Micro LED Insulating Layer Layout for Clean Laser Lift-Off
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Solution Overview
Problem
The epitaxial insulating layer often remains on the peripheral surface of lifted-off micro LEDs during the manufacturing process, affecting the post-transfer process and light emitting efficiency.
Innovation Solution
A micro LED structure with a thicker first insulating layer covering the mesa surface and a thinner second insulating layer directly covering the second side surface, where the thickness ratio of the first to the second insulating layer is between 10 and 50, preventing the epitaxial insulating layer from remaining on the peripheral surface and improving light emitting efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single insulating layer with thickness from 0.5 μm to 1 μm is formed on the micro LED structure, then electrical passivation is achieved, but the insulating layer extends to the substrate surface and remains on the peripheral surface after laser lift-off, adversely affecting post-transfer process
Solution Approach 1:
The patent divides the single insulating layer into two distinct layers: a first insulating layer (thickness from 0.5 μm to 1 μm) for electrical passivation of the micro LED structure, and a second insulating layer (thickness from 50 nm to 200 nm) for covering the peripheral surface. This segmentation allows each layer to serve its specific function without interfering with the laser lift-off process, resolving the contradiction between electrical passivation and post-transfer manufacturability.
Solution Approach 2:
The patent applies different thicknesses and positions to different insulating layers based on local requirements. The first insulating layer is thicker and covers the micro LED structure body for electrical passivation, while the second insulating layer is thinner and specifically covers the peripheral surface exposed by the mesa structure. This local differentiation ensures that the peripheral surface is properly covered without extending to the substrate, enabling successful laser lift-off while maintaining electrical passivation.
2Ease of manufacture
If the insulating layer thickness is reduced to prevent remaining on peripheral surface, then post-transfer process is improved, but light emitting efficiency may be adversely affected
Solution Approach 1:
By segmenting the insulating coverage into two layers with different thicknesses and functions, the patent maintains adequate light emitting efficiency through the first insulating layer (0.5-1 μm) while using a thinner second insulating layer (50-200 nm) specifically for peripheral surface coverage. This segmentation allows the peripheral surface to be covered sufficiently for laser lift-off without requiring excessive thickness that would harm light emitting efficiency.
Solution Approach 2:
The patent applies different insulating layer thicknesses to different regions based on local functional requirements. The first insulating layer provides sufficient thickness for electrical passivation and light management on the micro LED structure body, while the second insulating layer provides just enough coverage on the peripheral surface to prevent contamination during transfer, without excessive thickness that would reduce light emitting efficiency.
3Reliability
If the first insulating layer extends to cover the peripheral surface, then electrical passivation is improved, but the epitaxial insulating layer remains on the peripheral surface after laser lift-off
Solution Approach 1:
The patent segments the peripheral surface coverage function between two layers: the first insulating layer covers the micro LED structure body for electrical passivation, while the second insulating layer specifically covers the peripheral surface exposed by the mesa structure. This segmentation ensures that the first insulating layer does not extend to the substrate surface, preventing residual insulating layer formation after laser lift-off while maintaining proper electrical passivation.
Solution Approach 2:
The patent applies different coverage characteristics to different regions: the first insulating layer provides comprehensive coverage on the micro LED structure body for electrical passivation, while the second insulating layer provides targeted coverage on the peripheral surface. This local differentiation ensures precise control over which surfaces are covered and to what extent, preventing the epitaxial insulating layer from remaining on the peripheral surface after transfer.
Data Source
AI summary
A micro light emitting diode structure including an epitaxial structure, a first insulating layer and a second insulating layer is provided. The epitaxial structure includes a first type semiconductor layer, a light emitting layer and a second type semiconductor layer. The first type semiconductor layer, the light emitting layer and a first portion of the second type semiconductor layer form a mesa. A second portion of the second type semiconductor layer is recessed relative the mesa to form a mesa surface. The first insulating layer covers from a top surface of the mesa to the mesa surface along a first side surface of the mesa, and exposes the second side surface. The second insulating layer directly covers a second side surface of the second portion, wherein a thickness ratio of the first insulating layer to the second insulating layer is between 10 and 50.