IGBT Hole Extraction Region for Switching Loss Reduction
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Solution Overview
Problem
Insulated gate bipolar transistors (IGBTs) experience increased collector voltage and tail current when switching from on-state to off-state, leading to elevated switching losses due to excessive electron and hole accumulation in the n-type drift region, which hampers the performance of semiconductor devices.
Innovation Solution
The semiconductor device incorporates a first and second transistor configuration, where the second transistor allows hole flow only during the off-state transition, utilizing a p-type hole extraction region to effectively discharge accumulated holes to the emitter electrode, reducing tail current and switching losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the concentration of holes in the drift region is increased to promote the injection enhancement effect, then the resistance in the drift region decreases and on-voltage is reduced, but a pnp parasitic bipolar transistor is brought into the on-state resulting in latch-up
Solution Approach 1:
The device is divided into two separate transistors: a first transistor for normal IGBT operation and a second transistor specifically for hole extraction. This segmentation allows the second transistor to remove excess holes from the drift region without triggering latch-up, while the first transistor maintains low on-voltage through the injection enhancement effect.
Solution Approach 2:
The second transistor acts as an intermediary mechanism that selectively removes holes from the drift region. By controlling hole concentration through this intermediary structure, the patent achieves low on-voltage operation while preventing parasitic transistor activation and latch-up conditions.
2Loss of energy
If an n-type barrier region is inserted between the n-type drift region and p-type base region to increase charge concentration, then the injection enhancement effect is promoted, but the device complexity increases
Solution Approach 1:
Instead of inserting an additional barrier region layer, the patent segments the existing emitter into two functional regions. This achieves the same charge concentration effect without adding structural complexity, as the segmentation uses existing device layers rather than introducing new material layers.
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 reduces switching losses and maintains the excess accumulation effect, thereby improving the performance of IGBTs by minimizing on-voltage and switching losses while ensuring efficient hole discharge.
Implementation Method 1
a current composed of holes flows from the n−− drift region through the hole extraction region and the second transistor to the emitter electrode
Implementation Method 2
a current composed of electrons and holes flows from the collector electrode through the first transistor to the emitter electrode
Data Source
AI summary
An IGBT (50) includes a p+ collector region (3) and an n−− drift region (1), in which a first transistor (TR1) and a second transistor (TR2) are formed on the n−− drift region (1). In the n−− drift region (1), a p-type hole extraction region (14) is formed in contact with the second transistor (TR2). When the IGBT (50) is in an on-state, electrons and holes flow through the first transistor (TR1), but a current does not flow through the second transistor (TR2). On the other hand, when the IGBT (50) is switched from the on-state to an off-state, holes flow through the first transistor (TR1), and holes flow through the hole extraction region (14) and the second transistor (TR2).