IGBT Diode Gate Segmentation for Conduction Loss Reduction
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Solution Overview
Problem
Conventional semiconductor devices experience high conduction loss and reduced breakdown voltage due to the formation of inversion layers in diode elements when turn-on voltage is applied, leading to inefficient operation in inverter circuits.
Innovation Solution
The semiconductor device features independently controlled gate electrodes in both IGBT and diode regions, with a voltage applied to the diode region's gate electrodes that does not form an inversion layer, allowing electrons to flow through the base layer and inject holes into the drift layer, reducing conduction loss and maintaining breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If turn-on voltage is applied to gate electrodes in diode region, then inversion layer is formed enabling IGBT operation, but conduction loss increases due to blocked electron flow through base layer
Solution Approach 1:
The gate electrode structure is segmented into two independent parts: a first gate electrode in the IGBT region and a second gate electrode in the diode region. This segmentation allows independent voltage control, enabling the diode region gate to be held at a voltage that prevents inversion layer formation while the IGBT region gate receives turn-on voltage, thus maintaining electron flow through the base layer and reducing conduction loss.
Solution Approach 2:
Different voltage conditions are applied to different regions: the IGBT region receives turn-on voltage to form inversion layer for switching operation, while the diode region is maintained at a voltage below the threshold to avoid inversion layer formation. This local differentiation of electrical conditions optimizes each region's function - IGBT for switching and diode for low-loss conduction.
2Loss of energy
If no trench is formed in diode region, then conduction loss is reduced, but breakdown voltage decreases due to electric field concentration
Solution Approach 1:
The trench structure is segmented such that trenches are formed in both the IGBT region and the diode region. This segmentation allows the diode region to have trench structures that prevent electric field concentration and maintain high breakdown voltage, while the overall device architecture still enables low conduction loss through independent gate control that prevents unnecessary inversion layer formation.
Solution Approach 2:
The trench structure is locally applied in the diode region to address the specific problem of electric field concentration at the trench edges. This local structural modification enhances the breakdown voltage in the diode region without affecting the overall conduction characteristics, which are controlled by the independent gate electrode voltage application.
3Device complexity
If common gate pad is used for both IGBT and diode regions, then device complexity is reduced, but independent control capability is lost
Solution Approach 1:
The gate control system is segmented into two independent control paths: one for the first gate electrode in the IGBT region and another for the second gate electrode in the diode region. This segmentation provides independent voltage control capability, allowing the device to adapt to different operating conditions - such as applying turn-on voltage to IGBT while keeping diode gate at zero voltage - without increasing overall device complexity significantly.
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 conduction loss in diode elements and restricts the reduction of breakdown voltage by allowing electron flow through the base layer and hole injection, enhancing the semiconductor device's performance in power switching applications.
Implementation Method 1
when a voltage lower than the lower electrode is applied to the upper electrode, and a turn-on voltage is applied to the gate electrode, an inversion layer (i.e., a channel) having the N conductive type is formed in a portion of the base layer contacting the trench
Implementation Method 2
a hole is supplied from the collector layer to the drift layer. Thus, a resistance of the drift layer is reduced due to conductivity modulation
Implementation Method 3
the electron in the drift layer is discharged to the upper electrode via the base layer; and the hole is injected into the drift layer from the base layer when the electron passes through the base layer
Data Source
AI summary
A semiconductor device includes: a drift layer; a base layer on the drift layer; a collector layer and a cathode layer opposite to the base layer; multiple trenches penetrating the base layer; a gate electrode in each trench; an emitter region in a surface portion of the base layer and contacting each trench; a first electrode connected to the base layer and the emitter region; and a second electrode connected to the collector layer and the cathode layer. The gate electrodes in a diode region of a semiconductor substrate are controlled independently from the gate electrodes in the IGBT region. A voltage not forming an inversion layer in the base layer is applied to the gate electrodes in the diode region.