SiC Metallization Stack With Copper Barrier for High Power Density
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Solution Overview
Problem
Silicon carbide power devices face limitations in achieving high power densities and thermal robustness due to material constraints, particularly in maintaining effective thermal management and preventing premature aging from high operational temperatures.
Innovation Solution
A silicon carbide device with a nickel-silicon-aluminum contact layer, a titanium-tungsten barrier layer, and a copper metallization layer is developed, which forms an ohmic connection and provides a diffusion barrier, enabling high power density and improved thermal robustness by preventing copper diffusion into the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If copper metallization layer is used to increase electrical conductivity and reduce resistance, then power density is improved, but copper diffusion into the silicon carbide substrate occurs causing device degradation
Solution Approach 1:
A barrier layer structure comprising titanium and tungsten is introduced as an intermediary between the copper metallization layer and the silicon carbide substrate. This barrier layer prevents copper diffusion into the substrate while maintaining electrical conductivity, thus resolving the contradiction between achieving high power density with copper and preventing device degradation from copper diffusion.
Solution Approach 2:
The metallization structure uses a composite approach combining multiple materials: copper for high conductivity, titanium and tungsten for barrier properties, and nickel-silicon-aluminum for contact properties. This composite material system allows simultaneous achievement of high power density and device reliability by leveraging the complementary properties of each material layer.
2Power
If higher operational temperatures are used to improve power density, then power output increases, but thermal stress and premature aging occur
Solution Approach 1:
The invention changes the material parameters of the metallization system by using copper instead of traditional aluminum, and introduces a titanium-tungsten barrier layer with high thermal stability. These parameter changes enable the device to operate at higher temperatures with improved thermal robustness, allowing higher power density without premature aging from thermal stress.
3Area of stationary object
If lateral dimensions are reduced to decrease device footprint, then area is reduced, but thermal management becomes more difficult
Solution Approach 1:
The invention applies local quality optimization by using copper metallization with superior electrical and thermal conductivity in the critical interconnect regions. This localized improvement in material properties enhances heat dissipation efficiency in the reduced-footprint device, allowing smaller lateral dimensions without compromising thermal management.
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 allows for silicon carbide devices with increased power density and reduced footprint, improved heat dissipation, and enhanced robustness against thermal stress and short circuits, effectively addressing the limitations of existing silicon carbide devices.
Implementation Method 1
The silicon carbide device comprises a barrier layer structure comprising titanium and tungsten. The contact layer is located between the silicon carbide substrate and at least a part of the barrier layer structure.
Implementation Method 2
An ohmic connection is formed between the metallization layer and a doping region of the silicon carbide substrate via the barrier layer structure and the contact layer.
Data Source
AI summary
A power semiconductor device includes a semiconductor substrate having a wide bandgap semiconductor material and a first surface, an insulation layer above the first surface of the semiconductor substrate, the insulation layer including at least one opening extending through the insulation layer in a vertical direction, a front metallization above the insulation layer with the insulation layer being interposed between the front metallization and the first surface of the semiconductor substrate, and a metal connection arranged in the opening of the insulation layer and electrically conductively connecting the front metallization with the semiconductor substrate; wherein the front metallization includes at least one layer that is a metal or a metal alloy having a higher melting temperature than an intrinsic temperature of the wide bandgap semiconductor material of the semiconductor substrate.