SiC FET Edge Termination Doping for Voltage Blocking
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Solution Overview
Problem
Field effect transistors (FETs) face challenges in optimizing electric switching losses and voltage blocking capability, particularly in silicon carbide (SiC) semiconductor devices, where reducing device geometry to improve functionality per unit area leads to trade-offs that are difficult to manage.
Innovation Solution
The FET design includes a silicon carbide semiconductor body with a transistor cell area and an edge termination area, where the net doping concentration in the drift region is higher in the transistor cell area than in the edge termination area, allowing for reduced doping in the edge termination area through ion implantation of light ions to enhance voltage blocking capability and reduce avalanche multiplication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If device geometry is shrunk to improve functionality per unit area, then productivity increases, but voltage blocking capability deteriorates
Solution Approach 1:
The patent applies different net doping concentrations to different regions of the drift region: higher doping in the transistor cell area for optimal switching performance, and lower doping in the edge termination area for enhanced voltage blocking capability. This local differentiation resolves the contradiction by allowing each region to be optimized for its specific function rather than using a uniform design.
Solution Approach 2:
The drift region is segmented into two distinct areas with different doping characteristics: the transistor cell area and the edge termination area. This segmentation allows independent optimization of each region - the transistor cell area for switching losses and the edge termination area for voltage blocking - thereby resolving the trade-off between productivity and reliability.
2Reliability
If doping concentration is increased to improve voltage blocking capability, then reliability improves, but electric switching losses increase
Solution Approach 1:
The patent implements local quality by assigning different net doping concentrations to different functional areas: the transistor cell area uses higher doping concentration to minimize switching losses, while the edge termination area uses lower doping concentration to maximize voltage blocking capability. This spatial differentiation eliminates the need to choose between the two conflicting requirements.
3Ease of manufacture
If uniform doping is used to simplify manufacturing, then ease of manufacture improves, but device performance deteriorates
Solution Approach 1:
The patent employs local quality by creating a non-uniform doping profile with distinct net doping concentrations in the transistor cell area versus the edge termination area. This approach prioritizes device performance over manufacturing simplicity, as the differentiated doping enables both regions to achieve their optimal performance 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
This design increases voltage blocking capability, reduces avalanche multiplication, and minimizes chip area consumption while maintaining reliable electric characteristics by optimizing the doping concentration profile across the device.
Implementation Method 1
a net doping concentration in the drift region may be larger in the transistor cell area than in the edge termination area
Implementation Method 2
reducing doping in the edge termination area through ion implantation of light ions
Data Source
AI summary
A field effect transistor (FET) is proposed. The FET includes a transistor cell area in a silicon carbide (SiC) semiconductor body. An edge termination area surrounds the transistor cell area. A source contact is arranged over a first surface of the SiC semiconductor body. A drain contact is arranged on a second surface of the SiC semiconductor body. The FET further includes a drift region of a first conductivity type between the first surface and the second surface. Along a lateral direction, a net doping concentration in the drift region is larger in the transistor cell area than in the edge termination area.