Integrated SiN on SOI dual photonic devices for advanced datacom solutions

Abstract

We report on the co-integration of an additional passive layer within a Silicon Photonic chip for advanced passive devices. Being a CMOS compatible material, Silicon Nitride (SiN) appears as an attractive candidate. With a moderate refractive index contrast compared to SOI, SiN based devices would be intrinsically much more tolerant to fabrication errors while keeping a reasonable footprint. In addition, it's seven times lower thermo-optical coefficient, relatively to Silicon, could lead to thermal-tuning free components. The co-integration of SiN on SOI has been explored in ST 300mm R&D photonic platform DAPHNE and is presented in this paper. Surface roughness of the SiN films have been characterized through Atomic Force Microscopy (AFM) showing an RMS roughness below 2nm. The film thickness uniformity have been evaluated by ellipsometry revealing a three-sigma of 21nm. Statistical measurements have been performed on basic key building blocks such as SiN strip waveguide showing propagation loss below 0.7dB/cm and 40µm radius bends with losses below 0.02dB/90°. A compact Si-SiN transition taper was developed and statistically measured showing insertion losses below 0.17dB/transition on the whole O-band wavelength range. Moreover, advanced WDM devices such as wavelength-stabilized directional couplers (WSDC) have been developed.

Scaling capacity of fiber-optic transmission systems via silicon photonics

“…56]. It was also demonstrated to be compatible with fabrication by deposition on top of patterned SOI wafers as an additional back-end-of-line process step [57][58][59]. Silicon nitride (Si 3 N 4 ) is a mid-index contrast optics (MiDex) material, transparent from the visible (∼0.4 µm) to the mid-IR (4 µm) and has a lower thermo-optic coefficient compared to silicon.…”

Open-Access Silicon Photonics: Current Status and Emerging Initiatives

“…Moreover, it is also possible to combine elements of different platforms together. The manufacturing flexibility of SiN layers makes it possible to integrate SiN layers into the SOI platforms [108], [135]- [139]. In such a platform, passive components demanding low loss and high fabrication tolerance are defined on the SiN layer [140], [141].…”

“…Performance of active devices has also benefited from the evolved processing technology whereby different types of efficient modulators and photo-detectors operating at high-speed are demonstrated [24]- [28], [31], [32], [156]- [161]. As a result of advances in the process technology, open-access fabs have consolidated their platforms by offering new process modules such as very low loss waveguides [156], [157], high-speed modulators [162]- [167], integration of efficient electro-optic materials in a silicon photonics process flow [174], [175], multi-layer SiN on Si [108], [135]- [139], and broadband fiber-chip-fiber couplers [168]- [173], [176].…”

Enhanced performance of integrated silicon nanophotonic devices engineered by sub-wavelength grating structures

“…On the other hand, integration of epitaxial III-V hetero-structures is even more challenging and comparatively complicated 11,12 . Furtheremore, the development of complex silicon nanophotonic devices and components calls upon multi-layer structuration's or multi-level etchings 13,14 . However, this comes hand-byhand with an additional fabrication and pre-or post-processing steps, which may be difficult to implement in some situations.…”

“…Restrictions in requirements for minimum feature sizes, mask-layer misalignments, and etching depth variations are also more apparent. Last, but not least, inclusion of novel, typically exotic materials may move the fabrication out from the well-developed silicon nanophotonics manufacturing conventions [10][11][12][13][14] .…”