Ultra‐Low‐Loss Silicon Nitride Photonics Based on Deposited Films Compatible with Foundries

Ji, Xingchen; Okawachi, Yoshitomo; Gil-Molina, Andrés; Corato-Zanarella, Mateus; Roberts, Samantha P.; Gaeta, Alexander L.; Lipson, Michal

doi:10.1002/lpor.202200544

Cited by 22 publications

(13 citation statements)

References 39 publications

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“…All optical devices show intrinsic quality factors above 4.66 × 10 5 , with the highest being 5.7 × 10 5 , overall, more than 3 times higher than previous achievements with this material and waveguide propagation loss ranging between 0.78 and 1.07 dB/cm. These values are comparable to well-established platforms that can be deposited at low temperatures such as PECVD SiN at 350 °C (0.42 dB/cm). Additionally, using our ICPCVD optimized recipe, the a-SiC films can be deposited at 150 °C, which to our knowledge is the lowest temperature among other techniques and can be implemented with a variety of optical materials with a simple lift-off process.…”

Section: Introductionsupporting

confidence: 80%

High-Quality Amorphous Silicon Carbide for Hybrid Photonic Integration Deposited at a Low Temperature

Lopez-Rodriguez,

van der Kolk,

Aggarwal

et al. 2023

ACS Photonics

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Integrated photonic platforms have proliferated in recent years, each demonstrating its unique strengths and shortcomings. Given the processing incompatibilities of different platforms, a formidable challenge in the field of integrated photonics still remains for combining the strengths of different optical materials in one hybrid integrated platform. Silicon carbide is a material of great interest because of its high refractive index, strong second-and third-order nonlinearities, and broad transparency window in the visible and near-infrared range. However, integrating silicon carbide (SiC) has been difficult, and current approaches rely on transfer bonding techniques that are timeconsuming, expensive, and lacking precision in layer thickness. Here, we demonstrate high-index amorphous silicon carbide (a-SiC) films deposited at 150 °C and verify the high performance of the platform by fabricating standard photonic waveguides and ring resonators. The intrinsic quality factors of single-mode ring resonators were in the range of Q int = (4.7−5.7) × 10 5 corresponding to optical losses between 0.78 and 1.06 dB/cm. We then demonstrate the potential of this platform for future heterogeneous integration with ultralow-loss thin SiN and LiNbO 3 platforms.

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Section: Introductionsupporting

confidence: 80%

High-Quality Amorphous Silicon Carbide for Hybrid Photonic Integration Deposited at a Low Temperature

Lopez-Rodriguez,

van der Kolk,

Aggarwal

et al. 2023

ACS Photonics

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“…Moreover, the Q factor is higher for wafers utilising LPCVD Si 3 N 4 , attributable to reduced internal losses and diminished top-surface roughness. 4 The model assessment of the Q factor is displayed in Figure 13. The model assessment employing equation 5, in conjunction with the simulations of the transmission coefficient and group index, demonstrates significant success on a quantitative level.…”

Section: Probing Systemmentioning

confidence: 99%

“…3 Furthermore, the inherent compatibility of Si 3 N 4 platforms with CMOS processes in foundries paves the way for the highly stable and precise fabrication of resonator structures, thus enhancing their overall performance and reliability. 4 A ring resonator is primarily composed of an optical waveguide contoured into a loop, in conjunction with a coupling mechanism that grants access to the loop. This specific loop configuration enables the circulation of waves, which, upon accumulating a phase shift equivalent to a multiple of 2π, experience constructive interference, consequently inducing resonance within the cavity.…”

Section: Introductionmentioning

confidence: 99%

Design optimization of silicon nitride-based micro-ring resonator systems in a CMOS mass production environment

