Microchip Surface Roughness for Fluidic Self-Alignment
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Solution Overview
Problem
The productivity of micro LED display apparatus manufacturing decreases as micro LED sizes shrink and display sizes increase, due to challenges in aligning micro-sized LED chips using existing transfer methods like laser lift off or pick and place.
Innovation Solution
A microchip design with a specific surface roughness profile, where the first surface has a lower roughness than the electrode layer, enhancing van der Waals forces for alignment in fluidic self-assembly methods, allowing for easier and more efficient alignment of microchips in a fluidic self-assembly method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If laser lift off or pick and place method is used to transfer micro LED, then micro LED can be transferred, but productivity is lowered as micro LED size becomes smaller and display size increases
Solution Approach 1:
The microchip structure enables self-alignment through differential adhesion forces. The first surface is designed with higher van der Waals force to the external contact surface compared to the electrode layer, causing the microchip to automatically orient itself during fluidic self-assembly without requiring complex external alignment mechanisms. This self-aligning capability dramatically improves productivity for large-area displays while maintaining precision even as micro LED size decreases.
2Measurement precision
If micro LED size becomes smaller, then display resolution is improved, but alignment difficulty increases and productivity decreases
Solution Approach 1:
The invention changes the surface roughness parameter of the microchip to optimize van der Waals forces. By controlling the surface roughness of the first surface to be less than 1 nm RMS and the electrode layer to be at least 2 nm RMS, the structure maintains strong adhesion for small micro LEDs while enabling automatic orientation through differential adhesion, thus improving both resolution and productivity simultaneously.
3Productivity
If fluidic self assembly method is used, then alignment efficiency is improved, but specific surface roughness control is required
Solution Approach 1:
The invention applies different surface roughness qualities to different parts of the microchip structure. The first surface is engineered with ultra-smooth finish (RMS < 1 nm) to maximize van der Waals adhesion to the external contact surface, while the electrode layer is designed with higher roughness (RMS ≥ 2 nm) to minimize adhesion and facilitate easy separation. This local differentiation of surface quality enables high alignment efficiency through fluidic self-assembly while providing clear fabrication targets for manufacturing control.
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 design significantly improves the alignment efficiency of microchips, increasing productivity by ensuring stable orientation and easy separation, leading to a higher ratio of aligned microchips in the desired direction, thus facilitating the manufacturing of large-area display apparatuses.
Implementation Method 1
a surface roughness of the first surface is smaller than a surface roughness of an upper surface of the electrode layer such that van der Waals force between the first surface and an external contact surface are greater than van der Waals force between the electrode layer and the external contact surface
Data Source
AI summary
Provided is a microchip including a chip body having a first surface and a second surface facing the first surface, and an electrode layer on the second surface, wherein a surface roughness of the first surface is smaller than a surface roughness of an upper surface of the electrode layer such that van der Waals force between the first surface and an external contact surface are greater than van der Waals force between the electrode layer and the external contact surface.