IGBT Diode Forward Voltage Stability via Segmented Grooves
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Solution Overview
Problem
The existing semiconductor devices with insulating gate bipolar transistors (IGBTs) and free wheel diodes face issues where the forward-direction breakdown voltage (VF) of the diodes increases when the IGBT gates turn on, and the recovery current is not adequately reduced.
Innovation Solution
The semiconductor device design includes paired grooves that isolate IGBT and diode areas, with emitter regions only between the grooves, and additional grooves outside the emitter regions to moderate the electric field, preventing VF increase and reducing recovery current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If emitter regions are formed across the entire P base layer, then the IGBT can control current effectively, but the diode's forward-direction breakdown voltage increases when the IGBT gate turns on
Solution Approach 1:
The P base layer is divided into multiple regions by grooves, with emitter regions selectively formed only in specific areas between the grooves. This segmentation isolates the IGBT emitter regions from the diode areas, preventing the diode's forward voltage from increasing when the IGBT gate turns on, while maintaining effective current control capability.
2Loss of energy
If helium ions are implanted into the N layer to shorten carrier lifetime, then recovery current is reduced, but the diode's forward voltage increase becomes greater when the IGBT gate turns on
Solution Approach 1:
The grooves segment the P base layer to create isolated emitter regions, which prevents the harmful interaction between the helium ion-implanted N layer and the diode operation. This allows recovery current to be reduced through helium ion implantation without causing excessive forward voltage increase in the diode when the IGBT gate turns on.
Solution Approach 2:
Helium ions are implanted into the N layer in specific local areas to shorten carrier lifetime and reduce recovery current, while the groove structure ensures that this local modification does not adversely affect the diode's forward voltage characteristics when the IGBT is operating.
3Ease of manufacture
If grooves are formed to isolate IGBT and diode areas, then diode forward voltage stability is improved, but the device structure becomes more complex
Solution Approach 1:
Grooves are formed to segment the P base layer into isolated regions, creating distinct areas for IGBT emitter regions and diode structures. This segmentation effectively stabilizes the diode's forward voltage by preventing electrical interaction with the IGBT gate, while the groove structure itself is a relatively simple geometric feature that can be integrated into standard semiconductor manufacturing processes.
Data Source
AI summary
A semiconductor device, including: a semiconductor substrate of a first conductivity type having a first and second major surfaces; a first conductivity type semiconductor layer formed on the first major surface of the semiconductor substrate; a base layer of a second conductivity type formed on the first major surface of the semiconductor layer and separated by the semiconductor layer from the semiconductor substrate; a pair of groove portions penetrating the base layer from the first major surface and reaching at least the semiconductor layer; an insulation film disposed inside the groove portion and a gate electrode formed inside the groove portion through the insulation film; a first conductivity type semiconductor layer and a second conductivity type semiconductor layer formed on the second major surface of the semiconductor substrate; and an emitter region disposed on the first major surface of the base layer and along the groove portions, wherein a transistor controlling a current flowing in the base layer by the gate electrode and a diode made of the semiconductor layer and the base layer are disposed within the semiconductor device, and the emitter region is disposed only in an area which is between the pair of groove portions.