Discontinuous Guard Ring for Noise Isolation in Mixed-Signal ICs
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Solution Overview
Problem
Mixed signal integrated circuit (IC) chips face noise interference issues due to the proximity of noisy digital circuit blocks and sensitive analog circuit blocks, which can be exacerbated by substrate coupling, and traditional conductive shields can adversely impact inductor performance.
Innovation Solution
A discontinuous guard ring is implemented around analog circuit blocks, featuring gaps in its metal and substrate components to minimize electromagnetic coupling with inductors, thereby reducing noise interference while maintaining optimal inductor performance and area efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a continuous guard ring is used to provide noise isolation, then noise isolation performance is improved, but inductor performance deteriorates due to electromagnetic coupling
Solution Approach 1:
The guard ring is divided into discrete segments rather than forming a continuous loop. Multiple gaps are introduced at different positions around the analog circuit block, breaking the continuous conductive path into separate sections. This segmentation reduces the electromagnetic coupling area between the guard ring and the inductor while preserving the noise isolation function of each individual segment.
2Productivity
If device density is increased to minimize costs, then manufacturing cost is reduced, but noise interference increases due to closer proximity of digital and analog blocks
Solution Approach 1:
The guard ring structure provides localized noise protection specifically around the analog circuit block without requiring global separation of digital and analog sections. The segmented guard ring creates local electromagnetic shielding zones that protect sensitive analog circuits from nearby digital noise sources, enabling high-density integration while maintaining signal integrity in critical areas.
3Object-affected harmful factors
If a conductive shield is positioned between analog and digital blocks to provide noise isolation, then noise isolation is improved, but chip area increases
Solution Approach 1:
The guard ring structure merges the noise isolation function with the existing substrate layout by positioning segments around the analog circuit block without requiring separate dedicated shield structures. The segmented design allows the guard ring to share space with other circuit elements and充分利用 available chip real estate, achieving effective noise isolation without proportionally increasing total chip area.
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 discontinuous guard ring effectively isolates noise from analog circuit blocks, preserving inductor performance and reducing electromagnetic disruption, while allowing for closer placement of digital and analog blocks, thus enhancing chip density and noise isolation without significant inductor performance degradation.
Implementation Method 1
a ring-shaped region disposed in the semiconductor substrate, having a dopant concentration level, and electrically coupled to the metal ring, to block noise in the semiconductor substrate from reaching the circuit block
Implementation Method 2
The discontinuous nature of the guard ring reduces or minimizes electromagnetic disruption of the performance of an inductor of the circuit block
Data Source
AI summary
An electronic apparatus includes a semiconductor substrate, a circuit block disposed in and supported by the semiconductor substrate and comprising an inductor, and a discontinuous noise isolation guard ring surrounding the circuit block. The discontinuous noise isolation guard ring includes a metal ring supported by the semiconductor substrate and a ring-shaped region disposed in the semiconductor substrate, having a dopant concentration level, and electrically coupled to the metal ring, to inhibit noise in the semiconductor substrate from reaching the circuit. The metal ring has a first gap and the ring-shaped region has a second gap.