IGBT Device With Floating Gate Diode For Reverse Recovery Control
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Solution Overview
Problem
IGBT devices experience long reverse recovery times due to minority carrier injection, leading to significant reverse recovery currents.
Innovation Solution
The IGBT device incorporates a MOSFET cell array with a p-n junction diode structure, where the n-type floating gate is isolated by a gate dielectric layer and capacitive coupling is used to adjust the reverse recovery speed by controlling the number of MOSFET cells with p-n junction diodes, allowing for efficient adjustment of the reverse recovery speed and reduced manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the IGBT device uses a conventional structure with body diode parasitic, then the device can operate as an IGBT, but the reverse recovery time becomes long due to minority carrier injection
Solution Approach 1:
The patent segments the gate structure into two independent gates: a first gate (gate electrode) and a second gate (floating gate). This segmentation allows independent control of the MOSFET channel and the body diode, enabling the body diode to be turned off before the MOSFET channel, thereby reducing reverse recovery time caused by minority carrier injection.
Solution Approach 2:
The patent applies preliminary action by using the first gate to turn off the body diode before turning off the MOSFET channel. This preliminary action of closing the body diode prevents minority carrier injection that would otherwise occur when the MOSFET channel turns off, thus reducing reverse recovery time.
2Adaptability or versatility
If the gate structure uses a conventional single-gate design, then the device structure is simple, but the reverse recovery speed cannot be adjusted
Solution Approach 1:
The patent introduces dynamics by making the gate structure adjustable through a dual-gate design. The first gate electrode can be controlled to adjust the reverse recovery speed of the body diode, providing dynamic control over the device's reverse recovery characteristics without requiring complete structural redesign.
Solution Approach 2:
The patent applies universality by designing the gate structure to perform multiple functions: the first gate controls both the MOSFET channel and the body diode, while the second gate (floating gate) provides additional control capability. This multi-functional gate structure enables adjustment of reverse recovery speed while maintaining IGBT operation.
3Manufacturing precision
If the n-type floating gate contacts the p-type body region to form a p-n junction diode, then the reverse recovery speed can be adjusted, but the manufacturing process becomes more complex
Solution Approach 1:
The patent applies local quality by creating a specific local structure where the n-type floating gate contacts the p-type body region to form a p-n junction diode. This localized structural modification enables precise control of reverse recovery characteristics in a specific region without requiring complex changes to the entire device structure.
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 allows for convenient and accurate adjustment of reverse recovery speed, reducing reverse recovery currents and extending the device's application range while minimizing manufacturing costs.
Implementation Method 1
the gate electrode acts on the n-type floating gate through capacitive coupling
Data Source
AI summary
Provided is an IGBT device. The IGBT device includes an MOSFET cell array, where each MOSFET cell includes a p-type body region located at the top of an n-type drift region, an n-type emitter region located in the p-type body region, and a gate dielectric layer, a gate electrode and an n-type floating gate which are located above the p-type body region. The gate electrode is located above the gate dielectric layer, the n-type floating gate is located above the gate dielectric layer, and the gate electrode acts on the n-type floating gate through capacitive coupling. The n-type floating gate of at least one MOSFET cell is isolated from the p-type body region through the gate dielectric layer, and the n-type floating gate of at least one MOSFET cell contacts the p-type body region through an opening in the gate dielectric layer to form a p-n junction diode.