Optical Interposer Groove Fabrication via Selective Etching
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Solution Overview
Problem
Existing optical interposers face challenges in achieving precise fiber positioning and a denser, more compact structure due to limitations in groove shape and sidewall angle, which affects the pitch between fibers and the independence of groove width and spacing from depth.
Innovation Solution
The development of optical interposers with grooves having vertical or angled sidewalls, allowing for precise fiber positioning and independent optimization of groove width and spacing, using a process that involves selective etching and multiple etch-stop layers to achieve high depth uniformity and integration with conductive lines and circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If V-grooves with 45° sidewalls are used for fiber positioning, then precise fiber positioning is achieved, but the pitch between fibers increases and the structure becomes less compact
Solution Approach 1:
The patent changes the groove geometry parameters from V-grooves with 45° sidewalls to rectangular grooves with vertical sidewalls. This parameter change allows the groove width to be independent of groove depth, enabling reduced pitch between fibers while maintaining precise positioning capability, thus improving area utilization without sacrificing positioning precision.
2Manufacturing precision
If groove width and spacing are dependent on groove depth (as in V-grooves), then fiber positioning is determined by groove geometry, but the design flexibility for circuitry integration is reduced
Solution Approach 1:
The patent segments the groove dimensions into independent parameters: groove width, groove depth, and spacing between grooves. By using rectangular grooves with vertical sidewalls, the width and spacing can be independently optimized without being coupled to depth, providing design flexibility for integrating circuitry while maintaining manufacturing precision through independent parameter control.
3Area of stationary object
If rectangular grooves with vertical sidewalls are used, then a denser and more compact structure is achieved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent replaces mechanical V-groove formation processes with a combination of photolithography and reactive ion etching (RIE) to create rectangular grooves with vertical sidewalls. This substitution of manufacturing methods enables precise control of groove geometry and vertical sidewalls, achieving compact structure while managing fabrication complexity through standard semiconductor processing techniques.
4Manufacturing precision
If multiple etch-stop layers are used to achieve high depth uniformity, then groove depth precision is improved, but the fabrication process steps increase
Solution Approach 1:
The patent introduces etch-stop layers as intermediary elements during the reactive ion etching process. These etch-stop layers act as mediators to precisely control the etching depth and ensure uniform groove depth across the substrate. By using materials with distinct etch selectivity, the process achieves high depth precision while the etch-stop layers are later removed, minimizing their impact on the final structure.
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 enables a denser, more compact optical interposer design with improved fiber positioning and flexibility in using the interposer area for circuitry or mechanical support, while maintaining high precision and uniformity in groove formation.
Implementation Method 1
a process that involves selective etching and multiple etch-stop layers to achieve high depth uniformity
Data Source
AI summary
An optical interposer includes grooves (310) for optical fiber cables (104) coupled to a transducer (120). The grooves are formed by etching a cavity (410) in a substrate (130), filling the cavity with some layer (520), then etching the layer to form the grooves. The cavity has outwardly sloped sidewalls on which mirrors (144) are later formed. The groove etch is selective not to damage the sidewalls. The groove depth is uniform due to high etch selectivity of the layer, and also because of good control over the cavity etch due to the low aspect ratio of the cavity. Electrical circuitry for connection to the transducer is fabricated after the cavity filling but before the groove etch. The cavity filling leaves the wafer planar, facilitating fabrication of the electrical circuitry. Grooves can be provided on top and bottom of the interposer. Other features are also provided.