SiC Trench Gate Epitaxial Growth and Hydrogen Etching
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Solution Overview
Problem
Existing silicon carbide (SiC) semiconductor devices with trench gate structures face challenges in achieving high withstand voltage and switching speed due to issues with gate insulation film breakdown and complex manufacturing processes, particularly related to ion-implantation methods that can cause defects and increase costs.
Innovation Solution
A method involving epitaxial growth to form a second conductivity type silicon carbide layer with rounded bottom and end layers within the trench, followed by hydrogen etching to remove the layer from side surfaces, eliminating the need for diagonal ion-implantation and simplifying the production process while reducing drain leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If diagonal ion-implantation is performed to form low concentration p type layer at both ends of trench, then switching characteristics are improved, but manufacturing process becomes complex and costs increase
Solution Approach 1:
The patent extracts and eliminates the complex diagonal ion-implantation process from the manufacturing flow. Instead of performing separate ion-implantation steps at both ends of the trench, the invention uses a simplified approach where the gate insulation film formation process itself addresses the electrical characteristics at the trench ends, removing the need for additional specialized processing steps while maintaining switching performance.
Solution Approach 2:
The patent changes the approach from modifying material composition through ion-implantation to controlling the gate insulation film parameters (thickness, formation conditions) during the standard manufacturing process. By adjusting the gate insulation film formation parameters, the invention achieves the desired electrical characteristics without introducing complex ion-implantation steps, thus simplifying the overall manufacturing process.
2Stress or pressure
If gate insulation film is formed in trench with high electric field intensity, then device can operate at high voltage, but gate insulation film is easily broken at corner portions of trench
Solution Approach 1:
The patent applies the curvature principle by ensuring that the gate insulation film is formed with appropriate thickness and continuity at the corner portions and end surfaces of the trench. The gate insulation film formation process is designed to cover the curved or angled surfaces at the trench ends, eliminating sharp corners where electric field concentration would cause breakdown. This curved surface approach distributes the electric field more evenly, maintaining high voltage capability while preventing gate insulation film breakage.
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 enables the production of SiC semiconductor devices with high withstand voltage and switching speed without relying on ion-implantation, reducing manufacturing complexity and costs, and preventing damage to the gate insulation film.
Implementation Method 1
epitaxially growing is performed to form a second conductivity type silicon carbide layer in the trench
Implementation Method 2
hydrogen etching is performed to leave the silicon carbide layer only at the bottom portion and the end of the trench
Data Source
Figure 1~2
Figure 3
Figure 4(a)~4(d)
AI summary
In a method for producing an SiC semiconductor device, a p type layer (31) is formed in a trench (6) by epitaxially growing, and is then left only on a bottom portion and ends of the trench by hydrogen etching, thereby to form a p type SiC layer (7). That is, a portion of the p type layer (31) formed on a side surface of the trench (6) is removed. Thus, the p type SiC layer (7) can be formed without depending on diagonal ion implantation. Since it is not necessary to separately perform the diagonal ion implantation, it is less likely that a production process will be complicated due to transferring into an ion implantation apparatus, and thus manufacturing costs reduce. Since there is no damage due to a defect caused by the ion implantation, it is possible to reduce a drain leakage and to reliably restrict the p type SiC layer (7) from remaining on the side surface of the trench (6). Accordingly, it is possible to produce an SiC semiconductor device that can achieve both high withstand voltage and high switching speed.