SiC MPS Diode Conduction Area Modulation for Switching Loss Reduction
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Solution Overview
Problem
SiC MPS diodes face challenges in achieving optimal Schottky and p+ ohmic contacts, leading to high static power losses, surge current limitations, and poor switching performance due to large conduction areas during forward and reverse bias operations.
Innovation Solution
The MPS diode design incorporates multiple sets of contacts with varying Schottky barrier heights, Ohmic contact resistances, and threshold voltages, allowing for modulation of the conduction area with forward bias, enabling improved dynamic switching performance across a wide voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the whole Schottky contact region is active from low to high forward currents, then the diode structure is simple, but the switching performance deteriorates with higher leakage currents, higher recovery charge, and slower switching time
Solution Approach 1:
The Schottky contact region is divided into multiple segments with different barrier heights (first Schottky barrier height and second Schottky barrier height). This segmentation allows different regions to conduct at different current levels, reducing the effective conduction area at low currents and improving switching performance while maintaining structural organization.
Solution Approach 2:
Different regions of the Schottky contact are assigned different local properties through varying Schottky barrier heights. The first Schottky barrier height regions handle low-current conduction while the second Schottky barrier height regions handle high-current conduction, optimizing performance across the entire current range without requiring a completely complex structure.
2Power
If the whole PN junction area is active in the whole surge current operation range, then the surge current capability is maximized, but the reverse switching performance degrades
Solution Approach 1:
The PN junction conduction area is made dynamic through the interaction of multiple diodes with different threshold voltages. At low surge currents, only diodes with lower threshold voltages conduct, reducing the active area. At high surge currents, all diodes become active, maximizing surge capability. This dynamic area modulation improves reverse switching performance while maintaining surge current capability.
Solution Approach 2:
The threshold voltage parameter is varied across different PN junctions to create a stepped conduction characteristic. By having diodes with different threshold voltages (first threshold voltage and second threshold voltage), the effective conduction area changes with current level, allowing optimization of both surge current capability and reverse switching performance.
3Reliability
If multiple sets of contacts with varying Schottky barrier heights are implemented, then the conduction area is modulated improving switching performance, but the device complexity increases
Solution Approach 1:
Multiple Schottky contacts with different barrier heights are merged into a single integrated contact structure. This merging approach achieves conduction area modulation and improved switching performance while avoiding the complexity of completely separate contact structures, as all contacts share the same basic Schottky diode architecture and can be fabricated using similar processes.
4Reliability
If multiple sets of contacts with varying Ohmic contact resistances are implemented, then the conduction area is modulated improving switching performance, but the manufacturing complexity increases
Solution Approach 1:
The Ohmic contact resistance parameter is varied across different contact sets to create differentiated conduction paths. By controlling the resistance values (first Ohmic contact resistance and second Ohmic contact resistance), the invention achieves conduction area modulation that improves switching performance while using standard Ohmic contact fabrication techniques, minimizing manufacturing complexity.
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 design enhances switching performance by reducing conduction area, minimizing leakage currents and recovery charge, and improving thermal dissipation, allowing the diode to operate effectively in multiple forward modes with reduced static power losses.
Implementation Method 1
each contact is defined by a Schottky barrier height
Implementation Method 2
the PN junctions associated with the doped contact regions with which the fourth set of contacts are Ohmic contacts have a second threshold voltage
Implementation Method 3
each contact has an Ohmic contact resistance
Data Source
AI summary
The present disclosure relates to a wide band-gap merged p-i-n/Schottky, MPS, diode, and to a method of manufacturing the same. The present disclosure particularly relates to Silicon Carbide, SiC, MPS diodes. According to the present disclosure, the MPS diode includes different Schottky contacts with different IV characteristics, and/or ohmic contacts with a different contact resistance and/or threshold voltage. This allows the conduction area of the MPS diode to change more gradually with forward bias thereby avoiding drawbacks associated with a large conduction area when switching from a forward biasing mode to a reverse biasing mode. Therefore, the dynamic switching performance can be improved in a wide operation voltage range.