Recessed Trench Gate Corners for MOSFET and IGBT Breakdown Voltage
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Solution Overview
Problem
Current trench gate structures in MOSFET and IGBT devices face challenges in balancing on-state resistance (Ron), breakdown voltage (BV), and oxide thickness, requiring complex processes and structures to achieve optimal performance.
Innovation Solution
A trench gate structure with a recessed bottom corner having an internal angle less than 90°, formed using anisotropic and isotropic etching techniques, which allows for a simpler process to balance Ron, BV, and oxide thickness without the need for a rounded angle or super junction structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional right-angle trench gate structure is used, then the manufacturing process is simple, but the breakdown voltage is insufficient and oxide reliability is poor
Solution Approach 1:
The patent applies asymmetry by creating a non-uniform trench gate structure where the bottom corners are rounded with a specific radius (R1) while the sidewalls maintain a different geometry. This asymmetric design concentrates the stress relief and oxide thickness improvement at the critical bottom corner regions without requiring complex overall structure changes, thereby improving oxide reliability while maintaining manufacturing simplicity
Solution Approach 2:
The patent implements spheroidality by rounding the bottom corners of the trench gate with a specific radius (R1). This curvature eliminates the sharp 90-degree corners that cause stress concentration and thin oxide formation, allowing the oxide layer to grow uniformly and achieve greater thickness at the critical bottom corner regions, thus improving breakdown voltage and oxide reliability
2Reliability
If the trench bottom width is increased, then oxide diffusion is improved, but on-state resistance increases
Solution Approach 1:
The patent applies local quality by rounding only the bottom corners of the trench gate with a specific radius (R1) while keeping the rest of the trench structure relatively simple. This localized geometric modification improves oxide growth and stress distribution at the critical bottom corner regions without significantly increasing the overall trench bottom width, thereby maintaining low on-state resistance while improving oxide reliability
3Reliability
If a rounded bottom structure is used, then oxide thickness at corners is improved, but manufacturing complexity increases
Solution Approach 1:
The patent implements spheroidality by rounding the bottom corners of the trench gate with a specific radius (R1). This curvature eliminates the sharp 90-degree corners that cause stress concentration and thin oxide formation, allowing the oxide layer to grow uniformly and achieve greater thickness at the critical bottom corner regions, thus improving breakdown voltage and oxide reliability
4Reliability
If complex structures like super junction are used, then breakdown voltage and on-state resistance are improved, but manufacturing complexity and process length increase
Solution Approach 1:
The patent applies asymmetry by creating a non-uniform trench gate structure where the bottom corners are rounded with a specific radius (R1) while the sidewalls maintain a different geometry. This asymmetric design concentrates the stress relief and oxide thickness improvement at the critical bottom corner regions without requiring complex overall structure changes, thereby improving oxide reliability while maintaining manufacturing simplicity
Solution Approach 2:
The patent implements spheroidality by rounding the bottom corners of the trench gate with a specific radius (R1). This curvature eliminates the sharp 90-degree corners that cause stress concentration and thin oxide formation, allowing the oxide layer to grow uniformly and achieve greater thickness at the critical bottom corner regions, thus improving breakdown voltage and oxide reliability
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 recessed trench gate structure effectively increases breakdown voltage, reduces on-state resistance, and enhances oxide reliability, while simplifying the manufacturing process for VDMOS and IGBT devices, applicable to silicon, silicon carbide, and gallium nitride-based power devices.
Implementation Method 1
formed using anisotropic and isotropic etching techniques
Implementation Method 2
formed using anisotropic and isotropic etching techniques
Implementation Method 3
oxide on a (110) crystal face of a trench sidewall is thicker than that on a trench bottom
Data Source
AI summary
The present invention provides a device having a trench gate structure and a method of making the same. The device comprises a substrate, a drift region, a well region, a trench gate, a heavily-doped region, and an electrode positioned on the heavily-doped region. The structure of the device is simple to provide good VDMOS and IGBT breakdown voltages, and meanwhile take on-state resistance and reliability of oxide into account.