3D Stacked LED Structure via Oxide Bonding for Thermal Management
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Solution Overview
Problem
Current methods for constructing RGB LEDs are inefficient and costly, particularly due to issues with light mixing, thermal expansion coefficient mismatches, and high processing temperatures, which hinder the development of cost-effective and efficient white LED solutions for lighting and display applications.
Innovation Solution
The use of smart layer transfer techniques, such as ion-cut and laser lift-off, combined with oxide-to-oxide bonding and conductive oxide bonding, allows for the stacking of red, green, and blue LEDs on a silicon sub-mount, enabling efficient light emission and reducing processing temperatures below 450°C, thereby mitigating thermal expansion issues and improving manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional methods for constructing RGB LEDs are used, then light mixing issues and thermal expansion coefficient mismatches occur, but processing temperatures must be kept below 450°C to mitigate thermal stress
Solution Approach 1:
The patent segments the LED construction into separate red, green, and blue LED layers that are stacked individually on the silicon sub-mount. Each layer is transferred separately using smart layer transfer techniques, allowing independent optimization of each layer's thermal and mechanical properties without being constrained by high-temperature processing that would cause thermal expansion mismatches.
Solution Approach 2:
The patent introduces an oxide bonding interface as an intermediary between the stacked LED layers and the silicon sub-mount. This oxide layer serves as a thermal and mechanical buffer that accommodates thermal expansion coefficient differences between the various LED materials and silicon, enabling low-temperature processing below 450°C while maintaining structural reliability.
2Ease of manufacture
If smart layer transfer techniques and oxide-to-oxide bonding are used, then manufacturing cost and processing temperature are reduced, but light mixing efficiency must be improved
Solution Approach 1:
The patent transitions from planar LED construction to three-dimensional stacked LED architecture. By stacking red, green, and blue LEDs vertically on a silicon sub-mount rather than arranging them horizontally, the patent achieves improved light mixing efficiency through spatial separation while maintaining a compact footprint. This vertical stacking enables better thermal management and independent optimization of each color layer.
Solution Approach 2:
The patent applies local quality optimization by allowing each stacked LED layer to have tailored optical and electrical properties specific to its color function. The oxide bonding interfaces and contact structures are locally optimized for each layer's requirements, enabling cost-effective manufacturing through standardized transfer techniques while maintaining high light mixing efficiency through customized layer designs.
3Illumination intensity
If stacked LED structure is implemented, then light mixing is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal oxide-to-oxide bonding technique that can be applied to transfer and stack multiple types of LED layers (red, green, blue) on a common silicon sub-mount. This universal bonding approach simplifies the manufacturing process by using the same bonding methodology for all layers, reducing device complexity despite the multi-layer stacked structure. The oxide bonding interface serves multiple functions including mechanical attachment, thermal management, and stress relief.
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 enables the creation of efficient, cost-effective RGB LEDs with improved light mixing and reduced thermal stress, enhancing the performance and affordability of white LED solutions for various applications, including lighting and displays.
Implementation Method 1
an oxide layer disposed between said first level and said second level, wherein said second level is bonded to said oxide layer, and wherein said bonded comprises oxide to oxide bonds
Data Source
AI summary
A 3D micro display, the 3D micro display including: a first single crystal layer including at least one LED driving circuit; a second single crystal layer including a first plurality of light emitting diodes (LEDs), where the second single crystal layer includes at least ten individual first LED pixels; and a second plurality of light emitting diodes (LEDs), where the first plurality of light emitting diodes (LEDs) emits a first light with a first wavelength, where the second plurality of light emitting diodes (LEDs) emits a second light with a second wavelength, where the first wavelength and the second wavelength differ by greater than 10 nm, and where the 3D micro display includes an oxide to oxide bonding structure.