Vertical PoP Passive Structures for Higher-Q RF Inductors
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Solution Overview
Problem
Passive devices such as inductors and transformers in RF applications exhibit low Q factors due to Eddy currents in silicon substrates, and their performance is not satisfactory when formed on glass substrates or in fan-out structures of device dies during packaging.
Innovation Solution
A Package-on-Package (PoP) structure is developed with passive devices formed using Through Assembly Vias (TAVs) and Redistribution Lines (RDLs), where TAVs are formed over an adhesive layer and connected by RDLs, and a polymer is molded to fill gaps, allowing for the formation of vertical passive devices with improved Q factors by enclosing more space within the device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive devices are formed in traditional planar structures on silicon substrates, then manufacturing is straightforward, but Q factors are low due to Eddy currents
Solution Approach 1:
The patent transitions from planar passive devices to three-dimensional vertical passive devices by stacking conductive layers and dielectric materials in the vertical dimension. This vertical configuration increases the effective area for magnetic flux containment while reducing the horizontal footprint, thereby improving Q factors without being constrained by substrate plane limitations.
Solution Approach 2:
The patent implements nested magnetic flux containment structures where inner conductive loops are surrounded by outer conductive loops, with dielectric materials nested between them. This nested configuration creates multiple shielding layers that work together to contain magnetic flux and reduce Eddy current losses, significantly improving Q factors.
2Adaptability or versatility
If passive devices are formed on glass substrates or in fan-out structures, then substrate flexibility is improved, but performance remains unsatisfactory
Solution Approach 1:
The patent employs vertical stacking of passive device components in the third dimension, allowing the device to achieve high performance regardless of substrate material. This vertical configuration enables effective magnetic flux containment through stacked conductive layers, making the device performance independent of substrate flexibility characteristics.
Solution Approach 2:
The patent uses composite structures combining multiple conductive materials (such as copper and aluminum layers) separated by dielectric materials (such as silicon dioxide and silicon nitride). This composite approach creates optimized electromagnetic properties that transcend substrate material limitations, achieving high Q factors on various substrate types including glass.
3Reliability
If horizontal package size is increased to improve passive device performance, then Q factors may improve, but package area expands
Solution Approach 1:
The patent achieves high Q factors by utilizing the vertical dimension through stacked conductive loops and dielectric layers. This three-dimensional configuration increases the effective magnetic flux containment volume without expanding the horizontal package footprint, thereby improving performance while maintaining compact form factor.
Solution Approach 2:
The patent implements nested conductive loops where smaller inner loops are surrounded by larger outer loops in the same horizontal plane, with additional loops stacked vertically. This nested configuration maximizes the magnetic flux containment area within a compact horizontal footprint, achieving high Q factors without significant package area expansion.
Data Source
AI summary
A device includes a polymer. A device die is disposed in the polymer. A passive device includes three Through Assembly Vias (TAVs) penetrating through the polymer, wherein the TAVs are coupled in series. A Redistribution Line (RDL) is underlying the polymer. The RDL electrically couples a first one of the TAVs to a second one of the TAVs.