ESD Protection Circuit With Drift Isolation Region
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Solution Overview
Problem
Traditional n-type lateral diffused metal oxide semiconductor (nLDMOS) devices suffer from strong snapback and base push-out phenomena, leading to non-uniform turn-on and degraded ESD performance.
Innovation Solution
The design includes a substrate with specific well structures and dopant configurations, such as a first and second device well, a drift isolation region, and a drain well, which helps in directing current flow vertically and reducing base push-out, thereby improving ESD performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional nLDMOS structure is used, then device simplicity is maintained, but strong snapback and base push out phenomena occur leading to non-uniform turn on and degraded ESD performance
Solution Approach 1:
The device is segmented into multiple functional wells: a first device well containing the transistor, a second device well within the first well for drift region formation, and a drain well under the second diffusion region. This segmentation allows independent optimization of different device regions to achieve uniform turn-on and reduced snapback effects while maintaining manageable complexity through modular well structures
Solution Approach 2:
Different regions of the device are given different dopant concentrations and well depths to optimize local performance. The drift isolation region has specific doping characteristics, the second device well has different properties than the first, and the drain well is positioned and doped specifically to control base push-out. This local quality differentiation enables improved ESD performance without requiring complete redesign of the entire device structure
2Reliability
If drift isolation region is added between gate and second diffusion region, then base push out is reduced, but device structure complexity increases
Solution Approach 1:
The drift isolation region acts as an intermediary structure between the gate and the second diffusion region. It mediates the electric field distribution and carrier flow, preventing the direct interaction that causes base push-out. This intermediary region provides a controlled transition zone that ensures uniform turn-on without requiring complex external control mechanisms
3Reliability
If drain well is positioned under second diffusion region, then snapback effect is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The drain well is formed in advance during the manufacturing process, positioned at the predetermined location under the second diffusion region. By preparing this well structure beforehand with appropriate dopant concentration and depth, the snapback effect is preemptively controlled. The preliminary formation of the drain well establishes the correct electric field distribution before final device assembly, reducing the need for post-manufacturing adjustments
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 results in improved and more uniform turn-on of the ESD device, enhancing its performance by reducing base push-out and snapback effects.
Implementation Method 1
drift isolation region, which helps in directing current flow vertically
Data Source
AI summary
A device which includes a substrate defined with a device region having an ESD protection circuit is disclosed. The ESD protection circuit has a transistor. The transistor includes a gate having first and second sides. A first diffusion region is disposed adjacent to the first side of the gate and a second diffusion region is disposed in the device region displaced away from the second side of the gate. The first and second diffusion regions include dopants of a first polarity type. A drift isolation region is disposed between the gate and the second diffusion region. A first device well encompasses the device region and a second device well is disposed within the first device well. A drain well having dopants of the first polarity type is disposed under the second diffusion region and within the first device well.