SiC Trench Contact Layers for Low-Resistance Ohmic Interfaces
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Solution Overview
Problem
Existing silicon carbide (SiC) power devices face challenges in achieving low-resistance and high-reliability ohmic contacts between doped regions and external conductive structures, which are crucial for efficient power semiconductor performance, especially as devices trend towards smaller sizes.
Innovation Solution
A method involving the formation of trenches in a silicon carbide body with doped regions, where metallic interface layers, including transition metal silicides and refractory metal carbides, are formed on sidewalls and surfaces to create low-resistance ohmic contacts, eliminating the use of nickel to facilitate vertical patterning and improve contact area efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nickel is used in ohmic contact metallizations for n type SiC, then low-resistance ohmic contacts are achieved, but vertical patterning becomes difficult and manufacturing complexity increases
Solution Approach 1:
The patent removes nickel from the ohmic contact metallization stack, extracting the problematic element that prevented vertical patterning. This allows the manufacturing process to achieve vertical patterns without the interference of nickel, while maintaining low-resistance ohmic contacts through alternative material compositions such as cobalt, iron, or their alloys with aluminum or silicon.
Solution Approach 2:
The patent changes the material composition parameters of the ohmic contact metallization by substituting nickel with other metals such as cobalt, iron, or their alloys. This parameter change enables vertical patterning capability while maintaining or improving ohmic contact performance, resolving the contradiction between contact reliability and manufacturing ease.
2Productivity
If device size is reduced to save chip area, then productivity increases, but achieving low-resistance ohmic contacts becomes more difficult
Solution Approach 1:
The patent employs composite material structures in the ohmic contact metallization, such as alloys of cobalt or iron with aluminum or silicon. These composite materials provide both low-resistance electrical contact properties and compatibility with reduced device geometries, enabling scaled-down device sizes without sacrificing ohmic contact performance.
3Adaptability or versatility
If nickel aluminum (NiAl) alloys are used for both n type and p type SiC, then manufacturing versatility improves, but the inability to perform vertical patterning increases device complexity
Solution Approach 1:
The patent extracts nickel from the NiAl alloy system and replaces it with cobalt or iron-based materials. This removal eliminates the vertical patterning obstacle while preserving the ability to create ohmic contacts on both n-type and p-type SiC, thereby reducing device complexity without sacrificing manufacturing versatility.
Solution Approach 2:
The patent changes the base metal parameter in the alloy composition from nickel to cobalt or iron, which fundamentally alters the material's patterning behavior. This parameter change enables vertical patterning capability while maintaining the universal applicability to both n-type and p-type SiC contacts.
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 approach reduces electrical losses and enhances the efficiency of silicon carbide devices by providing low-resistance ohmic contacts, even in dense layouts, while allowing for flexible manufacturing processes on shared equipment with silicon wafers.
Implementation Method 1
A first interface layer in direct contact with the first doped region includes a first metal silicide/carbide containing a first transition metal. A first buffer layer is formed directly on the first interface layer. A second interface layer in direct contact with the second doped region includes a second metal silicide/carbide containing a second refractory metal.
Implementation Method 2
For achieving low resistive ohmic contacts between doped regions in a SiC body and conductive structures formed outside the SiC body, annealed nickel (Ni) has primarily been used in ohmic contact metallizations for n type SiC
Data Source
AI summary
A method of manufacturing a semiconductor device includes forming a trench that extends from a first surface into a silicon carbide body. A first doped region and an oppositely doped second doped region are formed in the silicon carbide body. A lower layer structure is formed on a lower sidewall portion of the trench. An upper layer stack is formed on an upper sidewall portion and/or on the first surface. The first doped region and the upper layer stack are in direct contact along the upper sidewall portion and/or on the first surface. The second doped region and the lower layer structure are in direct contact along the lower sidewall portion.