Micro LED DBR Structure With Inclined Through-Holes for Electrode Coverage
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Solution Overview
Problem
The existing micro light-emitting diode (LED) chips face issues with low light-emitting efficiency due to poor step coverage of the Distributed Bragg Reflector (DBR) reflective layer, leading to limited light reflection, electrode coverage problems, and a risk of metal fracture, which affects the reliability of the LED chips.
Innovation Solution
A micro light-emitting element is designed with a substrate and LED array units that include an epitaxial laminated layer, an electrode extension bar, a DBR structure layer, and electrodes, where the DBR structure layer consists of a DBR adhesive layer, a DBR reflective layer, and a DBR sacrificial layer, with through holes to improve light reflection and electrode coverage, and the DBR sacrificial layer is etched to form an inverted trapezoidal through hole with an inclined side wall to reduce height differences and enhance electrode reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional high-temperature vapor deposition is used to fabricate the DBR reflective layer, then the DBR structure can be formed, but the film thickness is non-uniform on the non-planar surface resulting in poor step coverage and limited light reflection
Solution Approach 1:
The patent introduces a planarization layer between the substrate and the DBR reflective layer to pre-level the non-planar surface before depositing the reflective layer. This preliminary planarization action ensures uniform film thickness and poor step coverage is eliminated, allowing the DBR structure to achieve its full light reflection potential
Solution Approach 2:
The planarization layer acts as an intermediary element that mediates between the non-planar substrate surface and the DBR reflective layer. It provides a planar interface for uniform deposition while maintaining the underlying non-planar structure, thus resolving the conflict between surface topology and film uniformity
2Ease of manufacture
If electrode extension bars are used to support the electrodes, then the electrodes can be covered, but significant height difference is created between the DBR reflective layer above the electrode extension bars and that above the ITO leading to stress concentration and risk of electrode detachment
Solution Approach 1:
The planarization layer is deposited in advance to compensate for the height difference caused by electrode extension bars. By performing this planarization action before electrode deposition, the surface becomes level, eliminating stress concentration points and preventing electrode detachment while maintaining proper electrode coverage
3Manufacturing precision
If ICP dry etching is used to etch the DBR layer to form through-holes for carrying the electrodes, then the through-holes can be formed, but the anisotropic etching creates steep etching angles that are not conducive to subsequent electrode coverage and easily lead to metal fracture
Solution Approach 1:
The patent changes the etching parameters by switching from ICP dry etching to wet etching. This parameter change transforms the etching mechanism from anisotropic to isotropic, producing gentler etching angles that facilitate subsequent electrode coverage while maintaining precise through-hole formation
Solution Approach 2:
The patent replaces the mechanical/physical ICP dry etching process with a chemical wet etching process. This substitution changes the etching mechanism from plasma-based physical removal to chemistry-based removal, resulting in different etching profiles that are more favorable for electrode deposition
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 solution improves light reflection efficiency, ensures reliable electrode coverage, and reduces the risk of electrode detachment, thereby enhancing the overall reliability and performance of the micro light-emitting element.
Implementation Method 1
the light emitted from the active layer needs to be reflected by a high-quality mirror of the DBR to improve light output
Implementation Method 2
when the DBR layer is etched with Inductively Coupled Plasma (ICP) dry etching to form through-holes
Implementation Method 3
the DBR reflective layer is a TI3O5/SiO2 multilayer optical design structure fabricated using high-temperature vapor deposition
Data Source
AI summary
The present disclosure provides a micro light-emitting element, method for manufacturing a micro light-emitting element, and a light-emitting device. The micro light-emitting element includes a DBR structure layer, including a DBR adhesive layer, a DBR reflective layer, and a DBR sacrificial layer, where the DBR adhesive layer, the DBR reflective layer, and the DBR sacrificial layer are sequentially stacked. Subsequent structural coverage of a DBR reflective layer is improved by means of the DBR adhesion layer. Density of film layers of the DBR sacrificial layer, the DBR reflective layer, and the DBR adhesive layer are sequentially increased, so that etching rates of the DBR sacrificial layer, the DBR reflective layer, and the DBR adhesive layer are sequentially decreased during etching, thereby forming an inverted trapezoidal through hole which comprises an inclined side wall by an etching process.