Printable Micro-LED Structures With Transfer Printing on Sapphire
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Solution Overview
Problem
The existing methods for producing micro-light-emitting diodes (micro-LEDs) on sapphire substrates are costly and inefficient due to lattice structure mismatches, leading to defects and reduced performance, and require complex processing steps for electrical interconnections.
Innovation Solution
The development of micro-transfer printing methods and structures that allow for the formation and assembly of micro-LEDs on sapphire substrates with simplified electrical interconnections, using sacrificial layers and interlayers to facilitate the release and printing of semiconductor elements onto various substrates, enabling high-performance arrays with reduced processing steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If micro-LEDs are formed on sapphire substrates using conventional methods, then the crystal structure performance is improved, but the manufacturing cost and processing complexity increase
Solution Approach 1:
The patent divides the micro-LED fabrication process into two independent stages: (1) growing high-quality GaN crystal structures on sapphire substrates, and (2) transferring the completed micro-LEDs to final substrates via micro-transfer printing. This segmentation allows each stage to be optimized independently, maintaining crystal quality while simplifying the overall manufacturing process.
Solution Approach 2:
The patent introduces a sacrificial layer as an intermediary between the sapphire substrate and the micro-LED structure. This layer enables controlled release of the micro-LEDs during transfer printing, facilitating the separation of crystal growth and device assembly processes without compromising the integrity of either stage.
2Reliability
If conventional electrical interconnection methods are used for micro-LEDs, then reliable electrical connections are achieved, but the number of processing steps increases
Solution Approach 1:
The patent combines multiple functions into the contact layer: it serves as both the electrical interconnection medium and the release layer for micro-transfer printing. This merging eliminates the need for separate electrical connection steps, reducing processing complexity while maintaining reliable electrical contacts between micro-LEDs and the substrate.
3Manufacturing precision
If micro-LEDs are assembled using conventional means, then precise positioning is achieved, but the assembly cost and complexity increase
Solution Approach 1:
The patent performs preliminary positioning of micro-LEDs during the crystal growth stage on the sapphire substrate, where precise placement can be achieved. The micro-LEDs are then transferred as pre-positioned units to the final substrate, eliminating the need for complex post-assembly positioning operations and reducing manufacturing costs.
Data Source
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AI summary
The present invention provides structures and methods that enable the construction of micro-LED chiplets formed on a sapphire substrate that can be micro- transfer printed. Such printed structures enable low-cost, high-performance arrays of electrically connected micro-LEDs useful, for example, in display systems. Furthermore, in an embodiment, the electrical contacts for printed LEDs are electrically interconnected in a single set of process steps. In certain embodiments, formation of the printable micro devices begins while the semiconductor structure remains on a substrate. After partially forming the printable micro devices, a handle substrate is attached to the system opposite the substrate such that the system is secured to the handle substrate. The substrate may then be removed and formation of the semiconductor structures is completed. Upon completion, the printable micro devices may be micro transfer printed to a destination substrate.