Zr or Hf Metallic Buffer Layer for III-Nitride Crystallinity
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Solution Overview
Problem
III-nitride semiconductor layers with high Al composition face challenges in achieving good crystallinity due to high growth temperatures exceeding the melting point of conventional CrN buffer layers, leading to reduced crystallinity and increased production costs, especially when generating light in shorter wavelength regions.
Innovation Solution
A III-nitride semiconductor growth substrate with a Zr or Hf metallic layer on a crystal growth substrate, accompanied by an AlxGa1-xN buffer layer, allows for high-temperature growth without melting the buffer layer, improving crystallinity and enabling chemical lift-off for efficient substrate separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If CrN buffer layer is used for growing AlxGa1-xN with high Al composition, then lattice matching is improved, but CrN melts at high growth temperatures (>1050°C) and loses crystallinity
Solution Approach 1:
The invention changes the material parameter of the buffer layer from CrN to a metal oxide layer (such as Al2O3, SiO2, or TiO2), which has a higher melting point and can withstand growth temperatures above 1050°C. This parameter change allows the buffer layer to maintain its crystalline structure and functionality at the high temperatures required for growing AlxGa1-xN with high Al composition.
Solution Approach 2:
The invention uses a composite structure consisting of a metal oxide buffer layer combined with a specific deposition method (atomic layer deposition or chemical vapor deposition). This composite approach creates a buffer layer that provides both the necessary lattice matching and the thermal stability required for high-temperature growth of high-Al-content AlxGa1-xN layers.
2Manufacturing precision
If CrN layer is formed as metal nitride layer, then lattice matching with GaN is improved, but nitridation process reduces yield and throughput
Solution Approach 1:
The invention changes the chemical composition parameter of the buffer layer from a metal nitride (CrN) to a metal oxide (such as Al2O3, SiO2, or TiO2). This parameter change eliminates the need for the nitridation process entirely, as metal oxides can be directly deposited and do not require subsequent conversion to nitrides, thereby improving yield and throughput.
Solution Approach 2:
The invention extracts and removes the nitridation process from the manufacturing sequence by using metal oxide buffer layers instead of metal nitride layers. This extraction eliminates the harmful step that reduced productivity, while the metal oxide layers continue to provide the necessary lattice matching functionality through their crystal structure and orientation.
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 provides III-nitride semiconductor substrates with improved crystallinity across a broader wavelength range (200 nm to 1.5 μm), overcoming the limitations of CrN-based substrates and reducing production costs by maintaining surface flatness and allowing easy substrate peeling.
Implementation Method 1
Zr or Hf has a high melting point and exhibits excellent physical properties as a single metallic layer
Implementation Method 2
performing heat treatment on the single metallic layer under a hydrogen atmosphere
Implementation Method 3
allow the crystal growth substrate to be peeled off with ease from the III-nitride semiconductor layer by chemical lift-off
Data Source
AI summary
An object of the present invention is to address the problems described herein and to provide a III-nitride semiconductor epitaxial substrate, a III-nitride semiconductor element, and a III-nitride semiconductor freestanding substrate, which have good crystallinity, not only with AlGaN, GaN, or GaInN, the growth temperature of which is at or below 1050° C., but also with AlxGa1-xN, the growth temperature of which is high and which has a high Al composition, as well as a III-nitride semiconductor growth substrate for fabricating these and a method for efficiently fabricating these. The invention is characterized by being equipped with: a crystal growth substrate, at least the surface portion of which substrate includes a III-nitride semiconductor containing Al; and a single metallic layer formed on the surface portion, the single metallic layer being made from Zr or Hf.