Nitride Semiconductor Substrate with SiN Barrier Against Al Diffusion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge is to prevent the diffusion of Al from the AlN layer to a single-crystal silicon substrate during the epitaxial growth of nitride semiconductor substrates, which can lead to the formation of low-resistance layers and cloudiness issues.
Innovation Solution
A method involving heat treatment of a single-crystal silicon substrate in a nitrogen atmosphere to form a silicon nitride film, followed by growing an AlN film and subsequently a GaN or AlGaN film, effectively suppressing Al diffusion and preventing cloudiness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an AlN buffer layer is laminated directly on a high-resistance single-crystal silicon substrate, then the substrate can be used for epitaxial growth, but Al diffuses to the substrate forming a low-resistance layer and channel
Solution Approach 1:
A silicon nitride film is introduced as an intermediate layer between the single-crystal silicon substrate and the AlN buffer layer. This intermediary layer acts as a diffusion barrier that prevents Al atoms from migrating into the silicon substrate, thereby maintaining the high-resistance property of the substrate while still allowing the AlN layer to function as a buffer for epitaxial growth.
Solution Approach 2:
The silicon nitride film is formed on the silicon substrate surface before the AlN buffer layer is deposited. This preliminary action creates a protective barrier in advance that prevents Al diffusion during subsequent epitaxial growth processes, eliminating the need for post-growth corrections.
2Ease of manufacture
If ammonia gas is used as a nitrogen source gas for forming SiN, then SiN can be formed, but cloudiness occurs on the epitaxial wafer
Solution Approach 1:
The nitrogen source gas is changed from ammonia (NH3) to nitrogen (N2). This parameter change in the chemical composition of the gas eliminates the cloudiness problem that occurs when ammonia is used, while still enabling the formation of the silicon nitride film through heat treatment.
3Productivity
If the AlN buffer layer is grown directly on the silicon substrate, then the growth process is shorter, but Al diffusion occurs extending the total epitaxial growth time
Solution Approach 1:
The silicon nitride film serves as a diffusion barrier that prevents Al atoms from the AlN buffer layer from migrating into the silicon substrate. This eliminates the need for extended growth times required to compensate for Al diffusion, maintaining efficient productivity while preventing quality degradation.
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 method successfully prevents Al diffusion to the high-resistance single-crystal silicon substrate, allowing for the manufacture of nitride semiconductor substrates with reduced Al concentration and clear epitaxial growth without cloudiness, suitable for high-frequency devices.
Implementation Method 1
subjecting a substrate for film formation made of single-crystal silicon to heat treatment under a nitrogen atmosphere to form a silicon nitride film on the substrate for film formation
Implementation Method 2
heat treatment under a nitrogen atmosphere to form a silicon nitride film
Implementation Method 3
growing an AlN film on the silicon nitride film
Implementation Method 4
growing a GaN film, an AlGaN film, or both on the AlN film
Implementation Method 5
diffusion of Al from the AlN layer to the single-crystal silicon substrate can be prevented
Data Source
AI summary
A method for manufacturing a nitride semiconductor substrate in which a nitride semiconductor is formed on a substrate for film formation includes: (1) subjecting a substrate for film formation made of single-crystal silicon to heat treatment under a nitrogen atmosphere to form a silicon nitride film on the substrate for film formation, (2) growing an AlN film on the silicon nitride film, and (3) growing a GaN film, an AlGaN film, or both on the AlN film. A method for manufacturing a nitride semiconductor substrate can prevent diffusion of Al to the high-resistance single-crystal silicon substrate when the AlN layer is epitaxially grown on the high-resistance single-crystal silicon substrate, and the GaN or the AlGaN layer is epitaxially grown on top of that.