GaN Semiconductor Device Palladium Contact Oxidation
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Solution Overview
Problem
GaN-based semiconductor devices face challenges in achieving long-term stable operation due to difficulties in forming low-resistance p-type semiconductor layers and high contact resistance, with existing methods like heat treatment in oxygen atmospheres limiting metal electrode durability and causing degradation in device performance.
Innovation Solution
A method involving the formation of a gallium-nitride-based semiconductor structure with a p-type contact layer, selective removal of the contact layer to create a ridge or mesa structure, deposition of an insulation film, oxidation of the surface, and formation of a metal electrode using Pd and high-melting-point metals, followed by heat treatment in a non-oxygen gas atmosphere to prevent oxidation and promote alloying for low contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If heat treatment in oxygen atmosphere is performed to form metal electrode layer, then ohmic properties are improved, but metal electrode durability deteriorates due to oxidation
Solution Approach 1:
An oxide film is formed on the p-type GaN contact layer surface before metal electrode deposition. This preliminary oxidation creates a stable interface that enables ohmic contact without requiring subsequent heat treatment in oxygen atmosphere, thus preserving metal electrode durability while achieving good electrical contact properties.
Solution Approach 2:
Heat treatment is performed in an inert or reducing atmosphere (N2, H2, or forming gas) instead of oxygen atmosphere. This prevents oxidation of the metal electrode layer during heat treatment, maintaining metal durability while still achieving adequate ohmic properties through the pre-formed oxide film interface.
2Reliability
If HF solution is used to remove initial oxide film, then contact resistance is reduced, but insulation film is damaged
Solution Approach 1:
The harmful HF solution step is completely removed from the process. Instead of using HF to remove oxide films, the invention directly forms a controlled oxide film on the contact layer surface through oxidation, eliminating the need for any oxide removal step that could damage the insulation film.
Solution Approach 2:
A controlled oxide film serves as an intermediary layer between the p-type GaN contact layer and the metal electrode. This oxide film facilitates good electrical contact without requiring HF treatment, and its formation process is designed to not affect the insulation film on the ridge 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
This approach enables long-term stable operation at high current densities without degradation, allowing for the use of diverse high-melting-point metals like Ta, Cu, or W, and maintains electrical and optical confinement by avoiding wet processing that could reduce insulation film thickness.
Implementation Method 1
heat treatment using a gas other than oxygen... promote alloying for low contact resistance
Implementation Method 2
The step (d) is to form an oxide on a surface of either the ridge or the mesa
Data Source
AI summary
A method of manufacturing a semiconductor device provides a semiconductor device with a gallium-nitride-based semiconductor structure that allows long-term stable operation without degradation in device performance. After formation of an insulation film on a surface other than on a ridge surface, an oxygen-containing gas such as O2, O3, NO, N2O, or NO2 is supplied to oxidize a p-type GaN contact layer from the surface and to thereby form an oxide film on the surface of the p-type GaN contact layer. Then, a p-type electrode that establishes contact with the p-type GaN contact layer is formed by evaporation or sputtering on the oxide film and on the insulation film. Heat treatment is subsequently performed at temperatures between 400 and 700° C. in an atmosphere containing a nitrogen-containing gas such as N2 or NH3 or an inert gas such as Ar or He.