Micro-LED Masked Epitaxy Without Plasma Mesa Etching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for manufacturing micro-LEDs face challenges such as low efficiency, plasma damage during dry etching, and high costs due to laser lift-off and transfer printing, particularly in achieving high-quality micro-LEDs with small lateral dimensions.
Innovation Solution
A method involving the formation of micro-LEDs using III-nitride semiconductor material, where a dielectric mask layer is used to control the size and shape of the exposed region for growing the LED structure, avoiding dry etching and allowing for precise control of the LED's lateral dimensions, and incorporating a porous region to enhance optical properties through electrochemical porosification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If dry etching is used to define micro-scale LED mesas, then the LED structure can be precisely defined, but plasma damage to the side wall occurs which influences emission efficiency and lifetime
Solution Approach 1:
The patent extracts the harmful plasma damage effect from the etching process by replacing dry etching with a wet chemical etching process. This allows precise mesa definition to be achieved through controlled chemical etching of the sacrificial layer, eliminating the plasma damage that would otherwise harm the LED structure's reliability and emission efficiency.
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary element that enables precise mesa formation without directly etching the LED structure. The sacrificial layer is selectively removed through wet chemical etching, creating well-defined mesas while the LED layers remain protected from damage. This intermediary approach allows precision manufacturing without the harmful side effects of plasma etching.
2Adaptability or versatility
If normal LED epitaxy is used to generate all three main colours (RGB) on the same chip, then device integration is achieved, but efficiencies are low for green and red micro-LEDs
Solution Approach 1:
The patent applies local quality by using compositionally graded InGaN layers with varying indium content in different regions of the same chip. By controlling the indium concentration locally, different emission wavelengths (colors) are achieved across the chip, with optimized efficiency for each color region rather than uniform low efficiency across all colors.
Solution Approach 2:
The patent changes the compositional parameter of the InGaN alloy (indium content) to tune the emission wavelength and efficiency. By adjusting the indium concentration from 5-30%, the patent achieves different colors (blue, green, red) with optimized efficiency for each, resolving the efficiency problem while maintaining multi-color capability on the same chip.
3Ease of manufacture
If laser lift-off is used for transfer, then micro-LEDs can be transferred to substrates, but the process is low yield and costly
Solution Approach 1:
The patent uses a disposable sacrificial layer made from common semiconductor materials that can be easily and cheaply removed by wet chemical etching. This replaces the expensive and low-yield laser lift-off process with a simple, low-cost chemical etching process that achieves high-yield transfer of micro-LEDs to substrates, dramatically improving productivity and reducing manufacturing costs.
4Ease of manufacture
If transfer printing is used with pre-existing strain/bow issues, then micro-LEDs can be transferred, but yield is low due to defects
Solution Approach 1:
The patent performs preliminary action by forming the complete LED structure on a sacrificial layer before transfer. The sacrificial layer is designed to be perfectly flat and strain-free, providing an ideal foundation for LED growth. This preliminary preparation eliminates pre-existing strain and bow issues that would otherwise cause defects and reduce yield during transfer printing.
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 results in more reliable and brighter micro-LEDs with reduced plasma damage, enabling the production of high-quality micro-LEDs with improved efficiency and reduced manufacturing costs.
Implementation Method 1
The porous region of III-nitride material may be formed by porosifying a layer of III-nitride material, or alternatively the porous region may be formed by porosifying a layer of III-nitride material on a substrate
Data Source
Figure 1~3
Figure 4~7
Figure 8~10
AI summary
A method of manufacturing a micro-LED comprises the steps of forming an n-doped connecting layer of III-nitride material over a porous region of III-nitride material, and forming an electrically-insulating mask layer on the n-doped connecting layer. The method comprises the steps of removing a portion of the mask to expose an exposed region of the n-doped connecting layer, and forming an LED structure on the exposed region of the n-doped connecting layer. A method of manufacturing an array of micro-LEDs comprises the step of removing a portion of the mask to expose an array of exposed regions of the n-doped connecting layer, and forming an LED structure on each exposed region of the n-doped connecting layer. A micro-LED and array of micro-LEDs are also provided.