ESD Bus Segmentation for EMI Noise Isolation in ICs
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Solution Overview
Problem
Traditional ESD protection schemes in integrated circuits often compromise on electromagnetic interference (EMI) noise isolation, leading to increased EMI propagation in higher frequency and smaller dimension integrated circuits, which affects the performance and reliability of devices.
Innovation Solution
An ESD protection scheme is implemented where the ESD bus is electrically isolated from substrate well regions and coupled to an external ground, using a separate conductive layer, and bidirectional ESD protection elements like back-to-back diode pairs or active MOSFET clamping devices to reduce noise propagation between circuit domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional ESD protection schemes are used with substrate well regions, then ESD protection is provided, but EMI noise propagation increases
Solution Approach 1:
The ESD bus is segmented into separate conductive layers (first ESD bus in third conductive layer, second ESD bus in fourth conductive layer) that are electrically isolated from substrate well regions. This segmentation allows ESD protection functionality to be maintained while physically separating the ESD current path from sensitive substrate regions, thereby preventing EMI noise propagation to functional circuits.
Solution Approach 2:
The ESD bus is extracted from the substrate well regions and implemented as a separate conductive structure. By taking out the ESD protection path from the substrate and creating an independent ESD bus that does not share electrical connection with substrate well regions, the harmful EMI noise is isolated from the main substrate, resolving the contradiction between ESD protection and EMI isolation.
2Reliability
If ESD bus is electrically coupled to substrate well regions, then ESD current can be discharged, but noise isolation between circuit domains deteriorates
Solution Approach 1:
The ESD protection system is segmented into multiple independent conductive layers. The first ESD bus in the third conductive layer and second ESD bus in the fourth conductive layer are electrically isolated from substrate well regions, creating separate discharge paths that prevent noise coupling while maintaining ESD discharge capability through alternative routes.
Solution Approach 2:
The ESD bus is moved to higher conductive layers (third and fourth conductive layers) above the substrate, creating a three-dimensional separation. This dimensional change allows ESD current to be discharged through vertical paths in upper layers without horizontal coupling to substrate well regions, thereby maintaining discharge capability while improving noise isolation.
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 effectively minimizes EMI noise propagation, enhancing the performance and reliability of integrated circuits by isolating noise from sensitive and aggressor circuits, and allowing for improved noise isolation between power/ground domains.
Implementation Method 1
bidirectional ESD protection elements like back-to-back diode pairs
Implementation Method 2
active MOSFET clamping devices
Implementation Method 3
the ESD bus is not tied to the substrate well regions associated with EMI aggressor and sensitive circuits of the IC, but instead is a separate conductive layer
Data Source
AI summary
An electrostatic discharge (ESD) protection scheme is provided that reduces EMI noise propagation among functional circuit blocks of an integrated circuit (IC). Traditional ESD protection schemes include an ESD bus electrically tied to the substrate of an integrated circuit (e.g., a P-well) and substrate well regions associated with electromagnetic interference (EMI) aggressor and sensitive circuits. These electrical couplings can propagate EMI noise on the ESD bus throughout the circuit blocks of the IC. Embodiments provide an ESD bus that is not tied to the substrate well regions associated with EMI aggressor and sensitive circuits of the IC, but instead is a separate conductive layer electrically coupled to an external ground. In this manner, the device circuits are isolated from EMI noise carried in the ESD bus, thereby protecting the various functional blocks from such noise.