Trench-Gate IGBT Layout for di/dt Control and Oscillation Suppression
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Solution Overview
Problem
Conventional insulated gate bipolar transistors (IGBTs) and reverse conducting IGBTs (RC-IGBTs) face issues with di/dt controllability during turn ON and oscillation of current waveforms due to charge storage regions.
Innovation Solution
A semiconductor device with a trench-gate structure where the proportion of gate trenches relative to total trenches is set between 60% to 84%, and dummy trenches are used to reduce hole density and parasitic capacitance, enhancing di/dt controllability and suppressing oscillation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a charge storage region is provided in the n--type drift region to increase injection enhanced effects and reduce conduction loss, then conduction loss is reduced, but di/dt controllability deteriorates and current waveform oscillation occurs
Solution Approach 1:
The patent divides the trench structure into two types: gate trenches (containing gate electrodes) and dummy trenches (without gate electrodes). This segmentation allows the charge storage function to be distributed across both types of trenches, while the dummy trenches specifically address the oscillation issue by providing controlled charge storage without the full gate control structure, thus improving di/dt controllability while maintaining conduction loss reduction
Solution Approach 2:
The patent applies different structures to different locations: gate trenches are positioned in regions where full gate control is needed, while dummy trenches are positioned in regions where controlled charge storage is beneficial for reducing oscillation. The local variation in trench types creates optimal performance in different areas of the device
2Reliability
If the gate trench ratio is increased to improve di/dt controllability, then di/dt controllability is improved, but conduction loss increases
Solution Approach 1:
The patent uses dummy trenches that provide partial charge storage functionality without the complete gate structure. This partial action allows the device to achieve improved di/dt controllability while maintaining lower conduction loss, as the dummy trenches contribute to oscillation suppression without the full control overhead of complete gate trenches
3Reliability
If dummy trenches are added to reduce hole density and parasitic capacitance, then di/dt controllability is improved, but device complexity increases
Solution Approach 1:
The dummy trenches are essentially copies of the gate trench structure but without the gate electrode component. This copying approach allows the device to benefit from the charge storage and oscillation suppression effects while avoiding the complexity of designing and fabricating entirely new structures, as the dummy trenches follow the same geometric pattern as the gate trenches
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 proposed semiconductor device improves di/dt controllability for current between the collector and emitter during turn ON, suppresses oscillation, and reduces conduction loss by optimizing the trench gate ratio and using dummy trenches.
Implementation Method 1
dummy trenches are used to reduce hole density and parasitic capacitance
Data Source
AI summary
A semiconductor device is an IGBT of a trench-gate structure and has a storage region directly beneath a p−-type base region. The semiconductor device has gate trenches and dummy trenches as trenches configuring the trench-gate structure. An interval (mesa width) at which the trenches are disposed is in a range of 0.7 μm to 2 μm. In each of the gate trenches, a gate electrode of a gate potential is provided via a first gate insulating film. In each of the dummy trenches, a dummy gate electrode of an emitter potential is provided via a second gate insulating film. A total number of the gate electrode is in a range of 60% to 84% of a total number of the dummy electrodes.