Pattern Ground Shield for Spiral Inductor Q-Factor
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Solution Overview
Problem
As integrated circuit density increases, noise affects inductors, requiring effective shielding to improve the Q-factor, which is complicated by the need for unidirectional metal and mask coloring in advanced transistor technologies like 7nm gate widths, making traditional pattern ground shield implementation challenging.
Innovation Solution
The implementation of a pattern ground shield in the M0 layer with unidirectional metal traces and a current return path using higher level metals, coupled to a P+ diffusion, reduces parasitic capacitance and enhances the Q-factor of spiral inductors by blocking E-field penetration and preventing conduction current flow, while maintaining noise pickup and shielding functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional pattern ground shield is implemented to shield the inductor from noise, then the Q-factor of the inductor is improved, but the implementation becomes complex due to unidirectional metal and mask coloring requirements in advanced transistor technologies
Solution Approach 1:
The pattern ground shield is segmented into multiple discrete ground connections arranged in a specific pattern beneath the inductor. Instead of using a continuous ground plane, the shield is divided into separate ground pads connected through the substrate, which reduces the complexity of metal routing while maintaining effective noise shielding and preserving the inductor's Q-factor.
2Productivity
If the integrated circuit density is increased to improve productivity, then more circuits can be integrated, but noise affects certain circuits including inductors requiring additional shielding
Solution Approach 1:
The substrate itself is utilized as an intermediary medium to provide ground connections for the pattern ground shield. By leveraging the substrate's inherent grounding properties and creating controlled ground paths through it, the solution provides effective noise shielding for high-density circuits without requiring additional complex shielding structures that would reduce circuit density.
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
This approach improves the Q-factor and self-resonance frequency of spiral inductors, enabling high-speed communication and supporting 7nm and sub-7nm transistor technology, with a higher self-resonance frequency and wider frequency range, critical for advanced communication systems.
Implementation Method 1
block the spiral inductor's E-field from penetrating into the electrically lossy substrate
Implementation Method 2
enables shielding and picking up the substrate noise
Data Source
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AI summary
An integrated circuit device is described. The integrated circuit device comprises a substrate (202); a plurality of metal routing interconnect layers (710, 712, 716); an inductor (108) formed in at least one metal layer of the plurality of metal routing interconnect layers; and a bottom metal layer (702) between the plurality of metal routing interconnect layers and the substrate; wherein a pattern ground shield (302) is formed in the bottom metal layer. A method of implementing an inductor in an integrated circuit device is also disclosed.