Silicon Controlled Rectifier Latch-Up Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon Controlled Rectifiers (SCRs) face challenges with latch-up due to low holding voltage, especially in products operating in the 3-5 V range, and are not suitable for high-ohmic substrate wafers, requiring additional engineering and potential ESD failures.
Innovation Solution
A silicon controlled rectifier design with a further contact region of the second conductivity type in the second region, increasing the holding voltage without raising the operating voltage during ESD events, and allowing for self-biased or externally biased operation to prevent latch-up, suitable for high-ohmic substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a short-base SCR is used, then the holding voltage is low (2-3V), but the device is prone to latch-up in 3-5V operating ranges
Solution Approach 1:
The SCR structure is segmented into multiple regions (first region with first conductivity type, second region with second conductivity type) with additional contact regions distributed throughout. This segmentation allows the holding voltage to be distributed and controlled across multiple junctions, preventing latch-up while maintaining adequate protection voltage levels.
Solution Approach 2:
Different regions of the SCR are doped with different conductivity types and different doping concentrations to create localized properties. The contact regions are strategically positioned to provide local control over voltage distribution, enabling the device to maintain high holding voltage without causing latch-up in the overall device structure.
2Reliability
If a long-base SCR is used, then the holding voltage is high (above operating voltage), but the operating voltage during ESD events is higher which may be harmful to the protected IC
Solution Approach 1:
The SCR is divided into multiple doped regions with different conductivity types arranged in a specific pattern. This segmentation allows the holding voltage to be elevated above the operating voltage to prevent latch-up, while the distributed contact regions ensure that the operating voltage during ESD events remains controlled and does not exceed safe levels for the protected IC.
Solution Approach 2:
The doping concentrations and conductivity types of different regions are carefully controlled to adjust the voltage characteristics. By changing the doping parameters in specific regions, the holding voltage is increased above the operating voltage while maintaining safe operating voltage levels during ESD events, resolving the contradiction between latch-up prevention and IC protection.
3Reliability
If a long-base SCR is used, then the holding voltage is high, but additional engineering and special software tools are required which increases complexity
Solution Approach 1:
The ESD protection function and latch-up prevention function are merged into a single SCR device structure. The multiple doped regions and contact regions are integrated into one compact device that simultaneously provides both functions, eliminating the need for separate engineering efforts and special software tools that would be required for long-base SCR designs.
Solution Approach 2:
The SCR device is designed with multi-functionality, serving both as an ESD protection device and as a latch-up prevention device. The specific arrangement of doped regions and contact regions enables the device to provide high holding voltage for latch-up prevention while maintaining compatibility with standard IC manufacturing processes, reducing overall system complexity.
4Reliability
If a long-base SCR is used, then the holding voltage is high, but the device can only be used on low-ohmic substrate wafers which limits applicability
Solution Approach 1:
The SCR structure uses locally optimized doping regions with different conductivity types and concentrations. This local quality control allows the device to achieve high holding voltage for latch-up prevention while being compatible with both low-ohmic and high-ohmic substrate wafers, significantly improving adaptability to different substrate types and IC manufacturing processes.
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 design effectively increases the holding voltage of the SCR, preventing latch-up and enabling its use in applications with high-ohmic substrates without additional contact regions, reducing operating voltage and turn-on time, and providing effective ESD protection.
Implementation Method 1
a first region having a first conductivity type located in a semiconductor substrate; a second region having a second conductivity type located adjacent the first region in the semiconductor substrate, whereby a junction is formed at a boundary between the first region and the second region
Data Source
Figure 1~2
Figure 3A~3B
Figure 4
AI summary
A silicon controlled rectifier, an electrostatic discharge (ESD) protection circuit including the silicon controlled rectifier and an integrated circuit including the silicon controlled rectifier or ESD protection circuit. The silicon controlled rectifier includes a first region having a first conductivity type and a second region having a second conductivity type located adjacent the first region in a semiconductor substrate. A junction is formed at a boundary between the first region and the second region. Contact regions of the first conductivity type and the second conductivity type located in each of the first region and the second region. A further contact region of the second conductivity type is located in the second region, in between the contact region of the first conductivity type and the junction. The further contact region and the contact region of the second conductivity type in the second region are connected together for biasing the second region.