SiC Trench Structure with Angled Connections

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Solution Overview

Problem

Silicon carbide semiconductor devices with straight trench structures face issues of electric field localization at trench end portions, leading to potential breakdown due to defects caused by dry etching and heat treatment, which narrows or deforms the trench connections, especially with varying curvature and cell pitch.

Innovation Solution

The method involves connecting the end portions of adjacent straight trenches to form polygons using angled trench sections, such as 30 degrees or 60 degrees, to prevent deformation and filling during heat treatment, ensuring stable trench structures and preventing electric field localization.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If straight trenches are formed in the silicon carbide semiconductor device, then the manufacturing process is simple and efficient, but electric field localization occurs at the trench end portions leading to device breakdown

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoiddevice breakdown resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent applies curvature by rounding the end portions of straight trenches to eliminate sharp corners. This curvature modification prevents electric field localization at the trench ends, thereby avoiding device breakdown while maintaining the overall straight trench structure for manufacturing efficiency.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent introduces asymmetry by connecting adjacent straight trenches with angled sections (30 degrees or 60 degrees) instead of using symmetric rounded ends. This asymmetric connection pattern prevents electric field localization while maintaining manufacturing simplicity.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If the trench end portions are rounded or connected to remove pointing ends, then electric field localization is reduced, but the trench structure becomes more complex and difficult to manufacture

Engineering Contradiction:

Improveelectric field distributionVSAvoidtrench formation complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent uses controlled rounding of trench end portions with specific radius values (0.5-2.0 μm) that can be achieved through standard photolithography and etching processes. This maintains ease of manufacture while effectively reducing electric field localization.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The patent employs asymmetric angled connections (30 or 60 degrees) between straight trenches, which can be implemented using conventional photomask patterns and etching processes, thus maintaining manufacturing simplicity while improving electric field distribution.

Inventive Principle:

Principle #4Asymmetry

3Manufacturing precision

If heat treatment is applied to the silicon carbide semiconductor device, then the trench shape is improved and impurity atoms are activated, but the trench connections narrow or deform especially with varying curvature and cell pitch

Engineering Contradiction:

Improvetrench shape qualityVSAvoidtrench connection integrity

Core Design Contradiction:

Manufacturing precisionVSStability of the object's composition

Solution Approach 1:

The patent uses asymmetric angled connections (30 or 60 degrees) that are more resistant to heat-induced deformation compared to curved connections. This asymmetric geometry maintains trench connection integrity during heat treatment while still preventing electric field localization.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent optimizes the angles (30 or 60 degrees) and dimensions of the connecting sections to withstand heat treatment temperatures. These parameter selections prevent narrowing or deformation of trench connections during heat treatment while maintaining the benefits of reduced electric field localization.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS8648353B2Method for manufacturing silicon carbide semiconductor device and the silicon carbide semiconductor device

Publication Date: 2014.02.11 FUJI ELECTRIC SYST CO LTD

AI summary

Silicon carbide semiconductor device includes trench, in which connecting trench section is connected to straight trench section. Straight trench section includes first straight trench and second straight trench extending in parallel to each other. Connecting trench section includes first connecting trench perpendicular to straight trench section, second connecting trench that connects first straight trench and first connecting trench to each other, and third connecting trench that connects second straight trench and first connecting trench to each other. Second connecting trench extends at 30 degrees of angle with the extension of first straight trench. Third connecting trench extends at 30 degrees of angle with the extension of second straight trench. A manufacturing method according to the invention for manufacturing a silicon carbide semiconductor device facilitates preventing defects from being causes in a silicon carbide semiconductor device during the manufacture thereof.