Trench Transistor Mesa Edge Deactivation
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Solution Overview
Problem
Trench transistors with closed designs experience leakage currents at the end sides of mesa strips due to source zones extending to these regions, complicating production and affecting device performance.
Innovation Solution
The region of the mesa structure adjoining the edge trench is electrically deactivated by applying a mesa insulation layer and omitting source zones, with the mesa insulation layer serving as a mask for source zone production, allowing for simplified production and reduced leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If source zones are extended to the end sides of mesa strips, then the transistor can be simpler to manufacture, but leakage currents occur at the end sides
Solution Approach 1:
The invention extracts the source zone formation from the end sides of the mesa strips by using the mesa insulation layer as a mask. The insulation layer is selectively removed only in the central region of the mesa strips, preventing source zone formation at the end sides where leakage occurs, while maintaining source zones in the active central regions.
Solution Approach 2:
The invention applies local quality by creating different electrical properties in different regions of the mesa structure. The end sides are kept insulated and inactive, while the central regions have active source zones. This spatial differentiation of electrical activity eliminates leakage paths while preserving transistor functionality.
2Reliability
If source zones reach the end sides of mesa strips, then device coverage is maximized, but the input characteristic curve deteriorates due to leakage
Solution Approach 1:
The source zones are extracted from the problematic end side regions through selective insulation layer removal. This ensures that source zones are present only in the central active regions, maximizing effective device coverage while eliminating the leakage-induced deterioration of the input characteristic curve.
Solution Approach 2:
Different regions of the mesa structure are assigned different functional qualities: the central regions have active source zones for current conduction, while the end sides maintain insulation for leakage prevention. This local differentiation improves both reliability and input characteristic precision.
3Ease of manufacture
If the mesa structure is fully active at the end sides, then manufacturing is simplified, but avalanche strength is reduced due to punch-through effects
Solution Approach 1:
The active source zone formation is extracted from the end side regions by using the mesa insulation layer as a protective mask during doping. This prevents punch-through effects at the end sides, enhancing avalanche strength while maintaining manufacturing simplicity through the reuse of the existing insulation layer.
Solution Approach 2:
The mesa insulation layer serves as a beforehand cushioning measure by being in place before source zone formation. It prevents dopant diffusion into the end side regions, thereby preemptively protecting against punch-through effects and enhancing avalanche strength before the doping process occurs.
4Productivity
If source zones are formed in all mesa regions, then production process is simpler, but dielectric strength is compromised due to active end sides
Solution Approach 1:
The source zone formation is extracted from the end side regions through selective insulation layer removal. This maintains production efficiency by using the existing insulation layer structure rather than adding separate masking steps, while simultaneously protecting dielectric strength by preventing active zones in regions where they would compromise reliability.
Solution Approach 2:
The mesa insulation layer serves multiple functions: it provides electrical insulation, acts as a mask for selective source zone formation, and protects dielectric strength by preventing active zone formation at end sides. This multi-functionality maintains production efficiency while ensuring 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
This approach effectively avoids leakage currents, improves the input characteristic curve, and enhances avalanche strength and reliability of trench power transistors by ensuring the mesa end sides are inactive, thus preventing 'punch-through' and maintaining dielectric strength.
Implementation Method 1
That region of the mesa structure which adjoins the edge trench is at least partly electrically deactivated by virtue of the fact that within this deactivated region a) the mesa structure is covered with a mesa insulation layer
Implementation Method 2
producing an insulation layer covering the mesa structure
Data Source
AI summary
A trench transistor is disclosed. One embodiment has an active zone enclosed by an edge trench, wherein an edge electrode at gate potential is embedded into the edge trench, and the active zone has a mesa structure at least partly adjoining the edge trench. That region of the mesa structure which adjoins the edge trench is at least partly electrically deactivated by virtue of the fact that within this deactivated region a) the mesa structure is covered with a mesa insulation layer, and b) no source zone is provided.