Trench Gate IGBT Base Layout for Turn-On and dV/dt Control
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Solution Overview
Problem
Trench gate insulated gate bipolar transistors (IGBTs) face challenges in controlling turn-on speed and adjusting capacitance ratios due to difficulties in forming hole extraction paths, leading to increased switching losses and voltage change rates during switching processes.
Innovation Solution
The IGBT design includes a drift layer, an accumulation layer with higher impurity concentration, a base layer with active and floating base regions, and a dummy trench structure, where the active and floating base regions are alternately arranged via a base isolation region, allowing for controlled hole extraction and reduced switching losses by moderating potential changes during switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a floating base region is used to decrease on-voltage through injection enhancement, then on-voltage decreases, but hole extraction path formation becomes difficult and turn-on speed control deteriorates
Solution Approach 1:
The base region is segmented into multiple regions with different functions: the first base region (connected to emitter potential) provides hole extraction path and turn-on control, while the second base region (floating potential) provides injection enhancement for low on-voltage. This segmentation allows each region to independently perform its specific function without interfering with the other.
Solution Approach 2:
The gate trench acts as an intermediary structure that enables both hole extraction and turn-on control. By forming the gate trench to extend through both base regions, it creates extraction paths in the first base region while allowing the second base region to maintain floating potential for injection enhancement.
2Loss of energy
If hole extraction path is formed around gate trench to improve turn-off characteristics, then turn-off loss decreases, but turn-on speed becomes difficult to control
Solution Approach 1:
The base region is divided into a first base region that provides hole extraction paths for turn-off and a second base region that maintains floating potential for fast turn-on. This segmentation allows independent optimization of turn-off and turn-on characteristics without mutual interference.
3Loss of energy
If floating base region is used to decrease on-voltage, then on-voltage decreases, but dV/dt control and switching loss management deteriorate
Solution Approach 1:
The segmented base region structure with first and second base regions enables independent control of dV/dt and switching loss while maintaining low on-voltage. The first base region connected to emitter potential provides control stability, while the second floating base region provides injection enhancement.
4Loss of energy
If base region is separated by gate trench and dummy trench with floating base region, then switching loss improves, but hole extraction path formation becomes difficult
Solution Approach 1:
The base region is segmented into first and second base regions separated by the gate trench. The first base region is configured to form hole extraction paths around the gate trench, while the second base region maintains floating potential. This segmentation enables both switching loss reduction and effective hole extraction path formation.
Solution Approach 2:
The gate trench serves as an intermediary structure that facilitates hole extraction in the first base region while allowing the second base region to maintain floating potential for injection enhancement, thus enabling both functions to coexist.
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 design enhances turn-on characteristics, reduces switching losses, and allows for adjustable capacitance ratios, enabling efficient voltage control and wide-range applicability by suppressing hole extraction and moderating voltage change rates.
Implementation Method 1
the on-voltage can be decreased by the injection enhancement (IE) effect by the floating base region
Data Source
AI summary
IGBT includes an n-type drift layer, an n-type accumulation layer provided on the upper surface of the drift layer having higher impurity concentration than the drift layer, a base layer provided on the upper surface of the accumulation layer, a gate electrode embedded inside a striped gate trench penetrating the base layer and the storage layer through a gate insulating film, and a dummy electrode embedded inside a dummy trench provided to face the gate trench across the base layer and the accumulation layer through a dummy insulating film. The base layer has a p-type active base region and a p-type floating base region arranged alternately in the extending direction of the gate trench, and an n-type base isolation region isolating the active base region and the floating base region.