Laser Lift-Off Transfer of Micro LED Chips on Rigid Carriers
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Solution Overview
Problem
Existing methods for transferring small semiconductor chips, such as LED chips, are inefficient and prone to errors due to the use of mechanically flexible foils, which lack sufficient strength and accuracy for small chips with dimensions of at most 130 μm, and cannot handle thin chips without bonded carriers effectively.
Innovation Solution
A method utilizing a laser lift-off process without film processes or mechanically flexible auxiliary carriers, where semiconductor chips are detached from a growth substrate using a separation layer that absorbs laser radiation, allowing for efficient transfer and attachment to rigid carriers, maintaining chip grid integrity and enabling precise detachment and placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If mechanically flexible foils are used for transferring small semiconductor chips, then the transfer process can be performed, but the foils lack sufficient strength and accuracy for small chips with dimensions of at most 130 μm
Solution Approach 1:
The patent replaces the mechanical foil-based transfer system with a laser-induced transfer system. Laser radiation is used to locally heat and detach chips from the growth substrate, eliminating the need for mechanically flexible foils. This substitution enables precise handling of small chips (≤130 μm) while maintaining ease of operation through contactless, highly controlled transfer.
2Ease of operation
If mechanically flexible foils are used for chip transfer, then the process can be performed, but it cannot handle thin chips without bonded carriers effectively
Solution Approach 1:
The laser-induced transfer method replaces mechanical foil handling, enabling effective transfer of thin chips without bonded carriers. The optical-based detachment mechanism provides gentle, localized force that does not mechanically stress thin chip structures, thereby expanding the method's adaptability to handle various chip thicknesses and configurations.
Solution Approach 2:
The patent introduces a sacrificial separation layer as an intermediary between the chip and growth substrate. This layer absorbs the laser energy and facilitates clean detachment, acting as a mediator that protects thin chips from direct mechanical contact and stress during the transfer process.
3Productivity
If conventional transfer methods are used, then the process can be performed, but it is inefficient and prone to errors
Solution Approach 1:
The laser-induced transfer method enables continuous, sequential detachment and transfer of chips without interruption. The laser beam can rapidly move between chips, maintaining continuous productive action while minimizing transfer time and reducing opportunities for errors, thereby improving both efficiency and reliability.
Solution Approach 2:
The method employs self-aligned transfer where chips are automatically positioned on the target substrate through the laser detachment process and gravitational or capillary forces, eliminating the need for complex manual positioning systems. This self-service mechanism reduces human intervention and associated errors while maintaining high transfer efficiency.
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 simplifies the transfer process, saves time, and improves deposition accuracy for small semiconductor chips, allowing for parallel transfer and selective release of chips, reducing mechanical and electrical handling issues, and enabling the use of hard carriers for efficient chip placement.
Implementation Method 1
The laser radiation is absorbed in the separation layer. As a result, the separation layer is decomposed.
Implementation Method 2
The laser radiation is absorbed in the separation layer. As a result, the separation layer is decomposed. Due to the destruction of the separation layer by the laser radiation, a mechanical connection between the semiconductor bodies and the growth substrate is mainly or completely lost.
Data Source
AI summary
In an embodiment a method includes providing a growth substrate with a plurality of semiconductor bodies for the semiconductor devices, wherein each semiconductor body comprises electrical contact structures and a separation layer arranged towards the growth substrate, arranging a rigid first auxiliary carrier on a side of the semiconductor bodies facing away from the growth substrate, wherein the first auxiliary carrier comprises a first detachment layer, detaching the growth substrate by laser radiation, wherein the laser radiation is absorbed in the separation layer, arranging a rigid second auxiliary carrier on a side of the semiconductor bodies facing away from the first auxiliary carrier, wherein the second auxiliary carrier comprise a second detachment layer, detaching the first auxiliary carrier by laser radiation, wherein the laser radiation is absorbed in the first detachment layer and the separation layer still extending continuously over the growth substrate while detaching and mechanically and electrically arranging the semiconductor bodies on at least one permanent carrier.