SiC Semiconductor Ohmic Contact with Barrier Layer
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Solution Overview
Problem
The formation of ohmic contacts in semiconductor devices using silicon carbide (SiC) is challenging due to high contact resistance, requiring multiple steps and increasing manufacturing costs, and high-temperature heat treatment can degrade insulating properties of gate oxide films and interlayer insulating films.
Innovation Solution
A semiconductor device design with an SiC layer, an ohmic electrode, another electrode, and an insulating layer where the ohmic electrode is alloyed with Al, and the insulating layer is made of silicon nitride or silicon oxynitride to prevent reaction and maintain low electric resistance, and a barrier layer of tungsten, tantalum, or their oxides is used to further prevent reduction reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature heat treatment is performed to form ohmic contact between Ni and SiC, then contact resistance is lowered, but the insulating properties of gate oxide films and interlayer insulating films are degraded
Solution Approach 1:
The patent introduces a barrier layer as an intermediary substance between the Ni-based ohmic electrode and the insulating films (gate oxide film and interlayer insulating film). This barrier layer prevents direct contact and reaction between the electrode materials and insulating films during high-temperature heat treatment, thereby maintaining the insulating properties while allowing ohmic contact formation. The barrier layer acts as a protective mediator that resolves the conflict between achieving low contact resistance and preserving insulating characteristics.
Solution Approach 2:
The patent segments the electrode structure into multiple functional layers: the Ni-based ohmic electrode layer, the barrier layer, and the insulating films. This segmentation separates the functions of achieving low contact resistance (ohmic electrode) and maintaining insulating properties (barrier layer + insulating films), allowing each layer to perform its specific function without interfering with the other during high-temperature processing.
2Reliability
If different materials are used for electrodes in contact with n-type and p-type regions, then contact resistance is lowered, but the number of manufacturing steps increases
Solution Approach 1:
The patent employs a universal Ni-based ohmic electrode material that can form low-contact-resistance interfaces with both n-type SiC regions and p-type SiC regions. This multi-functional electrode material eliminates the need to switch between different electrode materials for different doping types, thereby reducing the number of manufacturing steps while maintaining low contact resistance for both n-type and p-type regions.
Solution Approach 2:
The patent utilizes the ability of Ni-based materials to form different interfacial compounds (such as NiSiC3 with n-type regions and Ni2SiC3 with p-type regions) through controlled heat treatment. By changing the heat treatment parameters, the same Ni-based electrode material can achieve optimal ohmic contact with both n-type and p-type regions, eliminating the need for material changes while maintaining low contact resistance.
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 design suppresses the deterioration of electric characteristics in insulating members, maintaining low contact resistance and improving integration and manufacturing efficiency by preventing reactions between the ohmic electrode and insulating layers at high temperatures.
Implementation Method 1
a rate of lowering in electric resistance in the insulating film is not higher than 5% when heating to a temperature not higher than 1200° C. is carried out while the ohmic electrode and the insulating layer are adjacent to each other
Implementation Method 2
by performing heat treatment as described above, Ni and Si atoms in SiC are alloyed. As a result of this alloying, Ni and SiC establish good ohmic contact
Implementation Method 3
heat treatment at a relatively high temperature (for example, approximately 1000° C.) has conventionally been used
Implementation Method 4
a barrier layer of tungsten, tantalum, or their oxides is used to further prevent reduction reactions
Data Source
AI summary
A semiconductor device having a construction capable of achieving suppressed deterioration of electric characteristics in an insulating member is provided. An n− SiC layer, a source contact electrode formed on a main surface of the n− SiC layer, a gate electrode arranged at a distance from the source contact electrode on the main surface of the n− SiC layer, and an interlayer insulating film located between the source contact electrode and the gate electrode are provided. A rate of lowering in electric resistance in the interlayer insulating film when heating to a temperature not higher than 1200 ° C. is carried out while the source contact electrode and the interlayer insulating film are adjacent to each other is not higher than 5%.