Bidirectional SCR Structure for Faster ESD Recovery
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Solution Overview
Problem
Existing silicon-controlled rectifiers (SCRs) in integrated circuits face challenges in effectively managing electrostatic discharge (ESD) events, as they may remain in a low-impedance state longer than necessary, leading to potential damage from prolonged current conduction.
Innovation Solution
A structure for a silicon-controlled rectifier is designed with a semiconductor substrate featuring multiple doped regions and wells of different conductivity types, including a deep well and shallow trench isolation regions, which allows for a fully-isolated bidirectional device structure that efficiently directs ESD currents and enhances holding voltage and avalanche breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SCR remains in low-impedance state to conduct ESD current, then ESD protection is provided, but the SCR remains clamped longer than necessary causing prolonged current conduction that may damage sensitive devices
Solution Approach 1:
The patent segments the SCR structure into multiple regions with different doping concentrations and types (n-type regions, p-type regions, deep wells) to create distinct functional zones. This segmentation allows different parts of the SCR to perform specialized functions: some regions facilitate rapid triggering while others enable faster turn-off, resolving the contradiction between maintaining protection and limiting duration.
Solution Approach 2:
The patent applies local quality by creating regions with varying doping concentrations and types within the SCR structure. Specific local regions have optimized properties for triggering (lower holding voltage) while other local regions are optimized for rapid turn-off (higher holding current threshold), allowing the SCR to provide effective protection while limiting the duration of the low-impedance state.
2Speed
If the holding voltage is increased to ensure rapid return to high-impedance state, then the SCR returns faster post-ESD, but the voltage breakdown may be reduced affecting protection capability
Solution Approach 1:
The patent segments the voltage handling function across different regions: trigger regions are designed for lower breakdown voltages to initiate conduction, while holding regions are designed with higher breakdown characteristics to ensure rapid return to high-impedance state. This segmentation allows the SCR to achieve fast recovery without compromising overall protection capability.
Solution Approach 2:
The patent applies local quality by creating regions with optimized doping concentrations specifically tailored for rapid turn-off. These local regions have higher holding voltage characteristics that enable fast return to high-impedance state, while other regions maintain appropriate breakdown characteristics for effective ESD protection, resolving the contradiction between speed and strength.
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 proposed structure effectively manages ESD events by providing a bi-directional current path and increasing the holding voltage, reducing the risk of damage to integrated circuits while optimizing the SCR's operation during ESD events.
Implementation Method 1
a first terminal including a first doped region in the first well, and a second terminal including a second doped region in the second well. The first well, the second well and the first doped region have a first conductivity type, and the second doped region has a second conductivity type opposite to the first conductivity type
Implementation Method 2
An ESD event refers to an unpredictable electrical discharge of a positive or negative current over a short duration and during which a large amount of current is directed toward the integrated circuit
Data Source
AI summary
Structures for a silicon-controlled rectifier and methods of forming a structure for a silicon-controlled rectifier. The structure comprises a first well and a second well in a semiconductor substrate, a first terminal including a first doped region in the first well, and a second terminal including a second doped region in the second well. The first well, the second well and the first doped region have a first conductivity type, and the second doped region has a second conductivity type opposite to the first conductivity type. The structure further comprises a deep well in the semiconductor substrate. The deep well has the second conductivity type, the first well is positioned in a vertical direction between the deep well and the top surface of the semiconductor substrate, and the second well is positioned in the vertical direction between the deep well and the top surface of the semiconductor substrate.