MicroLED Dry Surface Etching for Mesa Defect Removal
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Solution Overview
Problem
The mesa etch process in microLED structure formation induces crystallographic defects, leading to reduced light output and efficiency, and existing wet etch methods are difficult to control, causing shape alterations and uniformity issues.
Innovation Solution
A dry etch process using alternating cycles of chlorine and argon gases in an inductively coupled plasma or reactive thermal process to selectively remove the defective surface layers, preserving the geometry and smoothness of the microLED structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a mesa etch process is performed to form microLED structures, then the structures are formed with defined geometry, but crystallographic defects are induced in the surface leading to reduced light output and efficiency
Solution Approach 1:
A dry etch process is performed immediately after the mesa etch process while the structures are still on the substrate. This preliminary treatment removes the defective surface layer created by the mesa etch before the structures are separated, preventing defect propagation and maintaining high light output efficiency in the final microLED structures
Solution Approach 2:
The defective surface layer containing crystallographic defects is selectively removed through the dry etch process. By extracting only the damaged outer layer while preserving the underlying healthy crystal structure, the solution eliminates the source of non-radiative recombination centers that would reduce light output
2Reliability
If a wet etch method is used to remove defective surface layers, then defects are removed, but the process is difficult to control causing shape alterations and uniformity issues
Solution Approach 1:
The wet chemical etch process is replaced with a dry etch process using plasma or gas-phase chemistry. This substitution provides superior process control through precise control of gas flow rates, pressure, and power parameters, enabling uniform defect removal while maintaining the original microLED structure geometry without the uncontrolled chemical attacks inherent in wet etching
Solution Approach 2:
The etch process parameters are optimized to achieve selective removal of only the defective surface layer. By controlling the dry etch duration, gas composition, and power levels, the process removes approximately 1-10 nm of surface material containing defects while preserving the underlying crystal structure and maintaining precise geometric control over the microLED structures
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 dry etch process effectively removes defects without altering the shape or geometry of microLED structures, improving light output and efficiency while maintaining control and repeatability across multiple wafers.
Implementation Method 1
A dry etch process using alternating cycles of chlorine and argon gases in an inductively coupled plasma or reactive thermal process to selectively remove the defective surface layers
Implementation Method 2
flowing a second gas to selectively remove the layer on the surface of the microLED structure
Data Source
AI summary
A mesa etch may form the geometry of microLED structures. However, the mesa etch may induce defects in the microLED structures that decreases the efficiency of the microLEDs. To correct these defects, a dry etch process may be performed that incrementally removes the surface layers of the microLED structures with the defects. The dry etch may be configured to incrementally remove a small outer layer, and thus may preserve the overall shape of the microLED structures while leaving a smooth surface for the application of a dielectric layer. The dry etch process may include two steps that are repeatedly performed. A first gas may react with the surface to form a gallium compound layer, and a second gas may then selectively remove that layer. The dry etch may include plasma-based etches or reactive thermal etches.