Monolithic RC Snubber Using Junction Termination Edge for SiC MOSFETs
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Solution Overview
Problem
High power and high voltage transistors, such as SiC MOSFETs, experience undesirable commutation oscillations due to rapid switching, leading to electromagnetic interference and inefficiencies, which existing external RC snubbers attempt to mitigate but introduce leakage inductance and increased switching losses.
Innovation Solution
An RC snubber is integrated monolithically with the unipolar power transistor on the same semiconductor substrate, eliminating parasitic inductance and reducing area consumption, using a poly silicon resistor and capacitor formed from junction termination edge materials to effectively dampen oscillations without external components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If external RC snubbers are used to dampen oscillations, then oscillation damping is improved, but leakage inductance and switching losses increase
Solution Approach 1:
The RC snubber circuit is merged with the power transistor by forming both structures monolithically on the same semiconductor substrate. The capacitor is formed as part of the junction termination edge, and the resistor is integrated within the transistor structure, eliminating the need for external snubber components and reducing parasitic inductance while maintaining oscillation damping capability
Solution Approach 2:
The junction termination edge serves as an intermediary structure that dual-purpose: it provides electrical field termination for high voltage operation and simultaneously forms the capacitor of the RC snubber circuit. This eliminates the need for separate external capacitor components and reduces parasitic inductance
2Stability of the object's composition
If external RC snubbers are used to dampen oscillations, then oscillation damping is improved, but device area consumption increases
Solution Approach 1:
The RC snubber circuit is merged with the power transistor by forming both structures monolithically on the same semiconductor substrate. The capacitor is formed as part of the junction termination edge, and the resistor is integrated within the transistor structure, eliminating the need for external snubber components and reducing parasitic inductance while maintaining oscillation damping capability
Solution Approach 2:
The junction termination edge is given multiple functions: it provides electrical field termination for high voltage operation and simultaneously serves as the capacitor structure for the RC snubber. This multi-functionality eliminates the need for separate external components and reduces overall device area
3Stability of the object's composition
If external RC snubbers are used to dampen oscillations, then oscillation damping is improved, but parasitic inductance increases
Solution Approach 1:
The RC snubber circuit is merged with the power transistor by forming both structures monolithically on the same semiconductor substrate. The capacitor is formed as part of the junction termination edge, and the resistor is integrated within the transistor structure, eliminating the need for external snubber components and reducing parasitic inductance while maintaining oscillation damping capability
Solution Approach 2:
The junction termination edge serves as an intermediary structure that dual-purpose: it provides electrical field termination for high voltage operation and simultaneously forms the capacitor of the RC snubber circuit. This eliminates the need for separate external capacitor components and reduces parasitic inductance
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 integration reduces leakage inductance, minimizes area usage, and scales well with the number of transistors, providing efficient damping of oscillations while maintaining high voltage handling capabilities and reducing switching losses.
Implementation Method 1
The capacitor is between a poly silicon structure and the semiconductor substrate, and is part of the junction termination edge. The capacitor comprises a p-n junction.
Implementation Method 2
If a load current in one of these transistors is switched off quickly, commutation oscillations may be triggered. The commutation oscillations can result in electromagnetic interference
Implementation Method 3
The RC snubber comprises a poly silicon resistor. The poly silicon resistor is between a source of the unipolar power transistor and a first layer forming the capacitor.
Implementation Method 4
Operation of these transistors may result in relatively high commutation inductances, such as in the range of 20nH - 100nH per commutation path. If a load current in one of these transistors is switched off quickly, commutation oscillations may be triggered.
Implementation Method 5
External RC snubbers attempt to mitigate but introduce leakage inductance and increased switching losses. This integration reduces leakage inductance
Data Source
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AI summary
An apparatus includes a junction termination edge (260), a unipolar power transistor, and an RC snubber (201). The RC snubber has a capacitor (220) between a poly silicon structure (221) and a semiconductor substrate (212), and part of the junction termination edge. The capacitor has a p-n junction. The RC snubber has a poly silicon resistor (218) between a source (244) of the unipolar power transistor and a first layer (210) forming the capacitor. The unipolar transistor and the RC snubber are coupled in parallel. The RC snubber and the unipolar power transistor are formed monolithically on the semiconductor substrate.