Current trends in electronic industry, such as Internet of Things (IoT) and Cloud Computing call for high interconnect
bandwidth, increased number of active devices and high IO count. Hence the integration of on silicon optical waveguides
becomes an alternative approach to cope with the performance demands. The application and fabrication of horizontal
(planar) and vertical (Through Silicon Vias - TSVs) optical waveguides are discussed here. Coupling elements are used to
connect both waveguide structures. Two micro-structuring technologies for integration of coupling elements are
investigated: μ-mirror fabrication by nanoimprint (i) and dicing technique (ii).
Nanoimprint technology creates highly precise horizontal waveguides with polymer (refractive index nC = 1.56 at 650 nm)
as core. The waveguide ends in reflecting facets aligned to the optical TSVs. To achieve Total Internal Reflection (TIR),
SiO2 (nCl = 1.46) is used as cladding. TSVs (diameter 20-40μm in 200-380μm interposer) are realized by BOSCH process1,
oxidation and SU-8 filling techniques. To carry out the imprint, first a silicon structure is etched using a special plasma
etching process. A polymer stamp is then created from the silicon template. Using this polymer stamp, SU-8 is imprinted
aligned to vertical TSVs over Si surface.Waveguide dicing is presented as a second technology to create coupling elements
on polymer waveguides. The reflecting mirror is created by 45° V-shaped dicing blade.
The goal of this work is to develop coupling elements to aid 3D optical interconnect network on silicon interposer, to
facilitate the realization of the emerging technologies for the upcoming years.
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