Stacked Display Pixel Wafer Pairing for Higher Fabrication Yield
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Solution Overview
Problem
The yield of light emitting devices with a stacked structure is low due to defective locations on individual wafers, leading to significant losses as favorable locations on other wafers are discarded during the fabrication process.
Innovation Solution
A method involving measuring emission wavelengths on wafers, forming test stacked structures, calculating combination yields based on overlapping defective locations, and selecting optimal wafer combinations for subsequent processing to maximize yield, including using a computational program to determine and compare yields across different combinations of wafers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wafers are stacked to form a light emitting device with a stacked structure, then the number of LED chips is reduced and fabrication time is shortened, but the overall yield decreases due to defective locations on individual wafers
Solution Approach 1:
The patent applies preliminary action by measuring emission wavelengths and identifying defective locations on each wafer before stacking. This allows the system to pre-determine which wafers can be successfully combined, preventing waste of favorable locations during the stacking process. The computational program calculates combination yields in advance to guide wafer selection and arrangement.
Solution Approach 2:
The patent changes the parameter of wafer selection from random or sequential to optimized based on emission wavelength measurements. By varying which wafers are stacked together based on their measured characteristics and calculated combination yields, the system maximizes the number of functional subpixels in the final device.
2Ease of manufacture
If all wafers are stacked together regardless of defective locations, then the fabrication process is simplified, but favorable locations on good wafers are discarded due to defects on other wafers
Solution Approach 1:
The patent performs preliminary measurement of emission wavelengths and identification of defective locations before stacking. This preliminary action enables the computational program to calculate which wafer combinations will maximize yield, preventing the waste of favorable locations that would occur with random stacking.
Solution Approach 2:
The patent implements feedback by using measurement results of emission wavelengths to guide the stacking process. The computational program receives data about defective locations on each wafer and uses this feedback to determine optimal wafer combinations, ensuring that favorable locations are not wasted.
3Reliability
If emission wavelength measurement and combination yield calculation are performed for all wafer combinations, then optimal wafer selection is achieved, but measurement and processing time increase
Solution Approach 1:
The patent applies segmentation by dividing the wafer group into manageable units and measuring emission wavelengths at predetermined locations on each wafer separately. The computational program then processes these segmented measurements to calculate combination yields, making the overall optimization process more efficient than treating all wafers as a single group.
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 fabrication yield of light emitting devices by identifying and utilizing optimal wafer combinations, reducing waste and increasing the efficiency of the manufacturing process.
Implementation Method 1
Light emitting diodes have been used in various fields including displays, vehicular lamps, general lighting, and the like. With various advantages such as long lifespan, low power consumption, and rapid response, light emitting diodes have been replacing existing light sources in the art.
Data Source
AI summary
A display apparatus includes multiple pixels. The pixels can emit one or more colors of light. Light of the same color emitted by two or more of the pixels can have wavelengths that differ by no more than one percent. The pixels can include a stacked structure including two or more subpixels, with each subpixel emitting light of a different color than the other subpixels in the stacked structure.