SiC Device Titanium Hydrogen Barrier
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Solution Overview
Problem
Conventional silicon carbide semiconductor devices face issues with high interface state density at the SiO2/SiC interface, leading to decreased channel mobility, increased ON resistance, and conduction loss, particularly due to the formation of defects during thermal oxidation of the gate insulating film.
Innovation Solution
A silicon carbide semiconductor device with a titanium film acting as a hydrogen absorber or blocker between the source electrode and the interlayer insulating film, preventing hydrogen ions from reaching the gate insulating film and reducing interface state density, thereby stabilizing the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thermal oxidation is used to form the gate insulating film on the silicon carbide semiconductor substrate, then the oxide film can be formed as a gate insulating film, but many defects (interface state) are formed near the junction interface of the gate insulating film and silicon carbide semiconductor portion, causing high interface state density
Solution Approach 1:
A titanium film is introduced as an intermediary layer between the aluminum source electrode and the interlayer insulating film. This titanium film acts as a hydrogen barrier, preventing hydrogen from the aluminum electrode from reaching the SiO2/SiC interface and causing interface states. The titanium film mediates the interaction between the electrode and the insulating film structure.
Solution Approach 2:
The invention converts the harmful effect of aluminum-hydrogen interaction into a beneficial hydrogen barrier function by using titanium. The aluminum source electrode naturally contains hydrogen, but by placing titanium between aluminum and the interlayer insulating film, the hydrogen is trapped in the titanium layer rather than reaching the sensitive SiO2/SiC interface, thus converting a potential harm into a protective function.
2Reliability
If hydrogen ions reach the gate insulating film during device operation, then positive charge is generated at the SiO2/SiC interface, but this causes threshold voltage variation and reduces device reliability
Solution Approach 1:
The titanium film serves as a hydrogen barrier intermediary that blocks hydrogen ions from reaching the gate insulating film and SiO2/SiC interface. This prevents the formation of positive charge at the interface, thereby maintaining stable threshold voltage and improving device reliability.
Solution Approach 2:
The titanium film is placed in advance between the aluminum source electrode and the interlayer insulating film to prevent hydrogen from reaching the gate insulating film. This preliminary protective action stops hydrogen-induced positive charge generation before it can occur, rather than attempting to correct the problem after it arises.
3Reliability
If a metal layer is added between the source electrode and interlayer insulating film to block hydrogen, then hydrogen-induced positive charge is prevented, but the device structure becomes more complex
Solution Approach 1:
The titanium film performs multiple functions simultaneously: it serves as a hydrogen barrier to prevent positive charge generation, acts as an adhesion layer between aluminum and the interlayer insulating film, and provides electrical connectivity. By combining multiple functions in a single layer, the structure complexity is minimized while achieving reliable hydrogen blocking.
Solution Approach 2:
The invention merges the hydrogen barrier function with the existing electrode structure by integrating the titanium film as part of the source electrode assembly. Rather than adding a separate complex hydrogen blocking system, the titanium layer is combined with the electrical connection function, simplifying the overall device structure.
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 effectively suppresses the variation of threshold voltage when negative voltage is applied, enhancing the reliability and stability of silicon carbide semiconductor devices by preventing hydrogen-induced positive charge generation and maintaining stable electrical characteristics.
Implementation Method 1
a first metal layer provided on a surface of the interlayer insulating film, the first metal layer absorbing or blocking hydrogen
Implementation Method 2
formation of an oxide film (SiO2 film) on a silicon carbide semiconductor substrate by thermal oxidation
Data Source
AI summary
A silicon carbide semiconductor device, including a silicon carbide semiconductor structure, an insulated gate structure including a gate insulating film contacting the silicon carbide semiconductor structure and a gate electrode formed on the gate insulating film, an interlayer insulating film covering the insulated gate structure, a metal layer provided on the interlayer insulating film for absorbing or blocking hydrogen, and a main electrode provided on the metal layer and electrically connected to the silicon carbide semiconductor structure.