Micro LED Display Panel Via Structure for Fracture-Free Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Micro LED chips face fractures during transfer due to laser lift off (LLO) process, primarily at steps where n-Pad and p-Pad are formed, and uneven adhesive force causes stress, leading to transfer failures.
Innovation Solution
A display panel design with a conductive via and conductive pattern portion on the undoped semiconductor layer, allowing for stable connection to the drive backplane, reducing stress and fractures by using a transparent conductive layer to connect P-type semiconductor layer without additional electrodes, and omitting the mesa process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If laser lift off is used to transfer Micro LED chips from growth substrate to transient substrate, then the transfer process can be automated, but the Micro LED chips are prone to fracture due to cracks at steps and uneven adhesive force
Solution Approach 1:
The patent segments the GaN layer into two parts: a lower GaN layer remaining on the growth substrate and an upper GaN layer transferred to the transient substrate. This segmentation allows the lower GaN layer to provide mechanical support during transfer, preventing chip fracture while enabling automated LLO process.
Solution Approach 2:
The patent performs preliminary formation of n-Pad and p-Pad electrodes on the growth substrate before the LLO transfer process. This preliminary action ensures that electrical connections are established before transfer, and the pads serve as anchoring points that prevent chip fracture during the automated transfer process.
2Ease of manufacture
If Mesa process is used to form n-Pad and p-Pad on steps, then electrical connections can be established, but cracks occur at steps causing chip fracture during transfer
Solution Approach 1:
The patent extracts the harmful steps structure created by Mesa process and removes it by performing LLO before Mesa etching. This eliminates the source of cracks while preserving the ability to form n-Pad and p-Pad electrodes on the flat GaN surface for electrical connections.
Solution Approach 2:
The patent performs preliminary formation of n-Pad and p-Pad electrodes on the growth substrate before the LLO transfer process. This preliminary action ensures that electrical connections are established before transfer, and the pads serve as anchoring points that prevent chip fracture during the automated transfer process.
3Reliability
If additional electrodes are fabricated to connect P-type semiconductor layer, then electrical connections are ensured, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent merges the functions of the P-type semiconductor layer and the p-Pad electrode into a single integrated structure. The P-type GaN layer itself serves as the electrode, eliminating the need for separate electrode fabrication steps while ensuring stable electrical connections.
Solution Approach 2:
The P-type GaN layer serves multiple functions: it acts as both the active semiconductor layer for light emission and as the p-Pad electrode for electrical connection. This multi-functionality reduces device complexity while maintaining connection reliability.
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
Improves transfer yield and reduces costs by minimizing fractures and uneven stress during LLO, ensuring stable electrical connections and uniform adhesive attachment.
Implementation Method 1
laser lift off is generally adopted, where GaN (gallium nitride) at the bottom of the Micro LED chip is irradiated by laser, so that the GaN decomposes into Ga and N2, separating the Micro LED from the growth substrate
Data Source
AI summary
A display panel includes a drive backplane and a plurality of light-emitting chips arranged on the drive backplane. Each of the light-emitting chips includes an N-type semiconductor layer, a multi-quantum well layer and a P-type semiconductor layer arranged on the undoped semiconductor layer in sequence and an undoped semiconductor layer. The undoped semiconductor layer is provided with a conductive via. The light-emitting chip further includes a conductive pattern portion, a part of the conductive pattern portion is located in the conductive via and is in contact with the N-type semiconductor layer, and another part of the conductive pattern portion protrudes from the conductive via and is connected to the drive backplane.