Silicon Carbide Ohmic Contact via Fluorine Termination
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Solution Overview
Problem
Conventional methods for forming ohmic electrodes on silicon carbide semiconductor devices require expensive ion implantation processes and can damage the substrate during roughening, leading to high contact resistance and poor mechanical properties, with termination effects being lost at high sintering temperatures.
Innovation Solution
A manufacturing method that terminates the surface and backside of the silicon carbide semiconductor substrate with an element having higher Pauling electronegativity than silicon, such as fluorine, using ion plasma processing, allowing for stable binding and reduced contact resistance without the need for ion implantation or substrate roughening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ion implantation process is used to form ohmic electrode, then contact resistance is reduced, but manufacturing cost increases and processing time increases
Solution Approach 1:
The patent extracts and eliminates the ion implantation process from the manufacturing flow, replacing it with a simpler surface treatment method using HF solution that achieves ohmic contact without requiring expensive ion implantation equipment and long processing times
Solution Approach 2:
The patent changes the surface treatment parameters by using chemical etching with HF solution instead of physical ion implantation, and by controlling the surface roughness within a specific range (Ra: 10-500 nm) to achieve optimal ohmic contact properties
2Reliability
If grinding process is used to form convexity and concavity on backside, then ohmic electrode can be formed, but substrate is damaged and cracks are generated
Solution Approach 1:
The patent introduces a chemical intermediary (HF solution) that selectively removes the damaged layer and terminates the surface with hydrogen atoms, providing a gentle alternative to mechanical grinding that achieves the same functional result without causing substrate damage
Solution Approach 2:
The patent replaces the mechanical grinding process with a chemical etching process using HF solution, substituting mechanical force with chemical reaction to achieve surface treatment without causing substrate damage or cracks
3Reliability
If hydrogen atom or hydroxyl group termination is used on backside, then ohmic property is improved, but termination effect is removed at high sintering temperature (≥800°C)
Solution Approach 1:
The patent changes the surface termination strategy by controlling the surface roughness parameters (Ra: 10-500 nm) and using specific HF treatment conditions to create a hydrogen-terminated surface that maintains its ohmic properties through high-temperature sintering processes
Solution Approach 2:
The patent performs preliminary surface treatment with HF solution before electrode formation to establish a stable hydrogen-terminated surface with appropriate roughness, which prepares the surface to maintain its termination effect through subsequent high-temperature processing
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 method achieves excellent ohmic properties and maintains termination effects at high annealing temperatures, reducing contact resistance and preventing substrate damage, while eliminating the need for costly ion implantation and substrate roughening processes.
Implementation Method 1
terminating the surface and backside of the silicon carbide semiconductor substrate with an element having higher Pauling electronegativity than silicon, such as fluorine, using ion plasma processing
Data Source
AI summary
A silicon carbide semiconductor device includes: a semiconductor substrate made of silicon carbide single crystal and having a principal surface and a backside; and an ohmic electrode contacting one of the principal surface and the backside of the semiconductor substrate in an ohmic manner. A boundary between the ohmic electrode and the one of the principal surface and the backside of the semiconductor substrate is terminated with an element, which has a Pauling electronegativity larger than silicon and a binding energy with silicon larger than a binding energy of Si—H.