SiC Substrate Nitrogen Termination for Stable Gate Insulation
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Solution Overview
Problem
The conventional method of forming SiO2 insulating films on SiC substrates results in a rough interface, increased dangling bonds, and carbon diffusion into the insulating film due to hydrogen termination and subsequent oxidation, which affects the stability and mobility of semiconductor devices.
Innovation Solution
Replacing the outermost surface Si atoms of the SiC substrate with nitrogen, phosphorus, or arsenic to create a stable termination structure that reduces reactivity and prevents oxygen from entering the substrate, thereby maintaining a planar interface and suppressing carbon diffusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hydrogen termination is used on SiC substrate surface, then the surface can be easily activated for oxidation, but the interface becomes rough and carbon diffuses into the insulating film
Solution Approach 1:
The patent changes the chemical composition parameter of the surface termination from hydrogen to nitrogen. This parameter change fundamentally alters the surface chemistry, preventing oxygen penetration while maintaining surface activation capability. The nitrogen-terminated surface provides a stable interface that eliminates the roughening problem associated with hydrogen termination.
Solution Approach 2:
The patent replaces the unstable hydrogen termination (which has short lifetime and leads to interface degradation) with a stable nitrogen termination. The nitrogen-terminated surface maintains its protective function throughout the oxidation process, preventing carbon diffusion and interface roughening that would otherwise occur with hydrogen termination.
2Quantity of substance
If oxygen is allowed to enter the SiC substrate to form SiO2 film, then the insulating film can be formed, but the interface becomes rough and dangling bonds increase
Solution Approach 1:
The patent introduces nitrogen-terminated surface as an intermediary layer between the SiC substrate and the SiO2 insulating film. This intermediary nitrogen termination layer acts as a protective barrier that prevents direct oxygen attack on the SiC substrate, thereby preventing interface roughening and dangling bond formation while still allowing the necessary oxidation to form the insulating film.
Solution Approach 2:
The patent performs preliminary nitrogen termination of the SiC substrate surface before the oxidation process. This preliminary action creates a stable, oxygen-resistant surface layer that prevents the interface roughening and dangling bond problems that would otherwise occur during subsequent oxidation to form the SiO2 insulating film.
3Quantity of substance
If carbon atoms are discharged as CO during oxidation, then the insulating film forms, but carbon diffuses into the insulating film reducing device stability
Solution Approach 1:
The nitrogen-terminated surface acts as an intermediary barrier that controls the oxidation process. It allows necessary oxidation to form the insulating film while preventing excessive carbon discharge and diffusion into the film. This intermediary layer maintains device stability by regulating carbon atom behavior during the oxidation process.
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 enhances the stability and mobility of semiconductor devices by reducing interface roughness and carbon diffusion, improving electron mobility to 200 cm2/Vs or more, and maintaining a low carbon concentration in the insulating film.
Implementation Method 1
at an interface between the SiC substrate and the gate insulating film, some of elements of both of or one of Si and C in an outermost surface of the SiC substrate are replaced with at least one type of element selected from nitrogen, phosphorus, and arsenic
Data Source
AI summary
A semiconductor device of an embodiment at least includes: a SiC substrate; and a gate insulating film formed on the SiC substrate, wherein at an interface between the SiC substrate and the gate insulating film, some of elements of both of or one of Si and C in an outermost surface of the SiC substrate are replaced with at least one type of element selected from nitrogen, phosphorus, and arsenic.