Compound Semiconductor Trench Gate Field Management
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Solution Overview
Problem
In compound semiconductor devices with trench gate structures, the formation of a deep p-type layer to prevent dielectric breakdown leads to increased on-resistance due to electric field concentration at trench corners, necessitating a trade-off between breakdown voltage and on-resistance.
Innovation Solution
A compound semiconductor device with a semiconductor substrate featuring a deep trench having a first conductivity type region at its corner portion, forming a triangular or rounded triangular shape to reduce electric field strength and prevent breakdown voltage deterioration, allowing the p-type deep layer to be formed without increasing on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the p-type deep layer is made deeper to reduce electric field applied to gate insulation layer, then breakdown voltage is improved, but on-resistance increases due to increased JFET portion
Solution Approach 1:
The patent applies local quality by forming a first conductivity type region (e.g., n-type region) at the corner portion of the deep trench bottom, creating a localized modification rather than uniformly changing the entire deep layer structure. This localized approach reduces electric field concentration at the critical corner area without requiring an overall increase in deep layer depth, thereby avoiding the trade-off between breakdown voltage and on-resistance.
Solution Approach 2:
The patent employs curvature by forming a first conductivity type region with a rounded or curved cross-section at the corner portion of the deep trench bottom. This curved geometry eliminates the sharp corner that causes electric field concentration, distributing the electric field more evenly and reducing peak field strength without increasing the deep layer depth, thus preventing on-resistance increase.
2Ease of manufacture
If the p-type deep layer is formed at uniform concentration by epitaxial growth, then manufacturing is simplified, but electric field strength at off-time becomes high at corner portion causing breakdown voltage deterioration
Solution Approach 1:
The patent maintains the simplicity of uniform epitaxial growth for the deep layer while adding a localized first conductivity type region at the corner portion. This localized modification can be achieved through targeted doping or selective epitaxial growth, preserving the overall manufacturing simplicity while addressing the electric field concentration issue at the critical corner area.
Solution Approach 2:
The patent applies preliminary action by forming the first conductivity type region at the corner portion before final device operation. This pre-formed region proactively reduces electric field concentration at the corner, preventing breakdown voltage deterioration before it occurs, while maintaining the straightforward uniform epitaxial growth process for the main deep layer structure.
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 configuration restricts the increase in electric field strength and on-resistance, maintaining high breakdown voltage without the need for a deeper p-type deep layer, thus optimizing the device's performance.
Implementation Method 1
a cross section of the first conductivity type region is a triangular shape or a rounded triangular shape in which a portion of the first conductivity type region being in contact with the deep layer is recessed to have a curved surface
Data Source
AI summary
A compound semiconductor device includes a semiconductor substrate having a ground layer of a first conductivity type made of a compound semiconductor, a first conductivity type region formed at a corner portion of a bottom of a deep trench formed to the ground layer, and a deep layer of a second conductivity type formed in the deep trench so as to cover the first conductivity type region. A cross section of the first conductivity type region is a triangular shape or a rounded triangular shape in which a portion of the first conductivity type region being in contact with the deep layer is recessed to have a curved surface.