Optoelectronic Device Manufacturing via Inverted LED Stack Bonding
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Solution Overview
Problem
The existing methods for manufacturing optoelectronic devices with gallium nitride LEDs face challenges in accurately aligning control circuits and LED arrays, particularly at high pixel densities, and struggle with achieving reliable electrical connections between the active LED stack and the control circuit, leading to potential mechanical and electric connection defects.
Innovation Solution
The method involves transferring an active diode stack with doped semiconductor layers onto a control circuit, forming trenches to delimit individual diodes, and using insulating layers for bonding, which allows for improved alignment and electrical connectivity by forming metallizations within these trenches to connect the semiconductor layers to the control circuit, ensuring robust mechanical and electrical bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the control circuit and LED array are separately manufactured and then hybridized by stacking, then the device can be assembled with modular components, but the alignment accuracy deteriorates making it difficult to achieve high resolution and pixel integration density
Solution Approach 1:
Instead of placing individual LEDs onto metal pads of the control circuit, the invention inverts the approach by placing a continuous active LED stack onto the control circuit and then structuring the stack to delimit individual LEDs. This eliminates the alignment problem by reversing the sequence of operations.
Solution Approach 2:
The control circuit is prepared in advance with metal pads and insulating structures before the LED stack is placed. The active LED stack is also prepared as a continuous layer with preliminary structuring, allowing subsequent definition of individual LED positions without alignment constraints during the bonding step.
2Reliability
If metal layers are deposited on both the control circuit and active LED stack for bonding, then electrical connection can be established, but bonding defects occur where metal layers fail to contact, causing electric connection failures
Solution Approach 1:
An insulating layer is introduced as an intermediary between the control circuit metal pads and the active LED stack. This insulating layer prevents direct metal-to-metal contact that causes bonding defects, while still allowing electrical connection through the insulating layer to be established reliably.
Solution Approach 2:
The bonding interface is segmented into distinct functional zones: metal pads on the control circuit, insulating layer in between, and the active LED stack. This segmentation allows each layer to be optimized independently and prevents the propagation of bonding defects across the interface.
Data Source
AI summary
A method of manufacturing an optoelectronic device, including: a) transferring, onto a connection surface of a control circuit, an active diode stack including at least first and second semiconductor layers of opposite conductivity types, so that the second semiconductor layer in the stack faces the connection surface of the control circuit and is separated from the connection surface of the control circuit by at least one insulating layer; b) forming in the active stack trenches delimiting a plurality of diodes, the trenches extending through the insulating layer and emerging onto the connection surface of the control circuit; and c) forming in the trenches metallizations connecting the second semiconductor layer to the connection surface of the control circuit.