Hinum-Wagner,

Buchberger,

Schmidt

et al. 2023

Integrated Optics: Design, Devices, Systems and Applications VII

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Micro-ring resonators (MRR) are basic photonic components, which serve as crucial building blocks for a variety of devices, e.g. integrated sensors, external cavity lasers, and high speed photonic data transmitters. Silicon nitride photonic platforms are particularly appealing in this field o f a pplication, s ince t his w aveguide material enables on-chip photonic circuitry with (ultra-) low losses in the NIR as well as across the whole visible spectral range. In this contribution we investigate key performance properties of MRRs in the wavelength range around 850 nm, such as free spectral range (FSR), quality factor (Q factor) and extinction ratio. We systematically investigate a large parameter space given by the MRR radii, coupling gaps between ring and bus waveguide, as well as waveguide width. Furthermore, we compare key properties such as the Q factor between low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD) Si 3 N 4 platforms and find enhanced values for LPCVD ring resonators reaching nearly a Q factor of 10 6 .The fabrication is carried out with standard CMOS foundry equipment, utilizing photolithography and reactive ion etching on 250 nm thick silicon nitride films. A s c ladding m aterial, h igh d ensity P ECVD s ilicon o xide i s d eposited p rior t o the waveguide onto bare silicon and a sputtered oxide serves as upper cladding. With this process toolbox full CMOS backend compatibility is achieved when considering only PECVD Si 3 N 4 waveguide material. In terms of manufacturability, special focus is put on the die-to-die as well as on wafer-to-wafer variability of the performance parameters, which is crucial when considering mass production of MRR devices. Finally, the experimental findings are compared to finite difference time domain (FDTD) simulations of the MRR circuits revealing excellent agreement when considering the manufacturing variability.

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“…Two predominant sources contribute to these losses: surfaceroughness-induced scattering and absorption losses. 3,4 Surface roughness, an inherent characteristic of waveguide materials and the associated processing steps, is invariably introduced during the intricate deposition processes, specifically during etching and lithographic stages. This surface irregularity, as well as absorption centres in the material, causes attenuation of the guided light waves, culminating in energy loss and a subsequent reduction in the efficiency of the overall photonics system.…”

Section: Introductionmentioning

confidence: 99%

Ab-initio modeling of bend-losses in silicon nitride waveguides from visible to near-infrared

Hinum-Wagner,

Hörmann,

Sattelkow

et al. 2023

Optical Modeling and Performance Predictions XIII

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Integrated photonics features applications in high-speed telecommunication, computing, and sensing. These devices are ultimately limited by the optical loss occurring in the waveguide structures. One of its primary sources is surface-roughness-induced scattering and bend-losses. Surface roughness is unavoidably introduced during deposition, mainly during etching and lithographic steps. In photonic integrated circuits, tight bends enable a compact footprint yet increase the mode mismatch loss , radiation loss and scattering loss. Previously, the bend losses were estimated from a parametric model. However, it lacks flexibility w.r.t. the waveguide platform. We apply a recently developed model of the surface-roughness-induced scattering in guided-mode systems to substantiate the dependence of the scattering loss on the bend-radius for waveguides based on a silicon nitride platform. The model incorporates the surface roughness via its autocorrelation. Further, it inherently considers the overlap of the modes with the roughness. As waveguide material, we used both plasma-enhanced CVD silicon nitride as a low-temperature, back-end-compatible process, and low-pressure CVD silicon nitride, as a high-temperature frontend process. As bottom and top cladding, we deposited high-density plasma (HDP) and sputtered silicon oxide, respectively. The latter offers flexibility to adapt the platform for sensing purposes. We evaluate different waveguide widths, bend radii, and wavelengths in the visible and near-infrared ranges. We set the observed propagation losses into context with estimated absorption, scattering, and mode-overlap loss sources and point to their shifting importance at the measured wavelengths. We believe that this model allows to increase our knowledge about the various aspects of loss in guided mode systems and predict the propagation loss based on foregoing absorption and roughness measurements.

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Ultra‐Low‐Loss Silicon Nitride Photonics Based on Deposited Films Compatible with Foundries

Cited by 22 publications

References 39 publications

High-Quality Amorphous Silicon Carbide for Hybrid Photonic Integration Deposited at a Low Temperature

High-Quality Amorphous Silicon Carbide for Hybrid Photonic Integration Deposited at a Low Temperature

Design optimization of silicon nitride-based micro-ring resonator systems in a CMOS mass production environment

Ab-initio modeling of bend-losses in silicon nitride waveguides from visible to near-infrared

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