Aluminum Nitride Substrate Passivation for Epitaxial Growth
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Solution Overview
Problem
Aluminum nitride substrates are prone to surface oxidation, which hinders their long-term storage and usage in thin film growth due to the formation of reactive oxide-hydroxide layers, making it difficult to maintain optimal conditions for epitaxial growth.
Innovation Solution
A method involving a wet chemical etch to form a passivating aluminum hydroxide layer on the substrate surface, which can be easily removed, using acids or bases, followed by thermal annealing in the presence of reactive nitrogen to shift the oxygen bonding state towards the hydroxyl state, thereby protecting the substrate and ensuring optimal conditions for film growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If aluminum nitride substrates are stored for long periods, then the substrate availability increases, but surface oxidation occurs forming reactive oxide-hydroxide layers that deteriorate the surface condition for epitaxial growth
Solution Approach 1:
A passivation layer is introduced as an intermediary protective barrier between the aluminum nitride substrate surface and the oxidizing atmosphere. This layer prevents direct contact between atmospheric oxygen and the substrate surface, thereby preventing oxidation while allowing the substrate to be stored for extended periods. The passivation layer can be easily removed prior to epitaxial growth to restore the surface to an optimal state.
Solution Approach 2:
The substrate surface is treated to create a chemically inert passivation layer that resists reaction with atmospheric oxygen and moisture. This inert layer protects the reactive aluminum nitride surface from oxidation during storage, enabling long-term preservation without degradation of the surface condition needed for subsequent epitaxial growth.
2Manufacturing precision
If surface preparation is performed to optimize film growth conditions, then the quality of epitaxial film increases, but the substrate becomes more susceptible to oxidation and requires protective passivation
Solution Approach 1:
Surface preparation treatments are performed in advance to optimize the substrate surface for epitaxial growth, creating the desired surface morphology and chemical state. Immediately following this preparation, a passivation layer is applied to protect the freshly prepared surface from oxidation during storage and handling, thereby preserving the high-quality surface condition until the epitaxial growth process is performed.
Solution Approach 2:
The passivation layer serves as a temporary intermediary protective coating applied after surface preparation. It preserves the optimized surface conditions without interfering with the subsequent epitaxial growth process, as it can be easily removed when needed to expose the prepared surface for film deposition.
3Reliability
If a protective passivation layer is formed on the substrate surface, then oxidation resistance improves, but the layer must be easily removable to restore optimal growth conditions
Solution Approach 1:
The passivation layer is designed with specific chemical and physical parameters that enable easy removal. By controlling the composition, thickness, and bonding characteristics of the passivation layer, it provides adequate protection against oxidation during storage while allowing for simple and efficient removal through mild chemical or thermal treatments prior to epitaxial growth, without requiring complex or aggressive removal processes.
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 method effectively reduces surface reactivity, maintains the substrate in an optimal state for film growth, and allows for easy removal of the passivating layer, ensuring consistent and desirable properties, thus extending the substrate's usability and improving film deposition quality.
Implementation Method 1
forming a passivating layer on at least a portion of the substrate surface by applying a wet chemical etch to the substrate surface. The passivating layer can particularly comprise an aluminum hydroxide layer.
Implementation Method 2
followed by thermal annealing in the presence of reactive nitrogen to shift the oxygen bonding state towards the hydroxyl state
Data Source
AI summary
The present invention provides methods of protecting a surface of an aluminum nitride substrate. The substrate with the protected surface can be stored for a period of time and easily activated to be in a condition ready for thin film growth or other processing. In certain embodiments, the method of protecting the substrate surface comprises forming a passivating layer on at least a portion of the substrate surface by performing a wet etch, which can comprise the use of one or more organic compounds and one or more acids. The invention also provides aluminum nitride substrates having passivated surfaces.