LED Wafer Surface Roughening via Silver Particle Masking
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Solution Overview
Problem
Existing methods for roughening solid surfaces, such as those of light-emitting diodes (LEDs) and semiconductor substrates, are costly and time-consuming, particularly when using photolithography or blade machining, and fail to effectively reduce internal total reflection and create dislocation-free layers.
Innovation Solution
A particulate-mask surface-roughening method involving the formation of a masking film that coagulates into particulate form, allowing for etching of the work surface to create pits and projections, thereby reducing internal total reflection and facilitating epitaxial growth without the need for precise photomasks or expensive equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If photolithography is used to roughen the surface, then manufacturing precision can be achieved, but device complexity and cost increase significantly
Solution Approach 1:
The invention extracts and removes the complex photomask fabrication step from the surface roughening process. Instead of using photolithography with precisely patterned photomasks, the method directly deposits a masking film that is then coagulated into particles, eliminating the need for complex mask fabrication while achieving the desired surface roughness for reducing total internal reflection.
Solution Approach 2:
The invention replaces expensive, precisely fabricated photomasks with a simple masking film that is deposited and then coagulated into particles. This disposable-like approach uses inexpensive materials and processes (thermal deposition and heating) to achieve the same functional result, significantly reducing device complexity and cost.
2Device complexity
If blade machining is used to roughen the surface, then equipment simplicity is maintained, but manufacturing precision and surface quality deteriorate
Solution Approach 1:
The invention replaces the mechanical blade machining system with a thermal field-based system. Instead of using physical blades to mechanically remove material, the method uses thermal deposition to create a masking film followed by thermal coagulation to form particles, and then chemical etching to create the roughened surface. This substitution achieves superior surface precision while keeping the overall process simple.
Solution Approach 2:
The invention changes the fundamental parameters of the surface roughening process from mechanical removal to thermal-chemical formation. By controlling deposition thickness, coagulation temperature, and etching conditions, the method achieves precise control over surface unevenness in the order of tens or hundreds of nanometers, far exceeding blade machining capabilities.
3Productivity
If conventional etching methods are used, then etching speed is maintained, but surface uniformity and dislocation density increase
Solution Approach 1:
The invention applies local quality by creating non-uniform particle distribution through controlled coagulation. The masking film is coagulated into particles with varying sizes and densities across the surface, which then protect different regions during etching to create the desired roughened texture. This local variation in mask density achieves both surface uniformity and high etching speed.
Solution Approach 2:
The invention performs preliminary action by first depositing the masking film and then coagulating it into particles before the actual etching process. This preliminary structuring of the mask layer ensures uniform particle distribution and appropriate protective coverage across the entire surface, enabling subsequent high-speed etching to produce uniform roughened surfaces with reduced dislocation density.
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 significantly reduces the cost and time required for surface roughening, enhances LED efficiency by minimizing internal reflection, and enables the creation of dislocation-free semiconductor layers, resulting in improved light emission and crystal quality.
Implementation Method 1
a masking film of a material such as silver capable of thermal coagulation into particulate or granular form
Implementation Method 2
the work surface is roughened by etching with the prescribed etchant through the particulate mask
Data Source
AI summary
The method is disclosed as applied to roughening the light-emitting surface of an LED wafer for reduction of the internal total reflection of the light generated. A masking film of silver is first deposited on the surface of a wafer to be diced into LED chips. Then the masking film is heated to cause its coagulation into discrete particles. Then, using the silver particles as a mask, the wafer surface is dry etched to create pits therein. The deposition of silver on the wafer surface and its thermal coagulation into particles may be either successive or concurrent.