SiC Semiconductor Guard Rings with Embedded Injection Layer
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Solution Overview
Problem
Guard rings in semiconductor devices with floating potential struggle to maintain voltage and are affected by disturbances, leading to electric field concentration issues, especially in wide band gap semiconductors like SiC, where precise formation of embedded injection layers is challenging due to short impurity diffusion length.
Innovation Solution
A semiconductor device design featuring a plurality of guard rings surrounded by an embedded impurity region of the same conductivity type, connected at their bottom portions to alleviate electric field concentration and improve breakdown voltage reliability without requiring high position accuracy for the embedded injection layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guard rings with floating potential are used to surround the active area, then the depletion layer can spread toward the outer side to alleviate electric field concentration at the bottom end portion of the active area, but the guard rings cannot maintain voltage and are affected by disturbances (fixed charge, adsorption charge, external electric field)
Solution Approach 1:
The patent applies equipotentiality by connecting all guard rings to a common potential through the embedded injection layer. This ensures that the guard rings maintain a uniform potential distribution, preventing voltage fluctuations and disturbances while still allowing the depletion layer to spread effectively for breakdown voltage enhancement.
Solution Approach 2:
The embedded injection layer serves as an intermediary structure that connects the guard rings to the semiconductor substrate. This intermediary enables the guard rings to maintain stable potential while facilitating the spreading of the depletion layer, thus resolving the contradiction between voltage holding capability and breakdown voltage performance.
2Reliability
If the interval of individual guard rings is narrowed to less than a few μm in wide band gap semiconductors like SiC, then the depletion layer stretch can be sufficient, but it becomes extremely difficult to accurately form the embedded injection layer
Solution Approach 1:
The patent applies parameter changes by adjusting the conductivity type and concentration of the embedded injection layer to match or exceed those of the guard rings. This parameter optimization allows the embedded injection layer to be formed with relaxed precision requirements while still achieving the desired electrical connection and depletion layer spreading effect in wide band gap semiconductors.
3Reliability
If the concentration of guard rings and base is relatively high to form effective PN junctions, then the change in concentration in the vicinity of the PN junction surface becomes steeper, but this causes strong electric field concentration that needs to be alleviated by high temperature anneal processing
Solution Approach 1:
The patent applies local quality by creating a non-uniform concentration distribution in the embedded injection layer. The concentration is designed to be higher near the guard rings and gradually decrease toward the substrate, which locally optimizes the electrical connection while gradually alleviating the electric field concentration without requiring high temperature anneal processing.
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 suppresses electric field concentration and enhances breakdown voltage and reliability by ensuring the guard rings have equal potential and are connected to the depletion layer, even in wide band gap semiconductors, while simplifying the formation process and reducing the need for precise alignment.
Implementation Method 1
the electric field concentration at the bottom end portion of the active area (corner portion of the injection layer when viewed in cross-section) is alleviated
Implementation Method 2
the depletion layer easily spreads toward the outer side of the active area
Implementation Method 3
the change in impurity concentration in the vicinity of the PN junction surface
Implementation Method 4
the impurity diffusion is normally promoted by anneal processing performed at high temperature for a long time
Implementation Method 5
the impurity diffusion is normally promoted by anneal processing performed at high temperature for a long time
Implementation Method 6
anneal processing performed at high temperature for a long time to make the change in concentration in the vicinity of the PN junction surface gradual
Data Source
AI summary
A semiconductor device having high breakdown voltage and high reliability without forming an embedded injection layer with high position accuracy. The semiconductor device includes a base as an active area of a second conductivity type formed on a surface layer of a semiconductor layer of a first conductivity type to constitute a semiconductor element; guard rings as a plurality of first impurity regions of the second conductivity type formed on the surface layer of the semiconductor layer spaced apart from each other to respectively surround the base in plan view; and an embedded injection layer as a second impurity region of the second conductivity type embedded in the surface layer of the semiconductor layer to connect at least two bottom portions of the plurality of guard rings.