SiC Trench Gate MOSFET Current Diffusion Region
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Solution Overview
Problem
Silicon carbide trench gate MOSFET devices face challenges with high electric fields causing premature breakdown of the gate dielectric and limited short circuit capability due to small on-resistance, leading to serious heating and reduced short circuit performance compared to plane gate MOSFETs.
Innovation Solution
Incorporating an injection-type current diffusion region with a concave shape and higher doping concentration around the bottom of the trench gate, along with epitaxial protection regions and a shielding region, to reduce electric fields and enhance short circuit capability, while maintaining high breakdown voltage and on-state resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional trench gate structure is used, then the on-state resistance is reduced due to elimination of JFET region and higher channel density, but the gate dielectric breakdown voltage is reduced due to high electric field concentration at trench corners
Solution Approach 1:
The patent applies local quality by introducing a concave-shaped injection-type current diffusion region specifically at the bottom of the trench gate where the electric field is most concentrated. This localized structural modification targets the critical area of high electric field stress without altering the overall trench gate structure, thereby protecting the gate dielectric at the most vulnerable location while preserving the low on-state resistance characteristics of the trench gate MOSFET.
Solution Approach 2:
The patent introduces a vertical dimension by creating a concave-shaped injection-type current diffusion region that extends downward from the trench bottom. This dimensional change allows the current diffusion region to wrap around the trench gate bottom, effectively increasing the distance between the high electric field region and the gate dielectric, thereby reducing electric field concentration without compromising the horizontal channel structure.
2Productivity
If the on-resistance is reduced to improve switching performance, then the short circuit current increases causing serious heating and reduced short circuit capability
Solution Approach 1:
The patent converts the harmful effect of high short circuit current into a beneficial effect by utilizing the concave-shaped injection-type current diffusion region to deliberately increase the on-resistance. The higher doping concentration in this region creates a controlled resistance increase that limits short circuit current, transforming the previously harmful high current condition into a protected state with reduced heating and improved short circuit capability.
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 reduces heating during short circuits, improves short circuit capability, and maintains high breakdown voltage by separating the electric field peak from the current peak, with optimized device characteristics achieved through the use of a thinner epitaxial layer.
Implementation Method 1
a high electric field in an SiC drift region causes an extremely high electric field on a gate dielectric, and this problem is aggravated at trench corners
Implementation Method 2
a doping concentration of the injection-type current diffusion region is higher than a doping concentration of the epitaxial layer and a doping concentration of the epitaxial well region
Implementation Method 3
due to the relatively small on-resistance of a trench MOSFET, circuit current is relatively large when a short circuit occurs, the device heats up seriously
Data Source
AI summary
The present disclosure provides a silicon carbide trench gate metal oxide semiconductor field effect transistor (MOSFET) and a method for manufacturing thereof. The silicon carbide trench gate MOSFET includes: a substrate having a first doping type, an epitaxial layer formed on the substrate and having the first doping type, an epitaxial well region formed above the epitaxial layer and having a second doping type, a first source contact region formed in the epitaxial well region and having the first doping type, a second source contact region formed in the epitaxial well region and having the second doping type, a trench gate, a source electrode and a drain electrode, wherein the trench gate includes a gate dielectric and a gate electrode, the silicon carbide trench gate MOSFET further includes a injection-type current diffusion region, which is wrapped around the bottom of the trench gate and has the first doping type.