SiC Semiconductor Device Guard Ring Relocation
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Solution Overview
Problem
Silicon carbide (SiC) semiconductor devices face challenges in achieving high breakdown voltage while maintaining a simple structure, as existing techniques for Si MOSFETs are not optimal and can lead to electric field concentration and breakage due to the complexity of guard ring structures and impurity implantation processes.
Innovation Solution
A silicon carbide semiconductor device with a simplified structure featuring a guard ring region and a breakdown voltage holding layer, where the termination portion has only a single conductivity type, preventing pn junctions on the termination surface and shifting the element and termination surfaces in the thickness direction to avoid electric field concentration, and optionally covering the guard ring region to prevent electric field diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple embedded guard rings are provided at different depth positions in the n type base layer, then the maximum electric field of each stage is maintained to be equal to or less than the critical strength, but the structure of the semiconductor device becomes complicated and the manufacturing method becomes complicated due to increased number of times of performing impurity implantation step
Solution Approach 1:
The patent extracts the guard ring function from the element formation region and relocates it to the termination portion. By providing the guard ring region with a second conductivity type in the termination portion, the patent separates the termination function from the element formation function, thereby maintaining breakdown voltage without complicating the element formation region structure or requiring multiple impurity implantation steps in the base layer
Solution Approach 2:
The patent shifts the guard ring from the vertical depth positions within the base layer to the lateral termination portion surrounding the element portion. This dimensional relocation allows the guard ring to function at the termination surface rather than embedded within the active region, simplifying both structure and manufacturing
2Reliability
If guard rings are provided at multiple depth positions in the n type base layer, then the maximum electric field of each stage is maintained to be equal to or less than the critical strength, but the manufacturing method becomes complicated due to increased number of times of performing impurity implantation step
Solution Approach 1:
The patent extracts the guard ring function from the element formation region and relocates it to the termination portion. By providing the guard ring region with a second conductivity type in the termination portion, the patent separates the termination function from the element formation function, thereby maintaining breakdown voltage without complicating the element formation region structure or requiring multiple impurity implantation steps in the base layer
Solution Approach 2:
The patent merges the guard ring formation with the termination portion structure. Instead of performing separate impurity implantation steps for embedded guard rings at multiple depth positions, the guard ring region is formed as an integrated part of the termination portion, reducing the number of manufacturing steps
3Device complexity
If a single guard ring is provided at the surface of the n type base layer, then the structure is simplified, but electric field concentration takes place in the vicinity of the surface of the semiconductor layer causing breakage
Solution Approach 1:
The patent applies different conductivity types to different regions: the element formation region maintains the first conductivity type (n type) while the termination portion has a guard ring region with the second conductivity type (p type). This local differentiation allows the termination portion to control electric field distribution without affecting the element formation region, preventing electric field concentration at the surface while maintaining structural simplicity
Solution Approach 2:
The guard ring region with the second conductivity type acts as an intermediary between the element formation region and the termination surface. It mediates the electric field distribution by creating a gradual transition zone that prevents abrupt field concentration at the surface, thereby maintaining both structural simplicity and high breakdown voltage
Data Source
AI summary
A silicon carbide film has first and second main surfaces. The second main surface has an element formation surface and a termination surface. The silicon carbide film has a first range that constitutes a first main surface and an intermediate surface opposite to the first main surface, and a second range that is provided on the intermediate surface and constitutes the element formation surface. The first range includes: a first breakdown voltage holding layer, and a guard ring region partially provided at the intermediate surface in the termination portion. The second range has a second breakdown voltage holding layer. The second range has one of a structure only having the second breakdown voltage holding layer in the termination portion and a structure disposed only in the element portion of the element portion and the termination portion.