IGBT Power Device Floating Gate Reverse Recovery
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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 an n-type floating gate with capacitive coupling and strategically positioned openings in the gate dielectric layer to reduce threshold voltage, allowing for low gate voltage activation and increased reverse current flow, thereby enhancing reverse recovery speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional IGBT structure with body diode is used, then device can conduct reverse current, but reverse recovery time becomes long due to minority carrier injection
Solution Approach 1:
The gate control structure is segmented into multiple independent gates (first gate and second gate) that can independently control different p-n junction diodes. This segmentation allows selective control of reverse current paths, enabling one gate to turn off the body diode while another maintains forward conduction, thereby reducing reverse recovery time without sacrificing reverse conduction capability
Solution Approach 2:
An additional n-type diffusion region is introduced as an intermediary element between the existing structure and the reverse current path. This intermediary region forms a controllable p-n junction diode that acts as a mediator to redirect or suppress reverse current flow through the body diode, reducing minority carrier injection and accelerating reverse recovery while maintaining reverse conduction capability through controlled diode operation
2Reliability
If gate voltage is increased to control current channel, then device turns on reliably, but reverse recovery current increases due to minority carrier injection
Solution Approach 1:
Different gate regions are assigned different functions and voltage levels: the first gate controls the main current channel with higher voltage for reliable turn-on, while the second gate controls the additional p-n junction diode with lower or opposite polarity voltage to suppress reverse current. This local differentiation of gate control qualities allows reliable forward conduction while eliminating the harmful reverse recovery current through localized diode control
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 current through the body diode parasitic and improves reverse recovery speed by enabling low-threshold voltage operation during reverse conduction, facilitating faster switching in IGBT devices.
Implementation Method 1
the n-type floating gate is in contact with one of the two p-type body regions through the first opening to form a p-n junction diode; and a second opening located in the gate dielectric layer, where the n-type floating gate is in contact with the other of the two p-type body regions through the second opening to form the p-n junction diode
Implementation Method 2
an n-type floating gate located above the gate dielectric layer; a gate located above the gate dielectric layer and the n-type floating gate, where the gate covers two side walls of the n-type floating gate in a lateral direction; an insulating dielectric layer between the gate and the n-type floating gate
Data Source
AI summary
Provided is an insulated gate bipolar transistor power device. The IGBT power device includes a gate dielectric layer located above the two p-type body regions and the n-type drift region between the two p-type body regions, an n-type floating gate located above the gate dielectric layer; a gate located above the gate dielectric layer and the n-type floating gate; an insulating dielectric layer between the gate and the n-type floating gate; a first opening located in the gate dielectric layer, where the n-type floating gate is in contact with one of the two p-type body regions through the first opening to form a p-n junction diode; and a second opening located in the gate dielectric layer, where the n-type floating gate is in contact with the other of the two p-type body regions through the second opening to form the p-n junction diode.