Redundant LED Mesa for Micro-Display Yield
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Solution Overview
Problem
The transfer-bonding technique for light-emitting diode (LED) chips in monolithic micro-displays faces challenges with low manufacturing yield and high costs due to alignment accuracy issues and the need for redundant chips, which also complicates achieving high-resolution displays.
Innovation Solution
Incorporating redundant light-emitting mesas in each LED chip, allowing the control circuit to switch from a defective display mesa to a redundant mesa if it fails, thereby maintaining display functionality without replacing the chip or increasing pixel size or pitch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If transfer-bonding technique is used to bond LED chips to substrate, then brightness and display quality are enhanced, but manufacturing yield is low and alignment accuracy is poor
Solution Approach 1:
The patent applies preliminary action by pre-forming redundant light-emitting mesas within each LED chip during the epitaxial growth process, before the chips are transferred to the final substrate. This advance preparation ensures that backup light-emitting structures are already in place, enabling immediate failover if the primary mesa fails, thereby improving manufacturing yield without compromising display quality
Solution Approach 2:
The patent implements beforehand cushioning by incorporating redundant light-emitting mesas that serve as backup structures. These redundant mesas are prepared in advance within each chip, providing a cushion against potential failures of the primary light-emitting mesa. This ensures continuous display functionality even when alignment or bonding issues occur during manufacturing
2Productivity
If redundant LED chips are used to replace dysfunctional chips, then manufacturing yield is improved, but more chips are required and costs increase
Solution Approach 1:
The patent merges the primary and redundant light-emitting mesas into a single integrated LED chip structure. Instead of using separate backup chips, both the primary light-emitting mesa and redundant light-emitting mesas are formed within the same chip during epitaxial growth. This consolidation reduces the total number of chips needed while maintaining the ability to replace dysfunctional mesas, thereby improving manufacturing yield without increasing chip quantity
Solution Approach 2:
The patent applies universality by designing each LED chip to perform multiple functions: the primary light-emitting mesa serves normal display functions, while the integrated redundant light-emitting mesas serve as backup structures. This multi-functionality allows a single chip to both display and provide self-repair capability, eliminating the need for additional dedicated backup chips
3Productivity
If excessive redundant LED chips are used, then manufacturing yield is improved, but distance among chips increases which is unfavorable for high-resolution display
Solution Approach 1:
The patent applies the nested doll principle by embedding redundant light-emitting mesas within the same physical footprint as the primary light-emitting mesa. The redundant structures are nested inside the chip structure, sharing the same space rather than requiring additional external space. This allows high-resolution displays with small dot pitch to maintain manufacturing yield improvements without increasing overall chip spacing
4Adaptability or versatility
If wavelength conversion materials are used for colorization, then different color beams can be emitted, but conversion efficiency is low and coating uniformity is poor
Solution Approach 1:
The patent extracts the colorization function from external wavelength conversion materials and integrates it directly into the LED chip structure through epitaxially grown light-emitting layers with different bandgaps. By taking out the reliance on separate conversion materials and embedding the color-emitting capability within the semiconductor structure itself, the patent achieves superior conversion efficiency and uniformity compared to external phosphor approaches
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 enhances manufacturing yield and reduces costs by allowing defective LEDs to be repaired in place, maintaining display quality without increasing pixel dimensions or pitch, thus improving the overall efficiency of the display panel.
Implementation Method 1
An inorganic light-emitting diode (LED) display characterized by capability of emitting light and high brightness
Data Source
AI summary
A display pixel suitable for being arranged on a carrier is provided. The display pixel includes a plurality of light-emitting diode chips. The light-emitting diode chips are disposed on and electrically connected to the carrier. Each of the light-emitting diode chips respectively serves as a sub-pixel and includes a semiconductor device layer, and the semiconductor device layer includes a display light-emitting mesa and at least one redundant light-emitting mesa. During a period of driving each of the light-emitting diode chips, one of the display light-emitting mesa and the at least one redundant light-emitting mesa in each of the light-emitting diode chips is capable of emitting light. A display panel including a plurality of the display pixels mentioned above is also provided.