Silicon Fiber Alignment Grooves for Thin Photonics Dies
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Solution Overview
Problem
Existing optical interconnect packages face challenges in achieving sub-micron alignment accuracy for optical fibers due to limitations in non-isotropic etching, which can cause cracking and limit the use of thin photonics dies and through-silicon vias, especially when multiple optical fibers need alignment in different directions.
Innovation Solution
Employing silicon groove architectures with 2-step lithographic etching and polymer guides for passive alignment, allowing for XY alignment accuracy and enabling the use of thin photonics dies with through-silicon vias, using etch stop materials and adhesive materials to guide optical fibers into grooves with precise alignment structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If non-isotropic etching is used to create alignment grooves, then alignment structure formation is achieved, but die cracking occurs and thin photonics dies with through-silicon vias cannot be used
Solution Approach 1:
The etching process is segmented into two distinct steps: first forming openings through the photonics die, then forming grooves in the substrate. This segmentation allows each step to be optimized independently, avoiding the cracking issues associated with non-isotropic etching while achieving precise alignment.
Solution Approach 2:
The alignment groove formation is extracted from the photonics die and relocated to the substrate. By forming grooves in the substrate rather than etching through the die, the patent eliminates the cracking problem while maintaining alignment functionality.
2Adaptability or versatility
If multiple optical fibers need to be aligned in different directions, then connectivity is improved, but non-isotropic etching limitations prevent achieving required alignment accuracy
Solution Approach 1:
The substrate groove structure serves multiple functions: it provides alignment references for optical fibers in different directions, supports thin photonics dies with through-silicon vias, and enables high-volume assembly. The groove architecture is designed to accommodate multi-directional fiber alignment requirements.
3Speed
If sub-um alignment accuracy is required for high-volume assembly, then data transfer speed is improved, but achieving this accuracy simultaneously for arrays of optical fibers is a significant challenge
Solution Approach 1:
Alignment grooves are formed in the substrate before optical fiber assembly. This preliminary action establishes precise alignment references that guide the placement of optical fibers, enabling sub-micron alignment accuracy to be achieved consistently across arrays during high-volume assembly.
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
Achieves less than 1 um alignment accuracy for optical fibers in different directions, reducing the risk of die cracking and enabling the use of thin photonics dies with through-silicon vias, thus supporting high-bandwidth, low-latency connectivity.
Implementation Method 1
adhesive material is in a bottom of the set of grooves
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3B
AI summary
A groove alignment structure comprises an etch stop material and a substrate over the etch stop material. A set of grooves is along a first direction in a top surface of the substrate, and adhesive material is in a bottom of the set of grooves. Optical fibers are in the set of grooves over the adhesive material and a portion of the optical fibers extends above the substrate. A set of polymer guides is along the first direction on the top surface of the substrate interleaved with the set of grooves. A method for fabricating a groove alignment structure, comprising: applying an etch stop material to a backside of a silicon substrate comprising a photonics die; performing a first etch process to form openings that define locations and widths of a plurality of grooves along a first direction in the silicon substrate; depositing polymer guides in-between the openings, the polymer guides running a same direction as the openings; performing a second etch process on the openings to remove silicon down to the etch stop material to form grooves; depositing an adhesive material into a bottom of the grooves; and inserting an optical fiber of an optical fiber array into respective ones of grooves.