Direct-Bonded Micro-LED Arrays With Coplanar CMOS Contacts
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Solution Overview
Problem
Current microLED (mLED) display technology has not been widely mass-produced or commercialized, despite offering greater contrast, faster response times, and lower energy consumption compared to conventional LCDs.
Innovation Solution
The development of direct-bonded LED arrays, where micro-LED structures with coplanar electrical contacts are directly bonded to CMOS driver circuits, enabling the creation of transparent and flexible mLED array displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If microLED structures are directly bonded to CMOS driver circuits using conventional bonding methods, then manufacturing complexity and production time increase, but mass production capability is limited
Solution Approach 1:
The patent applies preliminary action by fabricating coplanar electrical contacts on the microLED structures before the bonding process. This pre-positioning of contacts in a coplanar configuration on the bonding interface surface enables direct alignment and bonding with CMOS driver circuits, eliminating the need for complex post-bonding wire bonding or TAB processes, thereby enabling mass production
Solution Approach 2:
The patent extracts the electrical contact function from the bonding interface by incorporating coplanar contacts directly on the microLED bonding surface. This separation of contact function from traditional edge-contact configurations allows the bonding interface to serve dual purposes: mechanical bonding and electrical connection, simplifying the overall manufacturing process
2Ease of manufacture
If conventional LED structures with non-coplanar contacts are used, then electrical connection to driver circuits becomes complex, but manufacturing simplicity is reduced
Solution Approach 1:
The patent merges the mechanical bonding function and electrical connection function into a single coplanar contact configuration on the bonding interface. The coplanar contacts are positioned on the same surface as the bonding interface, allowing simultaneous achievement of mechanical attachment and electrical connection, thereby simplifying the manufacturing process
Solution Approach 2:
The bonding interface surface serves multiple functions: it provides the mechanical bonding surface for attaching microLEDs to CMOS driver circuits, and simultaneously houses the coplanar electrical contacts for electrical connection. This multi-functionality eliminates the need for separate contact structures, simplifying manufacturing
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 facilitates the mass production of mLED array displays, providing high brightness, high contrast, and long product life, making them suitable for applications such as automotive, virtual reality, and augmented reality displays.
Implementation Method 1
The coplanar electrical contacts of the flat bonding interface are direct-bonded to electrical contacts of CMOS driver circuits on a second wafer
Data Source
AI summary
Direct-bonded LED arrays and applications are provided. An example process fabricates a LED structure that includes coplanar electrical contacts for p-type and n-type semiconductors of the LED structure on a flat bonding interface surface of the LED structure. The coplanar electrical contacts of the flat bonding interface surface are direct-bonded to electrical contacts of a driver circuit for the LED structure. In a wafer-level process, micro-LED structures are fabricated on a first wafer, including coplanar electrical contacts for p-type and n-type semiconductors of the LED structures on the flat bonding interface surfaces of the wafer. At least the coplanar electrical contacts of the flat bonding interface are direct-bonded to electrical contacts of CMOS driver circuits on a second wafer. The process provides a transparent and flexible micro-LED array display, with each micro-LED structure having an illumination area approximately the size of a pixel or a smallest controllable element of an image represented on a high-resolution video display.