ESD Protection Layout With Trigger Diodes to Prevent Latch-Up
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Solution Overview
Problem
Existing electro-static discharge (ESD) protection devices based on silicon controlled rectifiers (SCRs) or thyristors have high trigger voltages that can damage devices and low holding voltages, leading to latch-up phenomena, which degrade the reliability of electronic devices.
Innovation Solution
The ESD protection device incorporates a substrate with specific diffusion regions and wells of varying conductive types, along with trigger diodes electrically connected to lower the trigger voltage and increase the holding voltage, preventing latch-up by utilizing reverse breakdown in trigger diodes instead of between N and P wells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a typical ESD protection device based on SCR is used, then the device structure is simple, but the trigger voltage is high which can destroy transistors
Solution Approach 1:
The patent segments the trigger mechanism by introducing separate trigger diodes (first trigger diode and second trigger diode) that are electrically connected in series between the N well and P well. This segmentation allows the trigger function to be independent from the main SCR structure, enabling lower trigger voltage that does not destroy connected transistors while maintaining simple overall device structure.
Solution Approach 2:
The trigger diodes serve as intermediary elements between the N well and P well. Instead of directly relying on the high reverse breakdown voltage between N and P wells for triggering, the trigger diodes mediate the triggering process with their lower forward voltage drop, thus reducing the trigger voltage to a safe level for connected transistors.
2Ease of manufacture
If a typical ESD protection device based on SCR is used, then the manufacturing process is simple, but the holding voltage is low which causes latch-up phenomenon
Solution Approach 1:
The patent applies local quality by introducing specific diffusion regions (fifth, sixth, seventh, and eighth diffusion regions) with different conductive types at specific locations within the SCR structure. These localized doped regions modify the electrical characteristics in specific areas, increasing the holding voltage to prevent latch-up while maintaining the overall simplicity of the manufacturing process using standard semiconductor fabrication techniques.
3Strength
If the trigger voltage is high, then the ESD protection device can protect against high voltage, but it can destroy transistors that constitute electronic devices
Solution Approach 1:
The trigger diodes act as intermediaries that decouple the protection capability from the trigger voltage level. The SCR structure maintains its ability to handle high ESD voltages for protection, while the trigger diodes ensure that the actual triggering voltage remains low and safe for connected transistors, thus resolving the contradiction between protection strength and transistor safety.
Solution Approach 2:
By segmenting the voltage handling function - with trigger diodes handling the low-voltage triggering and the SCR structure handling the high-voltage protection - the patent achieves both high protection capability and low trigger voltage that prevents transistor damage.
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 effectively reduces the trigger voltage and prevents latch-up, enhancing the reliability of electronic devices by ensuring safe discharge of ESD current through the device.
Implementation Method 1
utilizing reverse breakdown in trigger diodes instead of between N and P wells
Data Source
AI summary
An electro-static discharge protection device includes a substrate that includes a first well that has a first conductive type and a second well that has a second conductive type, and first to eighth diffusion regions formed on the first well and the second well. At least a portion of the diffusion regions formed in the first well are connected to a first electrode, and at least a portion of diffusion regions formed in a second well are connected to a second electrode. The contact between one of diffusion regions formed in the first well and an N well forms a trigger diode. A junction between one of diffusion regions formed in a second well and a P well forms a trigger diode. The trigger diodes are electrically connected to each other.