SiC IGBT Spreading Region Design for Low On-Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional IGBT structures are unsuitable for wide band-gap materials like SiC due to low carrier mobility and carrier concentration in the injector region, and damaged regions below junction implants lead to increased on-resistance and reduced current flow.
Innovation Solution
Incorporating a spreading region that is substantially thicker than the junction implants, formed of highly doped N material, to bypass damaged regions and improve front-side injection capabilities, thereby reducing on-resistance and enhancing conductivity modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional IGBT structure is used with wide band-gap materials, then the device can be manufactured, but the carrier mobility and carrier concentration in the injector region are low, resulting in high on-resistance
Solution Approach 1:
The patent changes the doping concentration parameter in the spreading region to be higher than in conventional structures (e.g., 1E18 to 1E20 atoms/cm³), which increases carrier concentration and improves conductivity modulation, thereby reducing on-resistance while maintaining the wide band-gap material benefits
Solution Approach 2:
The patent introduces an additional dimensional element by creating a spreading region that extends laterally beyond the drift region boundaries. This lateral extension provides alternative current paths and increases the effective conducting area, reducing the overall on-resistance of the device
2Ease of operation
If junction implants are formed in the drift region, then current flow can be controlled, but damaged regions below the junction implants increase on-resistance and reduce current flow
Solution Approach 1:
The patent introduces a spreading region as an intermediary layer between the junction implants and the drift region. This spreading region with higher doping concentration acts as a buffer that mitigates the harmful effects of damaged regions below the junction implants, allowing current flow control while reducing the negative impact on resistance
Solution Approach 2:
The patent performs preliminary doping of the spreading region to high concentrations before forming the junction implants. This preliminary action prepares the structure to handle the damaged regions that will be created during subsequent implantation processes, pre-establishing low-resistance paths that bypass the damaged areas
3Reliability
If the injector region is highly doped to improve carrier concentration, then conductivity increases, but the damaged regions from ion implantation increase on-resistance
Solution Approach 1:
The patent segments the injector region into two distinct parts: a highly doped spreading region and a less doped drift region. This segmentation allows the spreading region to provide high conductivity where needed while the drift region maintains lower doping to minimize damaged regions, thus resolving the contradiction between conductivity and damage reduction
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 significantly reduces on-resistance and improves current flow in SiC IGBT devices by bypassing damaged regions and promoting front-side injection, while also balancing blocking voltage and on-resistance.
Implementation Method 1
improve front-side injection capabilities
Implementation Method 2
enhancing conductivity modulation
Data Source
Figure 1
Figure 2
Figure 3
AI summary
An IGBT device includes an IGBT stack, a collector contact, a gate contact, and an emitter contact. The IGBT stack includes an injector region, a drift region over the injector region, a spreading region over the drift region, and a pair of junction implants in the spreading region. The spreading region provides a first surface of the IGBT stack, which is opposite the drift region. The pair of junction implants is separated by a channel, and extends from the first surface of the IGBT stack along a lateral edge of the IGBT stack towards the drift region to a first depth, such that the thickness of the spreading region is at least one and a half times greater than the first depth.