Polymer Waveguide InFO Packaging for Optical IC Interconnects
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Solution Overview
Problem
Traditional fan-out type redistribution layers in wafer level packaging are limited in supporting optical interconnections, which offer higher performance compared to electrical interconnections, necessitating more efficient methods for optical interconnections within wafer level packages that include optical integrated circuits.
Innovation Solution
The implementation of integrated photonic-electric IC packages using polymer waveguides for optical interconnections, which provide higher communication performance and more compact structures, compatible with the InFO platform, and support inter-layer optical coupling through techniques like concave/bump, grating couplers, and reflective prisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fan-out type redistribution layers are used, then electrical interconnections are provided, but optical interconnection performance is limited
Solution Approach 1:
The redistribution layer is segmented into separate electrical and optical pathways. Electrical connections use traditional copper RDLs while optical connections use polymer waveguides with core-cladding structure, allowing each to be optimized independently for their respective functions
Solution Approach 2:
Polymer waveguides serve as intermediary structures between silicon photonic devices and optical fibers. The waveguides with their core-cladding structure mediate the optical signal transmission, enabling high-performance optical interconnections that bridge the gap between integrated photonic circuits and external optical fibers
2Reliability
If polymer waveguides with core and cladding layers are implemented, then optical signal transmission is enabled, but manufacturing complexity increases
Solution Approach 1:
The refractive index parameter is changed by using different polymer materials for the core and cladding layers. The core layer uses a higher refractive index polymer while the cladding uses a lower refractive index polymer, creating the optical waveguide effect through material parameter selection rather than complex geometric structures
Solution Approach 2:
The waveguide structure uses composite polymer materials with different optical properties. The core and cladding are made from different polymer compositions tailored to have specific refractive index differences, enabling optical confinement while maintaining compatibility with standard semiconductor fabrication processes
3Quantity of substance
If through-silicon vias and fan-out redistribution layers are integrated with waveguides, then high-density interconnects are achieved, but manufacturing process complexity increases
Solution Approach 1:
The electrical interconnection structure (through-silicon vias and copper RDLs) and optical waveguide structure are merged into a single integrated package. Both structures share the same substrate and are formed using compatible fabrication processes, allowing high-density interconnects to be achieved without requiring separate manufacturing lines
Solution Approach 2:
The polymer materials used in the waveguide cladding also serve as the mold compound material for the entire package. This multi-functional material selection simplifies the manufacturing process by eliminating separate molding steps and ensuring compatibility between optical and electrical components
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 substantially higher communication performance and more compact structures in wafer level platforms, achieving efficient optical interconnections within the wafer level package, overcoming the limitations of traditional electrical interconnections.
Implementation Method 1
utilizing a refractive index difference between core and cladding layers to guide light signals
Implementation Method 2
polymer waveguides for interfacing silicon photonics devices to optical fibers
Implementation Method 3
through-silicon vias and fan-out redistribution layers to enable high-density interconnects and inter-layer optical coupling
Data Source
AI summary
Disclosed are apparatus and methods for a silicon photonic (SiPh) structure comprising the integration of an electrical integrated circuit (EIC); a photonic integrated circuit (PIC) disposed on top of the EIC; two or more polymer waveguides (PWGs) disposed on top of the PIC and formed by layers of cladding polymer and core polymer; and an integration fan-out redistribution (InFO RDL) layer disposed on top of the two or more PWGs. The operation of PWGs is based on the refractive indexes of the cladding and core polymers. Inter-layer optical signals coupling is provided by edge-coupling, reflective prisms and grating coupling. A wafer-level system implements a SiPh structure die and provides inter-die signal optical interconnections among the PWGs.