On-Chip Inductor Air-Gap Isolation for Higher Q in Limited Area
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Solution Overview
Problem
The challenge in semiconductor device fabrication is to balance the size of on-chip inductors with their quality factor, as increasing the quality factor often requires larger inductor sizes, which is undesirable.
Innovation Solution
The introduction of sealed cavities with air gaps in the semiconductor substrate beneath the inductor windings, which reduces energy loss to the substrate and enhances the quality factor without increasing the physical size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the inductor size is increased to improve quality factor, then energy loss to substrate is reduced, but the area occupied on the chip increases
Solution Approach 1:
The substrate is segmented into multiple sealed cavities with air gaps beneath the inductor windings. This segmentation creates isolated regions that prevent energy loss to the substrate while maintaining a compact inductor footprint, resolving the contradiction between reducing energy loss and minimizing area occupation.
Solution Approach 2:
Air gaps are introduced as an intermediary medium between the inductor windings and the semiconductor substrate. These air gaps act as electrical isolators that reduce energy loss to the substrate without requiring the inductor to occupy additional chip area, thus resolving the technical contradiction.
2Loss of energy
If sealed cavities with air gaps are introduced to reduce energy loss, then quality factor is improved, but device complexity increases
Solution Approach 1:
The semiconductor substrate is transformed into a porous structure with sealed cavities containing air gaps. This porous configuration reduces energy loss to the substrate while maintaining manufacturability through standard semiconductor fabrication processes, balancing quality factor improvement with acceptable device complexity.
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 air gaps within the sealed cavities improve the inductor's quality factor by minimizing energy losses, optimizing performance without violating design rules.
Implementation Method 1
Inductors with airgap electrical isolation
Data Source
AI summary
Structures including an inductor and methods of forming such structures. The structure comprises a semiconductor substrate including a first plurality of sealed cavities and a back-end-of-line stack on the semiconductor substrate. Each sealed cavity includes an air gap, and the back-end-of-line stack includes an inductor having a winding that overlaps with the sealed cavities.