Low-Nitrogen Ohmic Contact Layer for Epitaxial Wafer Quality
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Solution Overview
Problem
The existing semiconductor epitaxial wafers for GaAs and InP integrated circuits face challenges with ohmic contact layers, including high stress, defects, and poor surface morphology due to lattice mismatch and high In content, which affects the quality of epitaxial growth and increases reactant generation during dry etching, leading to increased costs and reduced throughput.
Innovation Solution
A semiconductor epitaxial wafer design featuring an ohmic contact layer with low nitrogen content, such as GaAsN, GaAsNSb, or InGaAsN, which minimizes lattice mismatch and reduces defects, allowing for better epitaxial quality and reduced reactant generation during dry etching, while maintaining low contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If InGaAs or InGaAsSb is used in the ohmic contact layer to reduce contact resistance, then the ohmic contact performance is improved, but the lattice mismatch with GaAs substrate generates significant stress and defects
Solution Approach 1:
The patent changes the material parameters of the ohmic contact layer by using InGaAsN with controlled nitrogen content (0.001≤x≤0.05) and indium content (0.05≤y≤0.3), which adjusts the lattice constant and bandgap to achieve both low contact resistance and reduced lattice mismatch stress
Solution Approach 2:
The patent employs a composite material system InGaAsN that combines the advantages of InGaAs (low bandgap for good ohmic contact) with nitrogen incorporation (lattice matching capability), creating a material that simultaneously achieves excellent electrical contact and structural integrity
2Reliability
If the thickness of InGaAs layer exceeds critical thickness to achieve sufficient ohmic contact, then contact resistance is reduced, but defects and dislocations are generated in the layer
Solution Approach 1:
By incorporating nitrogen into the InGaAs layer to form InGaAsN, the patent changes the material's lattice constant, allowing the layer to maintain low contact resistance at reduced thickness without exceeding the critical thickness that would generate defects
3Reliability
If indium content is increased to reduce bandgap for better ohmic contact, then contact performance is improved, but more reactants are generated during dry etching affecting throughput and yield
Solution Approach 1:
The patent uses nitrogen incorporation to modify the material properties, achieving the required bandgap reduction for good ohmic contact with lower indium content (0.05≤y≤0.3), thereby reducing reactant generation during dry etching while maintaining electrical performance
4Reliability
If InGaAs(Sb) is used as ohmic contact layer to achieve low contact resistance, then ohmic contact is improved, but large lattice mismatch with GaAs substrate causes significant stress and poor surface morphology
Solution Approach 1:
The patent incorporates nitrogen into the InGaAs layer to form InGaAsN, which changes the lattice constant and allows better lattice matching with GaAs substrate, reducing misfit dislocation and improving surface morphology 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 use of low nitrogen content ohmic contact layers results in improved epitaxial quality, reduced defects, and lower reactant generation during dry etching, enhancing productivity and reducing costs by prolonging equipment maintenance cycles.
Implementation Method 1
the lattice mismatch between the ohmic contact layer and the substrate is controlled
Implementation Method 2
during the epitaxial growth process
Data Source
AI summary
Provided is a semiconductor epitaxial wafer, including a substrate, a first epitaxial structure, a first ohmic contact layer and a second epitaxial stack structure. It is characterized in that the ohmic contact layer includes a compound with low nitrogen content, and the ohmic contact layer does not induce significant stress during the crystal growth process. Accordingly, the second epitaxial stack structure formed on the ohmic contact layer can have good epitaxial quality, thereby providing a high-quality semiconductor epitaxial wafer for fabricating a GaAs integrated circuit or a InP integrated circuit. At the same time, the ohmic contact properties of ohmic contact layers are not affected, and the reactants generated during each dry etching process are reduced.