SiC Trench MOSFET Body Doping for Threshold Voltage Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In silicon carbide (SiC) semiconductor elements with trench structures, differences in channel layer thickness and gate insulating film thickness on opposing side surfaces lead to varying threshold voltages, increasing ON-state resistance and deteriorating swing characteristics.
Innovation Solution
A silicon carbide semiconductor element with a body concentration adjusting region of varying dopant concentration on opposing side surfaces, controlled to equalize threshold voltages, is produced by implanting ions of specific conductivity types to match channel layer and gate insulating film thicknesses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If epitaxial growth is carried out on SiC substrate with trenches, then channel layer is formed on trench sidewalls, but the epitaxial film has different thicknesses on opposing side surfaces leading to varying threshold voltages
Solution Approach 1:
The patent applies local quality by creating a body region with different dopant concentrations at different locations. Specifically, the concentration of dopant of the second conductivity type is made higher in portions of the body region located beside first side surfaces of the gate trench compared to portions beside second side surfaces. This local variation in dopant concentration compensates for the non-uniform epitaxial film thickness, ensuring uniform threshold voltage across all trench sidewalls.
Solution Approach 2:
The patent changes the dopant concentration parameter in the body region to compensate for epitaxial thickness variations. By adjusting the dopant concentration of the second conductivity type in specific portions of the body region, the threshold voltage is equalized across opposing side surfaces despite differences in channel layer and gate insulating film thicknesses.
2Manufacturing precision
If dopant concentration is increased in body region portions beside first side surfaces, then threshold voltage is equalized across opposing side surfaces, but device structure becomes more complex
Solution Approach 1:
The patent implements local quality by creating spatially varying dopant concentration in the body region. The dopant concentration of the second conductivity type is higher in portions beside first side surfaces and lower in portions beside second side surfaces of the gate trench. This localized dopant distribution equalizes threshold voltages while maintaining a manageable structural complexity through targeted doping rather than overall structural redesign.
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 approach minimizes ON-state resistance and maintains consistent swing characteristics by ensuring equal threshold voltages on opposing side surfaces, enhancing the electrical performance of SiC semiconductor elements.
Implementation Method 1
the concentration of dopant of the second conductivity type in a body region which contacts with a channel layer to be grown on two opposing side surfaces of a gate trench are changed
Data Source
Figure 1(a)~1(b)
Figure 2~3
Figure 4(a)~4(c)
AI summary
This silicon carbide semiconductor element includes: a body region of a second conductivity type which is located on a drift layer of a first conductivity type; an impurity region of the first conductivity type which is located on the body region; a trench which runs through the body region and the impurity region to reach the drift layer; a gate insulating film which is arranged on surfaces of the trench; and a gate electrode which is arranged on the gate insulating film. The surfaces of the trench include a first side surface and a second side surface which is opposed to the first side surface. The concentration of a dopant of the second conductivity type is higher at least locally in a portion of the body region which is located beside the first side surface than in another portion of the body region which is located beside the second side surface.