Single Alloy Conductor for Simultaneous Ohmic Contacts to SiC
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Solution Overview
Problem
Conventional ohmic contact metallization for semiconductor devices fails at high temperatures due to instability and complexity, requiring multiple process steps and high-energy ion implantation, which is costly and damaging to the lattice structure, limiting their operation to below 600°C.
Innovation Solution
A single alloy conductor, such as a Pt:Ti composition, is used to form simultaneous ohmic contacts to both n- and p-type silicon carbide (SiC) surfaces, acting as a diffusion barrier against gold and oxygen, and enabling reliable operation at temperatures exceeding 600°C, thereby reducing fabrication complexity and cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ohmic contact metallization is used, then devices can be fabricated with traditional processes, but the contact metallization becomes unstable and fails at high temperatures above 600°C
Solution Approach 1:
The patent changes the material parameters by using a tungsten-based alloy composition (W70-Ni30) instead of conventional metals. This compositional parameter change enables the contact metallization to maintain stability and ohmic characteristics at high temperatures above 600°C, resolving the reliability-temperature contradiction
Solution Approach 2:
The patent employs a composite alloy material consisting of tungsten and nickel in specific proportions (W70-Ni30). This composite material combines the high-temperature stability of tungsten with the beneficial electrical properties of nickel, creating a contact metallization that remains reliable at temperatures where conventional single metals would fail
2Reliability
If multiple process steps including ion implantation are used to form ohmic contacts on both n- and p-type layers, then exclusive ohmic contact can be achieved, but the fabrication complexity and cost increase significantly
Solution Approach 1:
The tungsten-based alloy contact metallization performs multiple functions simultaneously: it forms ohmic contacts on both n-type and p-type SiC layers without requiring separate metallization schemes. This universal contact material eliminates the need for multiple deposition, photolithography, and etching steps that would otherwise be required to create different contacts for different doping types, thereby reducing fabrication complexity while maintaining reliable ohmic contact performance
Solution Approach 2:
The patent merges the requirements for n-type and p-type ohmic contacts into a single metallization layer. Instead of fabricating separate contact structures for each doping type through multiple process steps, the W70-Ni30 alloy is deposited as one unified layer that provides ohmic contact to both polarities, simplifying the overall fabrication process
3Reliability
If high-energy ion implantation is used to create degenerately doped layers, then ohmic contact to both n- and p-type layers becomes possible, but lattice structure damage occurs and additional activation annealing at 1200°C is required
Solution Approach 1:
The patent extracts the high-energy ion implantation step from the fabrication process entirely. By using the W70-Ni30 alloy contact metallization, the invention achieves ohmic contact formation without requiring the harmful ion implantation process that causes lattice damage and necessitates high-temperature activation annealing, thereby eliminating this harmful factor while maintaining contact reliability
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 the simultaneous formation of ohmic contacts on both n- and p-type SiC surfaces in a single process step, enhancing the reliability and stability of semiconductor devices at high temperatures, reducing production costs and time, and eliminating the need for high-energy ion implantation.
Implementation Method 1
A single alloy conductor, such as a Pt:Ti composition, is used to form simultaneous ohmic contacts to both n- and p-type silicon carbide (SiC) surfaces
Implementation Method 2
acting as a diffusion barrier against gold and oxygen
Data Source
AI summary
Use of a single alloy conductor to form simultaneous ohmic contacts (SOC) to n- and p-type 4H—SiC. The single alloy conductor also is an effective diffusion barrier against gold (AU) and oxygen (O2) at high temperatures (e.g., up to 800° C.). The innovation may also provide an effective interconnecting metallization in a multi-level metallization device scheme.