IC Shield Structure with Non-Metallic Portion and Ground Strap
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Solution Overview
Problem
Integrated circuits with inductors on silicon substrates face degradation in quality factor (Q) due to induced eddy currents and power dissipation from electric fields, which existing shield structures fail to adequately address.
Innovation Solution
A shield structure for integrated circuits comprising a non-metallic portion and a metallic ground strap, where the non-metallic portion is arranged to inhibit eddy currents and the metallic ground strap provides efficient grounding, allowing the use of metal layers for both inductor formation and shielding without reducing available metallization levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metallic shield structure is used to provide efficient grounding and high conductivity, then the grounding performance is improved, but eddy currents are induced that degrade the quality factor (Q) of inductors
Solution Approach 1:
The shield structure uses a composite configuration combining metallic ground straps for efficient grounding with non-metallic shield elements (such as doped polysilicon or diffusion regions) that have high electrical resistance. This composite approach allows the metallic portions to provide low-impedance ground connections while the high-resistance non-metallic portions minimize eddy current formation, thereby maintaining both grounding performance and inductor quality factor.
2Reliability
If metal layers are used for shield structure formation, then conductivity is improved, but the number of available metallization levels for inductor formation is reduced
Solution Approach 1:
The shield structure applies local quality by using metallic materials only where high conductivity is critical (ground straps connecting to ground nodes), while using non-metallic high-resistance materials for the shield elements that require electrical isolation. This localized material selection optimizes conductivity where needed while preserving metal layer availability for inductor formation in other areas of the device.
3Loss of energy
If non-metallic materials are used for the entire shield structure, then eddy currents are inhibited and quality factor (Q) is improved, but conductivity and grounding efficiency are reduced
Solution Approach 1:
The shield structure uses a composite configuration combining metallic ground straps for efficient grounding with non-metallic shield elements (such as doped polysilicon or diffusion regions) that have high electrical resistance. This composite approach allows the metallic portions to provide low-impedance ground connections while the high-resistance non-metallic portions minimize eddy current formation, thereby maintaining both grounding performance and inductor quality factor.
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 proposed shield structure enhances the quality factor (Q) of inductors by reducing eddy currents and power dissipation, while maintaining high conductivity and minimizing the use of metallization levels, particularly beneficial for mature technology nodes like 0.25 μm and 0.35 μm.
Implementation Method 1
the shield member comprises a plurality of conductive regions formed from a non-metallic material and arranged substantially to inhibit an inducement of eddy current in the shield member by a current in an inductor disposed adjacent to a shield portion
Implementation Method 2
the ground strap comprises a metallic portion
Data Source
AI summary
A method of forming an integrated circuit is disclosed. The method includes providing a substrate and forming on the substrate a shield structure comprising a shield member and a ground strap. The shield member comprises a non-metallic portion, and the ground strap comprises a metallic portion.