Nano-rugged Epitaxial Substrate for GaN Growth
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Solution Overview
Problem
The manufacturing of GaN-based microelectronic devices faces challenges due to high defect density caused by lattice mismatch between substrates and GaN layers, and existing epitaxial substrates with patterned surfaces require costly and time-consuming photolithography processes.
Innovation Solution
A nano-rugged and non-patterned epitaxial substrate is fabricated using a crystalline substrate with a poly-crystalline layer, where grain boundaries are etched to create a nano-rugged surface, allowing for low-cost and rapid production of high-quality epitaxial layers without the need for photolithography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a patterned surface is used to control epitaxial growth and reduce defect density, then the quality of epitaxial layer is improved, but the manufacturing cost and production time increase due to photolithography process
Solution Approach 1:
The invention changes the surface morphology parameter from macroscopic patterned structures to microscopic nano-rugged structures with specific Ra and Rz values. This parameter transformation allows the surface to provide epitaxial guidance through nanoscale features rather than micrometer-scale patterns, eliminating the need for photolithography while maintaining defect control
Solution Approach 2:
The invention transitions from two-dimensional planar patterns to three-dimensional nano-rugged surface structures. By creating vertical nanoscale protrusions and valleys on the substrate surface, the epitaxial guidance is achieved through dimensional transformation rather than lateral patterning, thus avoiding photolithography constraints
2Manufacturing precision
If a patterned surface is used to control epitaxial growth and reduce defect density, then the quality of epitaxial layer is improved, but the manufacturing cost increases due to photolithography process
Solution Approach 1:
The invention changes the surface morphology parameter from macroscopic patterned structures to microscopic nano-rugged structures with specific Ra and Rz values. This parameter transformation allows the surface to provide epitaxial guidance through nanoscale features rather than micrometer-scale patterns, eliminating the need for photolithography while maintaining defect control
Solution Approach 2:
The invention uses a simple poly-crystalline layer that can be easily deposited and removed, replacing the expensive and complex photolithography process. The poly-crystalline layer serves as a temporary structure to create nano-rugged features through low-cost wet etching, then is discarded after serving its purpose
3Manufacturing precision
If AlN buffer layer is used on SiC substrate to reduce threading dislocation density, then the defect density is reduced, but the manufacturing complexity and cost increase
Solution Approach 1:
The invention changes the critical parameter from material composition (AlN buffer layer) to surface morphology (nano-rugged structure). By transforming the substrate surface into nano-rugged structures, the epitaxial growth is controlled through surface geometry rather than material buffering, simplifying the manufacturing process while maintaining defect reduction
Solution Approach 2:
The invention extracts the essential function of the AlN buffer layer (defect control through surface modification) and separates it from the complex multi-layer buffer structure. By using only surface morphology modification without requiring specific buffer materials, the manufacturing complexity is reduced while retaining the defect control capability
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 results in a substrate that supports excellent quality epitaxial growth with reduced defect density, particularly threading dislocations, while reducing production costs and time, comparable to patterned substrates in terms of epitaxial layer quality.
Implementation Method 1
deposit a poly-crystalline layer of a material on the epitaxial surface
Implementation Method 2
deposit a poly-crystalline layer of a material on the epitaxial surface
Implementation Method 3
etch the grain boundaries of the poly-crystalline layer by a first wet etching process
Implementation Method 4
etch the regions within the grain boundaries of the ploy-crystalline layer by a plasma etching process
Implementation Method 5
remove the etched poly-crystalline layer by a second wet etching process
Implementation Method 6
a GaN semiconductor layer can be formed on the sapphire substrate with patterned surface in lateral epitaxial way to control dislocations
Data Source
AI summary
The invention provides an epitaxial substrate and fabrication thereof. The epitaxial substrate according to the invention includes a crystalline substrate. In particular, the crystalline substrate has an epitaxial surface which is nano-rugged and non-patterned. The epitaxial substrate according to the invention thereon benefits a compound semiconductor material in growth of epitaxy films with excellent quality. Moreover, the fabrication of the epitaxial substrate according to the invention has advantages of low cost and rapid production.