GaN-on-SOI Substrate Edge Layout to Suppress Reaction Marks
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Solution Overview
Problem
The generation of reaction marks due to eutectic reactions between Si in the single crystal silicon substrate-on-insulative layer and Ga in trimethylgallium during GaN epitaxial growth leads to decreased device yield and contamination in the process, which existing methods fail to effectively prevent or control.
Innovation Solution
A nitride semiconductor substrate is created with a Ga-containing nitride semiconductor thin film formed on a single crystal silicon layer above a supporting substrate via an insulative layer, where the film is not formed inward from the edge of the single crystal silicon layer, and a method involving bonding, thinning, and growing AlN and GaN films is used to inhibit these reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If GaN is epitaxially grown on the single crystal silicon substrate-on-insulative layer, then the substrate provides electrical isolation and eliminates back-gate effects, but reaction marks are generated due to eutectic reactions between Si and Ga
Solution Approach 1:
An AlN layer is formed on the single crystal silicon layer before GaN epitaxial growth to prevent eutectic reactions between Si and Ga. This preliminary protective layer is deposited using atomic layer deposition (ALD) to ensure complete coverage, especially at the edges where reaction marks most commonly occur.
Solution Approach 2:
The patent applies different materials at different locations: AlN is specifically applied at the edge regions where reaction marks are most likely to form, while the central region can have different film structures. This localized approach targets the harmful reaction at critical areas without compromising the overall device performance.
2Object-generated harmful factors
If an AlN layer is formed on the single crystal silicon substrate to prevent reaction marks, then reaction mark generation is reduced, but reaction marks may still appear at several positions in the wafer substrate
Solution Approach 1:
The patent optimizes the AlN layer deposition parameters including thickness (typically 1-10 nm), deposition temperature, and atomic layer deposition cycle conditions to ensure complete coverage and effective reaction prevention. The thickness and deposition conditions are carefully controlled to achieve uniform protection across the entire wafer surface.
Solution Approach 2:
The AlN layer acts as an intermediary barrier between the Si substrate and Ga-containing precursors. This intermediate layer prevents direct contact and eutectic reaction while allowing the GaN epitaxial growth to proceed normally on top of it, effectively mediating the interaction between conflicting materials.
3Shape
If the edge of the single crystal silicon layer has a complex shape, then the substrate structure is formed, but the AlN layer is hardly formed at the edge and bare Si is present allowing Ga to react with Si
Solution Approach 1:
The AlN layer is deposited using atomic layer deposition before GaN epitaxial growth to ensure complete edge coverage. The ALD process is performed preliminarily to seal the complex edge geometry, preventing Ga from accessing bare Si at the edges where the complex shape creates vulnerability.
Solution Approach 2:
The patent replaces conventional deposition methods with atomic layer deposition (ALD) to achieve conformal coverage of the complex edge geometry. ALD's self-limiting surface reactions and conformal deposition capability substitute for mechanical coating methods that cannot adequately cover complex three-dimensional edge structures.
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 effectively inhibits the generation of reaction marks, resulting in improved device yield and precision by controlling the epitaxial growth and reducing contamination, while also eliminating back-gate effects and switching noise.
Implementation Method 1
a eutectic reaction product (hereinafter, 'reaction mark') between Si and Ga due to melt-back etching is likely to be generated
Implementation Method 2
A MOCVD method, which is one of methods for manufacturing a semiconductor thin film is commonly used because the method has excellent large-diameter formability and mass productivity and can form a uniform thin film crystal
Implementation Method 3
For a substrate for epitaxially growing GaN, etc. in the MOCVD method
Data Source
AI summary
A nitride semiconductor substrate, including a Ga-containing nitride semiconductor thin film formed on a substrate for film-forming in which a single crystal silicon layer is formed above a supporting substrate via an insulative layer, wherein the nitride semiconductor substrate has a region where the Ga-containing nitride semiconductor thin film is not formed inward from an edge of the single crystal silicon layer being a growth surface of the nitride semiconductor thin film. This provides: a nitride semiconductor substrate with inhibited generation of a reaction mark; and a manufacturing method therefor.