Molybdenum Schottky Contact for SiC Diode
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Solution Overview
Problem
Current silicon carbide (SiC) Schottky diodes do not fully realize their high performance potential for high-voltage, high-current capacity, and low-loss applications due to performance degrading defects in the SiC epilayer, particularly in high-voltage versions, and existing Schottky contact materials like titanium do not provide optimal forward current conduction and reverse voltage blocking capabilities.
Innovation Solution
A molybdenum Schottky contact is used, which offers improved forward current conduction and reverse voltage blocking performance, along with greater device stability at high temperatures, by forming a Schottky contact on an epitaxial SiC layer and annealing it at temperatures between 300 to 700°C, resulting in a Schottky barrier height of 1.2-1.3 eV and an ideality factor less than 1.1, reducing power loss in high-voltage SiC-SBDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If titanium Schottky contact is used, then device can be manufactured with standard materials, but forward current conduction and reverse voltage blocking performance are insufficient
Solution Approach 1:
The patent changes the material parameter from titanium to molybdenum, which has different physical and chemical properties including higher melting point and different work function. This material substitution optimizes the Schottky barrier characteristics, achieving superior forward current conduction and reverse voltage blocking performance while remaining manufacturable with standard semiconductor fabrication techniques
2Reliability
If higher annealing temperature is used, then Schottky contact performance improves, but device stability degrades due to material limitations
Solution Approach 1:
The patent changes the annealing temperature parameter to a higher range (600-700°C or above) which is enabled by using molybdenum instead of titanium. Molybdenum's higher melting point and thermal stability allow the device to withstand these elevated temperatures without degradation, thereby improving Schottky contact performance while maintaining device stability
Solution Approach 2:
The patent creates a composite structure with molybdenum Schottky contact on SiC epitaxial layer, where the molybdenum-titanium-nickel layered structure provides both high-temperature stability and optimal electrical characteristics. This composite approach allows higher annealing temperatures that improve contact performance while the stable SiC substrate maintains overall device integrity
3Loss of energy
If standard Schottky contact materials are used, then manufacturing process is simple, but power loss in high-voltage applications is high
Solution Approach 1:
The patent optimizes the Schottky barrier height parameter by selecting molybdenum as the contact material, which provides ideal energy band alignment with SiC. This reduces the barrier height to optimal levels, minimizing forward voltage drop and power loss in high-voltage applications while maintaining a relatively simple single-layer contact structure
4Temperature
If titanium Schottky contact is used, then device can operate at standard temperatures, but operating stability at high temperatures is poor
Solution Approach 1:
The patent changes the operating temperature parameter by using molybdenum Schottky contact which maintains stable electrical characteristics at elevated temperatures. Molybdenum's high melting point and thermal conductivity, combined with its compatible work function with SiC, enable the device to operate stably at high temperatures where titanium-based contacts would degrade
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 molybdenum Schottky contact enables SiC-SBDs to achieve superior blocking voltage of up to 1000V at room temperature, with better forward conduction and reverse voltage blocking characteristics compared to titanium-based diodes, while maintaining high-quality interface stability, thus reducing power loss and enhancing device performance.
Implementation Method 1
A molybdenum Schottky contact is disclosed that provides an improvement, as compared to titanium and other potential Schottky contact materials, in forward current conduction and reverse voltage blocking performance
Implementation Method 2
annealing the Schottky contact at a temperature in the range of 300 to 700° C.
Data Source
AI summary
A method for fabricating a diode is disclosed. In one embodiment, the method includes forming a Schottky contact on an epitaxial layer of silicon carbide (SiC) and annealing the Schottky contact at a temperature in the range of 300° C. to 700° C. The Schottky contact is formed of a layer of molybdenum.