RC-IGBT Diode Region Width and Contact Area Optimization
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Solution Overview
Problem
In RC-IGBTs, the flow of holes from the IGBT body region into the diode drift region causes instability in the forward voltage of the diode due to gate interference, leading to deteriorated reverse recovery properties and slowed response speed.
Innovation Solution
Widening the diode region width to greater than 200µm and maintaining a smaller anode contact area ratio compared to the body contact area ratio reduces the influence of gate interference and hole density in the drift region, thereby stabilizing the forward voltage and improving reverse recovery properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the contact portion of the body region is made smaller than the contact portion of the anode region to suppress gate interference, then the influence of gate interference is mitigated, but the hole density in the drift region becomes high which deteriorates reverse recovery property
Solution Approach 1:
The patent applies local quality by creating different contact area ratios in different regions: the anode contact portion has a smaller area ratio (5% or less) while the body contact portion has a larger area ratio (15% or more). This localized differentiation allows the anode region to supply sufficient holes for low forward voltage while the overall device structure maintains good reverse recovery characteristics through the balanced body region contact distribution.
2Power
If holes flow into the drift region from the body region upon diode conduction, then the forward voltage drops, but when gate voltage is applied during diode conduction, the number of holes decreases and forward voltage rises causing instability
Solution Approach 1:
The patent applies parameter changes by optimizing the contact area ratios of different regions. By setting the anode contact area ratio to 5% or less and the body contact area ratio to 15% or more, the device parameters are tuned to achieve a balance where sufficient holes are supplied to maintain low forward voltage while the distribution pattern prevents excessive hole accumulation that would cause gate interference and forward voltage instability.
3Power
If the anode contact portion area is large, then holes flow in high density into the drift region which improves forward voltage, but the reverse recovery property deteriorates due to high hole density
Solution Approach 1:
The patent applies local quality by creating different contact area ratios in different regions: the anode contact portion has a smaller area ratio (5% or less) while the body contact portion has a larger area ratio (15% or more). This localized differentiation allows the anode region to supply sufficient holes for low forward voltage while the overall device structure maintains good reverse recovery characteristics through the balanced body region contact distribution.
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
The solution effectively reduces the impact of gate interference on the diode's forward voltage stability and enhances the diode's response speed by increasing the main current flow while minimizing parasitic current and reverse current density.
Implementation Method 1
holes flow into a drift region of a diode from a body region of an IGBT adjacent to the diode upon when the diode is electrically conducted
Implementation Method 2
when an on-voltage is applied to a gate of the IGBT during the electric conduction of the diode, a number of the holes flowing into the drift region of the diode from the body region of the IGBT decreases
Data Source
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AI summary
An influence of a gate interference is suppressed and a reverse recovery property of a diode is improved. A diode includes a diode region located between the first boundary trench and the second boundary trench and a first and second IGBT regions. An emitter region and a body region are provided in each of the first and second IGBT regions. Each body region includes a body contact portion. An anode region is provided in the diode region. The anode region includes an anode contact portion. An interval between the first and second boundary trenches is equal to or longer than 200 µm. An area ratio of the anode contact portion in the diode region is lower than each of an area ratio of the body contact portion in the first IGBT region and an area ratio of the body contact portion in the second IGBT region.