Self-aligned collimation grid for light emitting diodes
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Solution Overview
Problem
Current methods for producing a collimation grid on light emitting and/or light receiving devices, especially those emitting/receiving light from the rear face, face challenges in achieving high aspect ratio and precise alignment, leading to optical losses and mechanical instability.
Innovation Solution
A method involving the production of a stack of semiconductor layers with etching and dielectric portions to form self-aligned conductive portions acting as both electrodes and a collimation grid, allowing for high aspect ratio and precise alignment before substrate removal, thus minimizing optical losses and mechanical issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the collimation grid is produced by transferring after device fabrication, then alignment precision with pixels can be achieved, but the aspect ratio of the collimation grid walls is limited and mechanical stability deteriorates
Solution Approach 1:
The patent combines the formation of the collimation grid with the formation of the interconnection levels by using the same conductive material layers and processing steps. The collimation grid walls and electrodes are created simultaneously as integrated structures, eliminating the need for separate transfer operations and achieving both high alignment precision and mechanical stability.
Solution Approach 2:
The collimation grid structure is formed preliminarily during the interconnection level fabrication process before final device assembly. The conductive material is deposited and patterned to create both the electrodes and the collimation grid walls in advance, ensuring proper alignment with pixels and providing mechanical support during subsequent processing steps.
2Area of stationary object
If the collimation grid walls are made thin to minimize dead zone surface, then the useful surface of pixels is maximized, but the aspect ratio increases making production difficult
Solution Approach 1:
The patent changes the material parameters and deposition parameters to enable the formation of thin-walled collimation grid structures with high aspect ratios. By using specific conductive materials and controlling deposition conditions, the process achieves thin walls (less than 5 μm) with sufficient mechanical strength and proper aspect ratio (greater than 2) without compromising manufacturability.
3Reliability
If the collimation grid height is increased to improve optical separation, then directivity improves, but the complexity of production increases
Solution Approach 1:
The patent merges the collimation grid formation with the interconnection level fabrication process. The same conductive material layers that form the electrodes also form the collimation grid walls, and the same lithography and etching steps create both structures. This integration eliminates additional production steps while achieving the required optical separation and directivity performance.
Data Source
AI summary
A method is provided for producing a device with light emitting/light receiving diodes, including: producing, on a substrate, a stack including first and second doped semiconductor layers; first etching of the stack, forming first openings through the entire thickness of the second layer; producing dielectric portions covering, in the first openings, the side walls of the second layer; second etching of the stack, extending the first openings until reaching the substrate, delimiting the p-n junctions of the diodes; etching extending the first openings into a part of the substrate; producing first electrically conductive portions in the first openings, forming first electrodes of the diodes, and producing second electrodes electrically connected to the second layer; and eliminating the substrate, forming a collimation grid.