LED Manufacturing Using Inverse Piezoelectric Substrate
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Solution Overview
Problem
Conventional blue LED elements with face-up or flip-chip structures using sapphire substrates face issues such as increased current density leading to heating, difficulty in chip production due to sapphire's hardness, and inefficient heat dissipation due to low thermal conductivity, and annealing treatments can degrade the p-type ohmic electrode.
Innovation Solution
A method for producing a light-emitting diode with an upper-lower electrode structure using a plating layer instead of a sapphire substrate, where a seed layer and plating layer are formed, and the substrate is removed, allowing for dry etching and formation of an n-type electrode without annealing, enhancing heat dissipation and preventing electrode degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If sapphire substrate is used with face-up or flip-chip structure, then the LED can be manufactured with conventional processes, but the current density increases in localized areas causing chip heating
Solution Approach 1:
The invention transitions from a planar face-up structure to a three-dimensional stacked structure by forming a semiconductor layer on an inverse piezoelectric actuator substrate. This vertical stacking allows current to flow through the thickness direction rather than laterally, distributing current density more uniformly and reducing localized heating while maintaining manufacturability.
Solution Approach 2:
The invention inverts the conventional structure by placing the semiconductor layer on the actuator substrate rather than on sapphire, and by forming electrodes on opposite surfaces (upper-lower electrode structure) rather than on the same surface. This inversion resolves the current density concentration problem while preserving ease of manufacture.
2Device complexity
If sapphire substrate is used, then the LED structure can be simplified, but high level technology is required to generate chips due to sapphire's extreme hardness and lack of cleavability
Solution Approach 1:
The invention extracts the semiconductor layer from the sapphire substrate using the inverse piezoelectric actuator's ability to release the layer through voltage application. This eliminates the need for difficult sapphire cleavage while maintaining a simplified overall structure, as the actuator substrate itself can be processed more easily than sapphire.
Solution Approach 2:
The invention changes the substrate material parameter from sapphire to an inverse piezoelectric actuator material that exhibits voltage-dependent mechanical properties. This allows the substrate to transition from a rigid, hard-to-process state to a more compliant state during chip generation, significantly easing manufacturing while maintaining structural simplicity.
3Ease of manufacture
If sapphire substrate is used, then the LED can be produced with conventional materials, but heat dissipation is inefficient due to sapphire's low thermal conductivity
Solution Approach 1:
The invention extracts the semiconductor layer from the sapphire substrate and transfers it to a new substrate that provides superior heat dissipation. This removes the thermal conductivity limitation while maintaining ease of manufacture, as the new substrate can be selected for optimal thermal properties.
Solution Approach 2:
The invention uses a composite structure combining the inverse piezoelectric actuator substrate with the semiconductor layer. The actuator substrate can be designed with high thermal conductivity materials to efficiently dissipate heat from the LED, while the overall structure maintains manufacturability through the actuator's unique properties.
4Reliability
If annealing treatment is performed to form ohmic junction, then the electrode layer can be formed on n-type semiconductor layer, but the p-type ohmic electrode degrades due to Ag migration resulting in reduced reflectance
Solution Approach 1:
The invention performs preliminary actions by forming the upper electrode and establishing the complete stacked structure before any heat treatment. The structure is designed so that critical electrodes are already in their final positions and configurations, minimizing the need for subsequent high-temperature annealing that would cause degradation.
Solution Approach 2:
The invention applies preliminary anti-action by designing the electrode structure and formation process to prevent Ag migration before it can occur. The upper-lower electrode configuration and the specific formation sequence prevent the degradation mechanism from activating, eliminating the need for annealing that would otherwise be required to form ohmic junctions.
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 enables efficient heat dissipation and prevents degradation of the ohmic electrode, maintaining the light extraction efficiency and current-voltage characteristics of the light-emitting diode.
Implementation Method 1
a semiconductor layer is formed on an inverse piezoelectric actuator substrate, and the semiconductor layer is released by application of voltage to the inverse piezoelectric actuator substrate
Data Source
AI summary
The present invention provides a method for producing a light-emitting diode, the method comprising a lamination step of forming a laminated semiconductor layer by sequentially laminating an n-type semiconductor layer, a light-emitting layer and a p-type semiconductor layer onto a substrate, as well as forming a plurality of reflective p-type electrodes on top of the p-type semiconductor layer, a plating step of forming a seed layer that covers the reflective p-type electrodes and the p-type semiconductor layer, and fowling a plating layer on top of the seed layer, a removal step of removing the substrate from the n-type semiconductor layer, thereby exposing a light extraction surface of the n-type semiconductor layer, and an electrode formation step of performing dry etching of the light extraction surface of the n-type semiconductor layer using an etching gas containing the same element as a dopant element within the n-type semiconductor layer, and subsequently forming an n-type electrode on the light extraction surface.