Parallel Diode Semiconductor Structure for Lower Reverse Recovery Loss
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Solution Overview
Problem
Existing semiconductor devices with parallel transistor and diode configurations face challenges in optimizing loss characteristics and suppressing peak current during reverse recovery due to variations in diode resistivity and area, leading to increased surge voltage and oscillation.
Innovation Solution
The semiconductor device incorporates first and second diode portions with different resistivities and areas, separated by a separation well region, and includes lifetime killers to control carrier lifetime, allowing for adjusted characteristics and reduced peak current through differential doping concentrations and resistances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If diode portions with different resistivities are provided in parallel, then reverse recovery loss is reduced, but device structure becomes more complex
Solution Approach 1:
The diode function is segmented into two distinct diode portions with different resistivities (first diode portion with higher resistivity and second diode portion with lower resistivity). During reverse recovery, the higher resistivity diode portion suppresses peak current while the lower resistivity diode portion conducts the reverse recovery current, thereby reducing reverse recovery loss. This segmentation allows each diode portion to specialize in different aspects of reverse recovery behavior.
Solution Approach 2:
Different regions of the semiconductor device are assigned different electrical characteristics through selective doping. The first diode portion has higher resistivity in its drift region compared to the second diode portion, creating local quality differences. This enables each diode portion to contribute differently to the overall reverse recovery process, with the higher resistivity region suppressing peak current and the lower resistivity region providing efficient current conduction path.
2Loss of energy
If diode area is increased to reduce forward voltage drop, then conduction loss decreases, but peak current during reverse recovery increases
Solution Approach 1:
The total diode area is segmented between two diode portions with different resistivity characteristics. The first diode portion with higher resistivity has an optimized area that balances forward conduction loss with peak current suppression during reverse recovery. The second diode portion with lower resistivity provides an additional conduction path that reduces overall forward voltage drop while its lower area prevents excessive peak current generation.
Solution Approach 2:
The resistivity parameter of the drift region is varied between the two diode portions to achieve different electrical characteristics. The first diode portion uses higher resistivity material to suppress peak current, while the second diode portion uses lower resistivity material to reduce forward voltage drop. This parameter variation allows the device to simultaneously achieve low conduction loss and controlled peak current during reverse recovery.
3Ease of manufacture
If uniform doping concentration is used in diode portions, then manufacturing is simpler, but loss characteristics cannot be optimized
Solution Approach 1:
Different doping concentrations are applied to different diode portions to create local quality differences. The first diode portion receives doping that creates higher resistivity in the drift region, while the second diode portion receives doping that creates lower resistivity. This local quality variation enables optimization of power loss characteristics by allowing each diode portion to contribute differently to conduction and reverse recovery losses.
Solution Approach 2:
The doping concentration parameter is changed between different diode portions to achieve desired resistivity values. By controlling the doping concentration in the drift region of each diode portion, the device can optimize the balance between forward conduction loss and reverse recovery loss. This parameter change is achieved through selective doping processes that target specific diode portions during manufacturing.
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 effectively suppresses peak current and oscillation during reverse recovery, reducing on-state power loss and reverse recovery loss while maintaining prescribed diode characteristics.
Implementation Method 1
The first diode portion and the second diode portion may each have an anode region of a second conductivity type provided between the drift region and the upper surface of the semiconductor substrate. The first diode portion may be separated from the second diode portion by a separation well region of the second conductivity type having a higher doping concentration than the anode region
Implementation Method 2
In at least one of the first diode portion and the second diode portion, lifetime killers controlling a carrier lifetime may be provided inside the semiconductor substrate. The concentration of the lifetime killers in the first diode portion may be different from that in the second diode portion.
Data Source
AI summary
A semiconductor device is preferably excellent in characteristics such as a loss characteristic. Provided is a semiconductor device including a semiconductor substrate, including an upper-surface electrode provided on an upper surface of the semiconductor substrate; an lower-surface electrode provided on a lower surface of the semiconductor substrate; a transistor portion provided in the semiconductor substrate and connected to the upper-surface electrode and the lower-surface electrode; a first diode portion provided in the semiconductor substrate and connected to the upper-surface electrode and the lower-surface electrode; and a second diode portion provided in the semiconductor substrate and connected to the upper-surface electrode and the lower-surface electrode, wherein the first diode portion and the second diode portion have different resistivities in a depth direction of the semiconductor substrate.