SiC Semiconductor Termination Structure for Electric Field Relaxation
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Solution Overview
Problem
Existing semiconductor devices with silicon carbide (SiC) materials face challenges in reducing surface electric field concentrations and variability in breakdown voltage due to pn junctions and impurity concentration control issues, leading to high surface electric fields and manufacturing variations.
Innovation Solution
A semiconductor device design featuring a surface outer circumferential structure with layered impurity concentrations, including a high-concentration layer, electric field relaxing layers, and a channel stop layer, which reduces electric field concentrations and variability in breakdown voltage by forming a High-Low junction and embedding a p+ region in a p− layer, allowing for breakdown voltage formation without modifying the n drift layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pn junction termination structure is used in the outer circumference of a semiconductor element, then breakdown voltage can be achieved, but surface electric field concentration occurs leading to high variability in breakdown voltage
Solution Approach 1:
The patent changes the impurity concentration parameter by introducing a graded concentration profile in the termination structure, transitioning from a abrupt pn junction to a structure with continuously varying impurity concentration. This parameter change reduces electric field concentration and achieves more consistent breakdown voltage characteristics across manufactured devices.
Solution Approach 2:
The patent applies local quality by creating different impurity concentration regions at specific locations in the termination structure. The impurity concentration is locally adjusted to be higher near the junction and gradually decrease toward the surface, optimizing the electric field distribution locally to prevent surface flashover while maintaining bulk breakdown voltage.
2Object-affected harmful factors
If impurity concentration is spatially modulated with gradual decrease, then electric field relaxation is achieved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the termination structure into distinct regions with different impurity concentration characteristics: a high-concentration region near the junction, a graded concentration region in the middle, and a low-concentration region at the surface. This segmentation allows the complex impurity profile to be achieved through controlled manufacturing processes while maintaining the beneficial electric field relaxation effect.
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 effectively relaxes electric fields at the surface, reduces breakdown voltage variation, and simplifies the manufacturing process by forming a termination structure with high yield and improved reliability.
Implementation Method 1
a first electric field relaxing layer continuous to the high-concentration layer at an outer circumference of the high-concentration layer, the first electric field relaxing layer having a second impurity concentration lower than the first impurity concentration; a second electric field relaxing layer continuous to the first electric field relaxing layer at an outer circumference of the first electric field relaxing layer, the second electric field relaxing layer having a third impurity concentration lower than the second impurity concentration
Implementation Method 2
a channel stop layer located at an ultimate end of the surface outer circumferential portion, the channel stop layer being connected to the first electric field diffusion layer, the channel stop layer having an impurity concentration higher than an impurity concentration of the first conductivity type thin film
Data Source
AI summary
The second conductivity type thin film includes: a high-concentration layer having a first impurity concentration; a first electric field relaxing layer continuous to the high-concentration layer at an outer circumference of the high-concentration layer, the first electric field relaxing layer having a second impurity concentration lower than the first impurity concentration; a second electric field relaxing layer continuous to the first electric field relaxing layer at an outer circumference of the first electric field relaxing layer, the second electric field relaxing layer having a third impurity concentration lower than the second impurity concentration; and a first electric field diffusion layer continuous to the second electric field relaxing layer at an outer circumference of the second electric field relaxing layer, the first electric field diffusion layer having a fourth impurity concentration lower than the third impurity concentration.