Amorphous Carbon Gate Insulator for GaN HEMT Reliability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor devices with nitride semiconductor HEMTs face challenges in achieving high efficiency, low on-resistance, normally-off operations, and high withstand voltage, while maintaining high process yield and reliability, due to issues with gate insulating films such as aluminum oxide, which exhibit trap levels and voltage-dependent capacitance, affecting stable switching operations.
Innovation Solution
The use of amorphous carbon films, specifically a combination of nitrogen-doped and undoped amorphous carbon films, as gate insulating films, formed by filtered cathodic arc deposition, reduces membrane stress and peeling, providing stable switching operations and high reliability by minimizing trap levels and maintaining high film density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aluminum oxide is used as gate insulating film, then high withstand voltage is achieved, but trap levels and voltage-dependent capacitance occur affecting stable switching
Solution Approach 1:
The patent uses a composite insulating film structure consisting of a first insulating film (aluminum oxide) and a second insulating film (amorphous carbon). The aluminum oxide layer provides high withstand voltage, while the amorphous carbon layer reduces trap levels and eliminates voltage-dependent capacitance. This composite structure resolves the contradiction by combining materials with complementary properties.
Solution Approach 2:
The patent changes the material parameters of the insulating film by introducing amorphous carbon with specific properties (low trap level density, low voltage-dependent capacitance) to modify the overall film characteristics. This parameter change allows maintaining high withstand voltage while achieving stable switching operations.
2Reliability
If amorphous carbon films are used to reduce trap levels, then stable switching operations are achieved, but membrane stress and peeling issues occur
Solution Approach 1:
The composite structure of aluminum oxide and amorphous carbon films creates a system where each layer compensates for the weaknesses of the other. The aluminum oxide provides mechanical strength and adhesion, while the amorphous carbon provides electrical stability. This resolves the adhesion issue while maintaining the benefits of amorphous carbon.
Solution Approach 2:
The patent applies different materials to different locations/layers of the insulating film structure. The aluminum oxide layer is positioned to provide mechanical support and adhesion, while the amorphous carbon layer is positioned to provide electrical stability. This local differentiation of material properties resolves the contradiction between adhesion and electrical performance.
3Stress or pressure
If nitrogen-doped amorphous carbon films are used, then membrane stress is reduced, but film density may be affected
Solution Approach 1:
The patent combines nitrogen-doped amorphous carbon (for stress management) with undoped amorphous carbon or aluminum oxide (for density and electrical properties). This composite approach allows optimizing stress characteristics without sacrificing the density and electrical performance required for reliable operation.
Solution Approach 2:
The patent carefully controls the nitrogen doping concentration and film formation parameters to achieve the desired balance between stress reduction and density maintenance. By adjusting these parameters, the film properties are optimized to satisfy both requirements.
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 amorphous carbon films ensure stable switching operations and high reliability by reducing trap levels and maintaining high film density, achieving a threshold voltage change range of approximately 0 V and preventing film peeling, thus enhancing the semiconductor device's performance and manufacturing yield.
Implementation Method 1
formed by filtered cathodic arc deposition
Data Source
AI summary
A semiconductor device, includes a semiconductor layer formed above a substrate; an insulating film formed on the semiconductor layer; and an electrode formed on the insulating film. The insulating film has a membrane stress at a side of the semiconductor layer lower than a membrane stress at a side of the electrode.