Optical Interposer Mating with PIC Die Using Index-Matching Underfill
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Efficiently and cost-effectively aligning optics to couple light into and out of photonic integrated circuits (PICs) is challenging, as existing methods are slow, incompatible with conventional semiconductor packaging processes, and result in yield and throughput issues.
Innovation Solution
An optical interposer is mated with a PIC die, featuring aligned waveguides and secured using a mechanical adhesive, with an index-matching material improving coupling between the PIC die and the optical interposer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optical fiber arrays are attached to PICs using conventional methods, then optical coupling is achieved, but manufacturing speed is slow and yield is reduced
Solution Approach 1:
The system is divided into separate components: an optical interposer with waveguide arrays and PICs with waveguide interfaces. The optical interposer is prepared independently on a separate substrate, then laterally transferred and bonded to the PICs. This segmentation allows parallel processing of multiple PICs simultaneously, dramatically increasing manufacturing throughput while maintaining alignment precision through the interposer's reference features.
Solution Approach 2:
An optical interposer acts as an intermediary component between optical fiber arrays and PICs. The interposer contains waveguide arrays that interface with both the PIC waveguides and external optical fibers. This intermediary enables standardized, high-speed bonding processes while maintaining precise optical coupling, resolving the contradiction between manufacturing speed and alignment accuracy.
2Adaptability or versatility
If optical fiber arrays are attached to PICs, then optical coupling is achieved, but compatibility with conventional semiconductor packaging is lost
Solution Approach 1:
The optical interposer serves multiple functions: it provides optical waveguiding, mechanical support, alignment reference features, and bonding interfaces. By consolidating these functions into a single component that can be processed using conventional semiconductor techniques, the system achieves compatibility with existing packaging infrastructure while enabling complex optical interconnections.
Solution Approach 2:
The bonding process parameters are optimized to match conventional semiconductor packaging processes. The lateral transfer and bonding steps use temperatures, pressures, and materials compatible with standard semiconductor manufacturing equipment and processes, enabling seamless integration into existing production lines without requiring specialized equipment.
3Manufacturing precision
If optical fiber arrays are attached to PICs, then optical coupling is achieved, but alignment precision is compromised
Solution Approach 1:
Alignment reference features are fabricated into the optical interposer during its initial processing, before bonding to the PICs. These pre-formed reference features (such as alignment marks and mechanical guides) enable rapid, precise alignment during the bonding step, eliminating time-consuming alignment procedures and enabling high-throughput manufacturing with maintained precision.
Solution Approach 2:
The optical interposer replicates the waveguide geometry and spacing from the PIC design, creating a precise optical interface. By copying the critical dimensional parameters and using the interposer as a master template, consistent alignment precision is achieved across multiple PICs manufactured in parallel, maintaining both throughput and precision.
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 flexibility, performance, and yield by providing a robust and efficient method for aligning optics within PICs.
Implementation Method 1
an index-matching material between the one or more waveguides of the PIC die and the one or more waveguides of the optical interposer
Data Source
AI summary
In an illustrative embodiment, mechanical adhesive and a separate index-matching material are used as underfill between a photonic integrated circuit (PIC) die and an optical interposer. The index-matching material reduces coupling loss between waveguides of the PIC die and waveguides of the optical interposer, while the mechanical adhesive secures the optical interposer in place. The mechanical adhesive can be thermally cured, have a low coefficient of thermal expansion (CTE), have high viscosity, and have a relatively high optical transmission loss. The index-matching material can have low optical transmission loss, be UV cured, have a relatively high CTE, and have low viscosity. The combination of mechanical adhesive and index-matching material can improve ease of manufacture and yield. Additional features are disclosed, such as V-groove arrays in the optical interposer and the PIC die that have low stress and trenches and walls to control flow of the mechanical adhesive and/or index-matching material.