SiC Semiconductor JTE Structure for High Breakdown Voltage
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Solution Overview
Problem
The challenge in silicon carbide semiconductor devices is to achieve a stable termination structure that provides high breakdown voltage, as existing junction termination extension (JTE) structures face limitations due to electric field concentration and impurity concentration gradients, making it difficult to reduce manufacturing costs and improve breakdown voltage performance.
Innovation Solution
A semiconductor device with a concentric JTE structure featuring alternating p-type regions of varying widths and impurity concentrations, including an intermediate region with a gradual impurity concentration gradient, to relax the electric field and enhance breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional JTE structure with p-type high-concentration region and p-type low-concentration region is used, then the electric field is relaxed on the outer peripheral portion of the p-type high-concentration region, but the breakdown voltage is limited by avalanche breakdown in the outer peripheral portion of the p-type low-concentration region
Solution Approach 1:
The termination structure is divided into multiple concentric regions with different impurity concentrations: a first p-type region with first impurity concentration, a second p-type region with second impurity concentration lower than the first, and a third p-type region with third impurity concentration lower than the second. This segmentation distributes the electric field relaxation function across multiple zones, preventing avalanche breakdown in a single low-concentration region while maintaining high breakdown voltage.
Solution Approach 2:
Each concentric region is assigned a specific impurity concentration tailored to its location and function. The first p-type region near the active region has higher impurity concentration for strong field control, while outer regions have progressively lower concentrations for gradual field relaxation. This local optimization of impurity concentration profiles resolves the contradiction between field relaxation and breakdown voltage limitation.
2Reliability
If multiple p-type low-concentration regions with different impurity concentrations or thicknesses are formed adjacently to create a JTE structure, then the breakdown voltage performance is improved, but the number of processes increases leading to higher manufacturing costs
Solution Approach 1:
Multiple p-type regions with different impurity concentrations are merged into a single integrated termination structure with concentric arrangement. Instead of forming separate structures through multiple independent processes, the invention combines all p-type regions into one unified structure that can be formed through coordinated ion implantation and thermal diffusion steps, reducing process complexity and manufacturing cost.
Solution Approach 2:
The impurity concentration parameter is systematically varied across the concentric regions to achieve the desired electric field profile. By controlling the impurity concentration gradient from inner to outer regions, the structure achieves optimal breakdown voltage performance while simplifying the manufacturing process through parameter optimization rather than structural complexity.
3Manufacturing precision
If ion implantation with high acceleration voltage is used to introduce impurities in silicon carbide semiconductor devices, then the impurity introduction is effective, but the thermal diffusion of impurities is extremely small making it difficult to apply VLD structure
Solution Approach 1:
Ion implantation with high acceleration voltage is performed first to precisely introduce impurities at desired locations and concentrations. Subsequently, thermal diffusion is applied to enable controlled impurity redistribution. This preliminary ion implantation followed by thermal diffusion allows the formation of gradual impurity concentration gradients in the concentric regions, overcoming the limitation of extremely small thermal diffusion in silicon carbide.
Solution Approach 2:
Thermal diffusion acts as an intermediary process between high-energy ion implantation and the final impurity concentration distribution. The thermal diffusion step mediates the transition from discrete ion implantation zones to smooth, gradual impurity concentration gradients across the concentric p-type regions, enabling the VLD-like structure despite silicon carbide's low thermal diffusion characteristics.
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 proposed structure effectively relaxes the electric field and increases the breakdown voltage by distributing electric field concentration points, improving the critical field strength and reducing manufacturing costs through a more gradual impurity concentration gradient.
Implementation Method 1
the intermediate region of the second conductivity type... having an impurity concentration lower than the semiconductor region of the second conductivity type, adjacent on an inner side and an impurity concentration higher than the semiconductor region of the second conductivity type, adjacent on an outer side... effectively relaxes the electric field and increases the breakdown voltage by distributing electric field concentration points
Implementation Method 2
a depletion layer extends from a pn junction between the p-type high-concentration region and the n−-type drift layer to the outside (toward a chip outer peripheral portion) and spreads to both the p-type high-concentration region and the p−-type low-concentration region
Data Source
AI summary
A semiconductor device, including a substrate of a first conductivity type, an active region and a termination structure portion formed on a front surface of the substrate, and a plurality of regions of a second conductivity type formed concentrically surrounding the periphery of the active region in the termination structure portion. Each region has a higher impurity concentration than one of the regions adjacent thereto on an outside thereof. The plurality regions include first and second semiconductor regions, and an intermediate region sandwiched between, and in contact with, the first and second semiconductor regions, and a third semiconductor region. The intermediate region includes a plurality of first subregions and a plurality of second subregions that are alternately arranged along a path in parallel to a boundary between the active region and the termination structure portion, the second subregions having a lower impurity concentration than the first subregions.