Super-Junction Guard Ring Layout for Terminal Charge Balance
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Solution Overview
Problem
Super-junction devices face premature breakdown due to charge imbalance and edge electric-field concentration in the terminal region, leading to reduced voltage withstand reliability.
Innovation Solution
A guard ring with segmentally doped regions and undoped semiconductor pillars is introduced in the terminal region to improve impurity distribution and charge balance, ensuring a continuous semiconductor ring of a single dopant type that optimizes edge electric-field distribution and maintains charge balance between adjacent semiconductor pillars.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a guard ring is formed by continuously doping top-end portions of P-type and N-type semiconductor pillars in the terminal region, then edge electric-field distribution can be optimized, but charge balance between P-type and N-type pillars is destroyed leading to premature breakdown
Solution Approach 1:
The guard ring doping is divided into segments rather than continuous doping. Specifically, only every other pillar (either P-type or N-type) receives guard ring doping, creating a segmented pattern that maintains charge balance while still providing edge field optimization. This segmentation prevents the charge imbalance that would occur with continuous doping of all pillars.
Solution Approach 2:
Different regions of the terminal region are treated differently with respect to doping. The guard ring doping is applied locally to specific pillars rather than uniformly to all pillars. This local differentiation allows optimization of edge electric fields in critical areas while preserving charge balance in the overall structure by leaving other pillars undoped.
2Area of stationary object
If the area of the super-junction device is limited, then device size is reduced, but charge imbalance occurs in edge cells under reverse bias state leading to premature breakdown
Solution Approach 1:
The guard ring structure is formed in advance in the terminal region to preemptively address the charge imbalance issue that would occur in edge cells. By pre-configuring the doping pattern in the terminal region before the device operates, the structure is prepared to handle reverse bias conditions and prevent premature breakdown without requiring a larger device area.
Solution Approach 2:
The guard ring acts as an intermediary structure between the cell region and the terminal region edge. It mediates the electric field distribution at the boundary, providing a transition zone that prevents direct exposure of edge cells to harmful electric field concentrations, thus protecting the limited device area from premature breakdown.
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 solution enhances voltage withstand reliability by maintaining charge balance and optimizing electric-field distribution, preventing premature breakdown and ensuring normal operation of the super-junction device.
Implementation Method 1
PN junctions are each formed between a corresponding one of the P-type semiconductor pillars and a corresponding one of the N-type semiconductor pillars
Implementation Method 2
Due to transverse termination of charge electric line of force, the whole drift region is approximate to an intrinsic layer in a longitudinal direction of a withstand voltage, thus longitudinal electric field can be modulated
Implementation Method 3
a guard ring is formed in the terminal region, so that edge electric-field distribution of the cell region can be optimized and a normal withstand voltage of the cell region can be ensured
Data Source
AI summary
Disclosed is a super-junction device, comprising a semiconductor substrate and a super-junction structure on a first surface of the semiconductor substrate. The super-junction structure includes first semiconductor pillars and second semiconductor pillars. The super-junction device has a cell region and a terminal region surrounding the cell region, the super-junction structure has a portion located in the cell region, and another portion located in the terminal region. The super-junction device further includes a guard ring located in the terminal region and surrounding the cell region, the guard ring includes doped regions extending segmentally and top-end portions of a first set of semiconductor pillars connecting the doped regions into a continuous ring. The top-end portions of the first set of semiconductor pillars in the guard ring are undoped, thus improving impurity distribution of the guard ring, charge balance in the terminal region, and voltage withstand performance of the super-junction device.