Elastomeric Interface Layer for Micro-LED Transfer
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Solution Overview
Problem
The challenge in semiconductor device fabrication lies in the difficulty of transferring and placing micro-LEDs of varying colors onto display substrates without damaging them, especially as their form factor decreases, due to the complexity of adhesive attachment and precise placement.
Innovation Solution
The formation of an elastomeric interface layer over micro-LED dies using photoresist materials, where light exposure selectively insolubilizes portions of the photoresist to facilitate the deposition of elastomeric material, allowing for effective adhesion with a pick-up head during the manufacturing of electronic displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If micro-LEDs are transferred using conventional picking and placing methods, then the LEDs can be moved between substrates, but the process becomes increasingly difficult and damage risk increases as LED form factor decreases
Solution Approach 1:
An elastomeric interface layer is introduced as an intermediary between the micro-LED dies and the pick-up head. This layer facilitates adhesive attachment by providing a compliant surface that conforms to the LED geometry, enabling reliable transfer of miniaturized LEDs without direct mechanical contact that could cause damage
Solution Approach 2:
The mechanical properties of the interface are changed by using an elastomeric material with specific durometer hardness (e.g., 20-40 Shore A) that provides both adhesion and compliance. This parameter optimization enables effective picking and placing of micro-LEDs while protecting against damage during handling
2Ease of operation
If an elastomeric interface layer is formed to facilitate adhesive attachment, then picking and placing becomes easier, but the fabrication process complexity increases
Solution Approach 1:
The mechanical process of forming the elastomeric interface layer is replaced by a photolithography-based approach. Photoresist material is deposited and selectively exposed through the LED array, using light absorption differences to define the interface layer pattern, thereby simplifying the fabrication process
Solution Approach 2:
The LED dies themselves serve as the photomask during the elastomeric layer formation process. By exploiting the light-absorbing properties of the LED structures, the pattern transfer is achieved without requiring separate masking steps, reducing overall process complexity
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 method enables efficient and precise transfer and placement of micro-LEDs onto display substrates, enhancing the adhesion with pick-up heads and reducing damage risks, thereby improving the manufacturing process for electronic displays.
Implementation Method 1
A portion of the light incident on the LED dies is absorbed by the LED dies to retain soluble first portions of the photoresist material on the LED dies
Implementation Method 2
Other portions of photoresist material between the LED dies are exposed to the light, causing second portions of the photoresist material between the LED dies to become insoluble
Data Source
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AI summary
An elastomeric interface layer (elayer) is formed over multiple light emitting diode (LED) dies by depositing photoresist materials across multiple LED dies, and using the LED dies as a photolithography mask to facilitate formation of the elayer on each LED die. The elayer facilitates adhesive attachment of each LED die with a pick and place head (PPH), allowing the LED dies to be picked up and placed onto a display substrate including control circuits for subpixels of an electronic display. In some embodiments, the LED dies are micro-LED (µLED) dies.