Textured Single Crystal via Selective Wet Etching
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Solution Overview
Problem
Existing methods for texturing single crystals, such as sapphire, for epitaxial growth of metal nitrides in LEDs are costly and complex, involving expensive techniques like photolithography and plasma etching, which are difficult to execute effectively.
Innovation Solution
A method involving depositing metal pads on the single crystal, followed by a protective layer, and using specific chemical etchants to selectively etch the metal pads and the crystal, creating cavities without substantially etching the crystal surface, thereby simplifying the texturing process and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography and plasma etching are used to texture single crystals, then the surface texture can be achieved, but the manufacturing cost increases and the process complexity increases
Solution Approach 1:
The patent uses a sacrificial organic layer (photoresist or spin-on-glass) that is deposited, patterned, and then completely removed after serving its purpose of defining the texture pattern. This disposable layer simplifies the overall process by eliminating the need for expensive photolithography equipment and complex plasma etching steps, while still achieving precise surface texturing through simple wet etching.
2Manufacturing precision
If photolithography and plasma etching are used to texture single crystals, then the surface texture can be achieved, but the manufacturing cost increases
Solution Approach 1:
The sacrificial organic layer is a low-cost material that can be deposited by simple spin-coating or dip-coating methods, replacing expensive photolithography processes. After pattern formation and wet etching, the layer is removed, having served its purpose at minimal cost.
Solution Approach 2:
The patent replaces complex plasma etching equipment and photolithography machinery with simple wet chemical etching processes. The organic sacrificial layer enables pattern transfer through conventional wet etching, eliminating the need for expensive vacuum plasma equipment and complex optical alignment systems.
3Manufacturing precision
If the protective layer is deposited on metal pads and single crystal, then selective etching can be achieved, but the adhesion between protective layer and metal may be poor
Solution Approach 1:
The organic sacrificial layer is deposited over the metal pads before etching, creating a protective mask that defines the texture pattern. This preliminary deposition ensures that the metal pads are protected during subsequent processing steps, and the layer's inherent adhesion to metal surfaces is sufficient for the brief processing time required.
Solution Approach 2:
The patent controls the thickness of the organic sacrificial layer to be sufficient for protection during etching but thin enough to allow complete removal afterward. By adjusting layer thickness parameters and etching time, the process achieves selective etching while maintaining adequate adhesion during the critical processing window.
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 allows for efficient texturing of single crystals with controlled cavity sizes, enhancing light extraction and reducing defect density in nitride deposition, improving LED performance while being more economical and straightforward to implement.
Implementation Method 1
etching the surface with a first compound that etches the metal more rapidly than the protective layer
Implementation Method 2
etching the surface with a second compound that etches the single crystal more rapidly than the protective layer
Implementation Method 3
etching the surface with a third compound that etches the protective layer more rapidly than the single crystal
Implementation Method 4
heat treating the thin metal layer so that it forms a textured metal mask
Data Source
AI summary
A method for fabricating a textured single crystal including depositing pads made of metal on a surface of a single crystal. A protective layer is deposited on the pads and on the single crystal between the pads; and etching the surface with a first compound that etches the metal more rapidly than the protective layer is carried out. Processing continues with etching the surface with a second compound that etches the single crystal more rapidly than the protective layer; and etching the surface with a third compound that etches the protective layer more rapidly than the single crystal. The textured substrate may be used for the epitaxial growth of GaN, AlN or III-N compounds (i.e. a nitride of a metal the positive ion of which carries a +3 positive charge) in the context of the fabrication of LEDs, electronic components or solar cells.