Bi-directional SCR ESD Protection Circuit with Double Emitters
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Solution Overview
Problem
Current ESD protection circuits in integrated circuits fail to provide a sufficiently high holding voltage, leading to inadequate latchup immunity and potential damage from electrostatic discharge events.
Innovation Solution
Incorporating a bi-directional Silicon Controlled Rectifier (SCR) with double emitter regions, which increases the holding voltage by modulating the current flow and voltage across the ESD protection device, allowing for improved latchup immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bi-directional SCR with single emitter region is used, then the device can conduct large currents during ESD events, but the holding voltage is insufficient leading to poor latchup immunity
Solution Approach 1:
The SCR emitter region is segmented into multiple emitter regions (first emitter region and second emitter region) instead of using a single emitter region. This segmentation allows the SCR to achieve higher holding voltage and improved latchup immunity while maintaining the ability to conduct large currents during ESD events.
Solution Approach 2:
Different regions of the SCR are given different doping concentrations and structures. The first emitter region has a first doping concentration while the second emitter region has a second doping concentration, creating local quality variations that optimize both holding voltage and current conduction capabilities.
2Reliability
If the holding voltage is increased to improve latchup immunity, then protection robustness improves, but the device structure becomes more complex
Solution Approach 1:
Multiple emitter regions are merged within a single SCR structure rather than using separate protection devices. This merging approach achieves higher holding voltage and improved protection robustness while avoiding the need for additional discrete components or circuits.
Solution Approach 2:
The SCR with multiple emitter regions serves multiple functions: it provides ESD protection, achieves high holding voltage for latchup immunity, and maintains low on-state voltage drop. This multi-functionality is achieved within a single device structure rather than requiring multiple separate components.
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 enhanced holding voltage ensures robust protection against latchup, preventing damage from electrostatic discharge events by conducting higher currents safely within the integrated circuit.
Implementation Method 1
Electrostatic discharge (ESD) is a problem in the utilization, manufacturing and/or design of the semiconductor devices
Implementation Method 2
One type of ESD circuit used today includes a bi-directional Silicon Controlled Rectifier (SCR) coupled with a PNP transistor
Data Source
AI summary
An electrostatic discharge (ESD) protection device includes a first bi-directional silicon controlled rectifier having a doped well of a first conductivity type, a buried doped layer having a second conductivity type opposite the first conductivity type, first and second highly doped regions of the second conductivity type in the doped well, and a third highly doped region of the first conductivity type in the doped well. The first, second and third highly doped regions are connected to a first node. A first transistor in the doped well includes an emitter coupled to the first highly doped region, a collector coupled to a conductive line in the buried doped layer, and a base coupled to the third highly doped region. A second transistor in the doped well includes an emitter coupled to the second highly doped region, a collector coupled to the conductive line in the buried doped layer, and a base coupled to the third highly doped region.