Selective Masking of III-N Crystal Facets for Free-Standing Layer Growth
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Solution Overview
Problem
Current methods for growing III-N layers with complex structures are limited by the inability to selectively mask specific crystal facets during epitaxial growth, restricting the formation of free-standing layers and devices with desired properties.
Innovation Solution
A process involving the selective deposition of a mask material on III-N layers with multiple facets, where growth rates are controlled to differentiate between lateral and vertical growth, allowing mask material to deposit on facets with lower growth rates, enabling selective masking and continued growth on other facets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the whole wafer is covered entirely by a mask during epitaxial growth, then dislocation density is reduced and strains are relaxed, but complex structures cannot be manufactured
Solution Approach 1:
The patent applies local quality by selectively masking only specific crystal facets (e.g., lateral facets) while leaving other facets (e.g., vertical facets) unmasked. This allows different regions of the wafer surface to have different properties: masked regions provide dislocation filtering and strain relaxation, while unmasked regions enable complex structure formation through selective epitaxial growth.
Solution Approach 2:
The masking approach segments the wafer surface into distinct zones based on crystal facet orientation. By treating different facets differently (masking some, leaving others exposed), the process enables simultaneous achievement of dislocation reduction in masked areas and complex structure fabrication in unmasked areas.
2Manufacturing precision
If external mask formation is performed outside the epitaxy reactor, then masking is achieved, but process complexity increases and alignment precision deteriorates
Solution Approach 1:
The patent merges the masking process with the epitaxial growth process by performing both operations within the same epitaxy reactor. The mask material is deposited during the epitaxial growth step itself, eliminating the need for separate external masking steps and subsequent alignment operations, thereby reducing process complexity and improving alignment precision.
Solution Approach 2:
The epitaxial growth process acts as an intermediary that simultaneously achieves both masking and structure formation. By using the epitaxial growth conditions to control mask material deposition selectively on specific facets, the process integrates multiple functions into a single step.
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 allows for the efficient formation of free-standing III-N layers and devices with improved properties by selectively masking specific facets during epitaxial growth, enabling the creation of complex structures and reducing dislocation density.
Implementation Method 1
carrying out epitaxial growth under growth conditions, by which (i) a growth of at least one further III-N layer selectively on a first type or a first group of facet(s) and (ii) a deposition of mask material selectively on a second type or a second group of facet(s) proceed simultaneously
Implementation Method 2
growth rates are controlled to differentiate between lateral and vertical growth, allowing mask material to deposit on facets with lower growth rates
Data Source
AI summary
In a process for forming a mask material on a III-N layer, wherein III denotes an element of the group III of the Periodic Table of Elements, selected from Al, Ga and In, a III-N layer having a surface is provided which comprises more than one facet. Mask material is selectively deposited only on one or multiple, but not on all facets. The deposition of mask material may be particularly carried out during epitaxial growth of a III-N layer under growth conditions, by which (i) growth of at least a further III-N layer selectively on a first type or a first group of facet(s) and (ii) a deposition of mask material selectively on a second type or a second group of facet(s) proceed simultaneously. By the process according to the invention, it is possible to produce free-standing thick III-N layers. Further, semiconductor devices or components having special structures and layers can be produced.