Shared N-Well SCR Layout for Bidirectional ESD Protection
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Solution Overview
Problem
Conventional integrated circuit designs require two electrostatic discharge (ESD) devices to protect against both positive and negative voltage biases, leading to increased surface area and potential leakage current or voltage issues during non-ESD operation.
Innovation Solution
A structure featuring a p-type deep well over a substrate, with an n-type well between a pair of p-type wells, and additional n-type wells, forming multiple P-N-P junctions and semiconductor-controlled rectifiers (SCRs) that can be triggered by both positive and negative voltage biases, allowing for bi-directional ESD protection without additional surface area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two separate ESD devices are provided to protect against positive and negative voltage biases, then ESD protection coverage is improved, but surface area consumption increases
Solution Approach 1:
The patent merges two separate ESD protection devices into a single integrated structure by sharing a common first n-type well between two P-N-P junctions. This consolidation maintains protection against both positive and negative voltage biases while reducing the total surface area required, directly resolving the contradiction between comprehensive ESD coverage and area efficiency
Solution Approach 2:
The first n-type well serves multiple functions by being shared between two different P-N-P junctions that protect against opposite polarity voltage biases. This multi-functional design allows a single structure to perform what previously required two separate devices, thereby reducing area while maintaining reliability
2Reliability
If two separate ESD devices are provided for bidirectional protection, then ESD protection capability is improved, but leakage current increases
Solution Approach 1:
By merging two ESD protection paths into a single shared structure with common n-type well, the patent reduces the total number of active components that could contribute to leakage current. The shared well configuration minimizes redundant leakage paths while maintaining bidirectional protection capability through the complementary P-N-P junctions
Solution Approach 2:
The patent eliminates redundant ESD device structures that would contribute to leakage current during non-ESD operation. By recovering and reusing the same n-type well for both protection paths, the design discards unnecessary components that would otherwise generate harmful leakage effects
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 configuration enables a single ESD-protective device to handle both positive and negative voltage biases efficiently, reducing surface area requirements and minimizing leakage current or voltage issues during non-ESD operation.
Implementation Method 1
a first set of alternatingly doped wells to define a first N-P-N junction over the substrate
Implementation Method 2
the first SCR including a first set of alternatingly doped wells to define a first N-P-N junction
Implementation Method 3
a first set of alternatingly doped wells to define a first N-P-N junction over the substrate
Data Source
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AI summary
The disclosure provides a structure including an n-type well over an n-type deep well and between a pair of p-type wells for electrostatic discharge (ESD) protection. The structure may include a p-type deep well over a substrate, a first n-type well over the p-type deep well, and a pair of p-type wells over the p-type deep well. The pair of p-type wells are each adjacent opposite horizontal ends of the n-type well. A pair of second n-type wells are over the p-type deep well and adjacent one of the pair of p-type wells. Each p-type well is horizontally between the first n-type well and one of the second n-type wells.