and Optical Imaging
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Solution Overview
Problem
Current inspection methods struggle to detect structural defects, such as microcracks, in embedded semiconductor dies due to limitations in resolution and the inability to distinguish between deep cracks and surface scratches, especially after the dies are coated with opaque or optically scattering materials.
Innovation Solution
A multi-modal inspection system comprising a thermal subsystem and an optical subsystem, where the thermal subsystem uses a laser to generate heat and a thermal camera to capture images, while the optical subsystem uses various illumination modalities and a detector to capture images, with a processor to compare images and determine the presence of both surface and bulk defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional optical inspection is used to detect microcracks, then surface defects can be detected, but deep bulk defects cannot be distinguished from surface scratches and detection precision deteriorates
Solution Approach 1:
The patent transitions from 2D optical imaging to 3D thermal imaging by detecting temperature distributions at different depths. The optical coherence tomography technique captures reflectivity signals from different depths within the semiconductor device, creating depth-resolved images that reveal bulk defects beneath the surface that traditional 2D optical inspection cannot detect.
Solution Approach 2:
The patent introduces thermal imaging as an intermediary technique between optical inspection and physical sectioning. By using temperature distribution as a mediator, the system can indirectly visualize internal bulk defects without requiring physical cutting or destructive analysis, preserving the integrity of the device while obtaining depth information.
2Reliability
If optical inspection is performed after coating with opaque or optically scattering materials, then surface protection is provided, but detection capability is lost
Solution Approach 1:
The patent creates a multi-functional inspection system that can operate through opaque and optically scattering coatings. The thermal imaging component detects temperature distributions caused by laser heating, which can penetrate coatings that block visible light. This allows the same inspection system to function both before and after coating applications, maintaining universal applicability across different manufacturing stages.
Solution Approach 2:
The patent replaces optical detection mechanisms with thermal detection mechanisms. Instead of using light to probe defects (which is blocked by opaque coatings), the system uses laser heating followed by thermal imaging to detect defects. This substitution of detection physics allows inspection to proceed through materials that are opaque to visible light but transparent to thermal radiation.
3Measurement precision
If higher resolution optical systems are used to detect smaller cracks, then detection precision improves, but the system cannot distinguish deep cracks from surface scratches
Solution Approach 1:
The patent adds the depth dimension to defect characterization by using optical coherence tomography and thermal imaging. These techniques measure the optical path length or temperature distribution at different depths, allowing the system to distinguish whether a detected feature is a surface scratch or a deep bulk crack, in addition to measuring its lateral dimensions.
Solution Approach 2:
The patent segments the inspection process into surface inspection (optical microscopy for surface scratches) and bulk inspection (optical coherence tomography and thermal imaging for deep cracks). By dividing the inspection task into depth-specific segments, the system can apply the most appropriate technique for each depth zone, maintaining high precision for both surface and bulk defect detection.
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 effectively detects both surface and bulk defects in embedded semiconductor dies, even after coating, by utilizing thermal imaging to identify bulk defects and optical imaging to detect surface defects, thereby improving yield and reliability in semiconductor manufacturing.
Implementation Method 1
a first laser light source configured to emit laser light; a first focusing lens configured to direct the laser light from the first laser light source onto a workpiece
Implementation Method 2
a thermal camera configured to capture a thermal image of the workpiece
Implementation Method 3
at least one light source configured to emit light with at least one illumination modality; a light focusing lens configured to direct the light from the at least one light source onto the workpiece; and a detector configured to capture at least one image of the workpiece
Data Source
AI summary
The system includes a thermal subsystem, an optical subsystem, and a processor. The thermal subsystem comprises a first laser light source configured to emit laser light, a first focusing lens configured to direct the laser light onto a workpiece, and a thermal camera configured to capture a thermal image of the workpiece. The optical subsystem includes at least one light source configured to emit laser light with at least one illumination modality, at light focusing lens configured to direct the light onto the workpiece, and a detector configured to capture at least one image of the workpiece. The processor is configured to compare the at least one image received from the detector to at least one reference image for registration of the workpiece or to determine presence of a surface defect on the workpiece, and to determine presence of a bulk defect in the workpiece based on the thermal image.