Microdevice Substrate Integration for Reliable Pixel Circuit Bonding
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Solution Overview
Problem
The challenge lies in efficiently integrating millions of microdevices with circuits for every pixel with proper yield, particularly due to issues with transfer processes and bonding repeatability and reliability at small pad sizes, which affect yield and lifetime.
Innovation Solution
The integration process involves transferring microdevices to a system substrate, forming a protective layer, patterning it for conductive electrodes, and connecting backplane elements, using methods like electrostatic transfer heads and elastomer transfer heads, along with reflective layers to enhance light output uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If microdevices are transferred to system substrate using conventional methods, then integration is achieved, but transfer process reliability and bonding repeatability deteriorate at small pad sizes
Solution Approach 1:
The patent segments the transfer process into multiple controlled stages using a multi-layer substrate structure. The microdevice is first transferred to an intermediate substrate with alignment marks, then to the final system substrate. This segmentation allows each transfer step to be optimized independently, improving overall reliability at small pad sizes while maintaining high productivity through automated processes.
Solution Approach 2:
The patent introduces an intermediate substrate as a mediator in the transfer process. This intermediate substrate serves as a temporary platform that facilitates precise alignment and bonding before final integration. The intermediate substrate with its alignment mark structure acts as a buffer that enhances bonding repeatability without compromising transfer efficiency.
2Productivity
If microdevices are integrated with circuits for every pixel, then system performance improves, but manufacturing complexity and yield challenges increase
Solution Approach 1:
The patent performs preliminary actions by pre-configuring alignment marks and circuit patterns on the substrate before microdevice transfer. The substrate is prepared with predefined bonding regions and electrical connection paths, which simplifies the subsequent integration process. This preliminary preparation reduces manufacturing complexity during the actual transfer and integration stages while enabling high-performance pixel-level circuit integration.
Solution Approach 2:
The patent utilizes parameter changes in the substrate structure, such as varying thickness, material composition, and optical properties across different regions. These parameter variations enable precise control over the transfer process and final device performance, allowing complex pixel-level integration to be achieved through controlled parameter modifications rather than complex processing steps.
3Loss of time
If transfer process is optimized for speed, then productivity improves, but bonding repeatability and reliability worsen
Solution Approach 1:
The patent implements periodic action through a cyclic transfer process that repeats standardized steps: alignment, bonding, and verification. Each cycle is optimized for both speed and reliability, with the periodic nature allowing for consistent quality control. The rhythmic repetition of proven process steps maintains bonding reliability while achieving high throughput through efficient cycle management.
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 approach improves the integration process efficiency, reduces time and enhances the uniformity and reliability of microdevice circuits, thereby improving system performance and yield.
Implementation Method 1
using methods like electrostatic transfer heads and elastomer transfer heads
Implementation Method 2
using methods like electrostatic transfer heads and elastomer transfer heads
Implementation Method 3
along with reflective layers to enhance light output uniformity
Data Source
AI summary
An integrated optical display system includes a backplane with appropriate electronics, and an array of micro-devices. A touch sensing structure may be integrated into the system. In one embodiment, an integrated circuit and system is integrated on top of micro-devices transferred to a substrate. Openings in a planarization layer (or layers) may be provided to connect the micro-devices with electrodes and other circuitry. Light reflectors may be used to redirect the light, and color conversion layers or color filters may be integrated before the micro-devices or on the substrate surface opposite to the surface of micro-devices.