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NH3-free PECVD silicon nitride for photonic applications

NH3-free PECVD silicon nitride for photonic applications
NH3-free PECVD silicon nitride for photonic applications
Silicon Photonics has open the possibility of developing multilayer platforms based on complementary metal-oxide semiconductors compatible materials that have the potential to provide the density of integration required to fabricate complex photonic circuits. Amongst these materials, silicon nitride (SiN) has drawn attention due to its fabrication flexibility and advantageous intrinsic properties that can be tailored to fulfil the requirements of different linear and non-linear photonic applications covering the ultra-violet to mid-infrared wavelengths. Yet, the fabrication techniques typically used to grow SiN layers rely on processing temperatures > 400 C to obtain low propagation losses, which deem them inappropriate for multilayer integration. This thesis presents a systematic investigation that provided a comprehensive knowledge of a deposition method based on an NH3-free plasma enhanced chemical vapour deposition recipe that allows the fabrication of low-loss silicon nitride layers at temperatures < 400 C. The results of this study showed that the properties of the studied SiN layers depend mostly on their N/Si ratio, which is in fact one of the only properties that can be directly tuned with the deposition parameters. These observations provided a framework to optimise the propagation losses and optical properties of the layers in order to develop three platforms intended for specific photonic applications. The first one comprises 300nm stoichiometric SiN layers with refractive index (n) of 2 that enable the fabrication of photonic devices with propagation losses < 1 dB/cm at l = 1310nm and < 1:5 dB/cm at l = 1550 nm, which are good for applications that require efficient routing of optical signals. The second one consists on 600nm N-rich layers (n = 1.92) that allow fabricating both devices with propagation losses < 1 dB/cm at l = 1310 nm, apt for polarisation independent operation and coarse wavelength division multiplexing devices with cross-talk < 20 dB and low insertion losses. Finally, the last platform consisted of suspended Si-rich layers (n = 2.54) that permits the demonstration of photonic crystal cavities with Q factors as high as 122 000 and photonic crystal waveguides capable of operating in the slow-light regime. Hopefully, the demonstration of these platforms will stimulate the development of more complex SiN devices for multilayer routing, wavelength division multiplexing applications and non-linear integrated photonics in the future.
University of Southampton
Domínguez Bucio, Thalía
83b57799-c566-473c-9b53-92e9c50b4287
Domínguez Bucio, Thalía
83b57799-c566-473c-9b53-92e9c50b4287
Mashanovich, Goran
c806e262-af80-4836-b96f-319425060051
Gardes, Frederic
7a49fc6d-dade-4099-b016-c60737cb5bb2

Domínguez Bucio, Thalía (2018) NH3-free PECVD silicon nitride for photonic applications. University of Southampton, Doctoral Thesis, 288pp.

Record type: Thesis (Doctoral)

Abstract

Silicon Photonics has open the possibility of developing multilayer platforms based on complementary metal-oxide semiconductors compatible materials that have the potential to provide the density of integration required to fabricate complex photonic circuits. Amongst these materials, silicon nitride (SiN) has drawn attention due to its fabrication flexibility and advantageous intrinsic properties that can be tailored to fulfil the requirements of different linear and non-linear photonic applications covering the ultra-violet to mid-infrared wavelengths. Yet, the fabrication techniques typically used to grow SiN layers rely on processing temperatures > 400 C to obtain low propagation losses, which deem them inappropriate for multilayer integration. This thesis presents a systematic investigation that provided a comprehensive knowledge of a deposition method based on an NH3-free plasma enhanced chemical vapour deposition recipe that allows the fabrication of low-loss silicon nitride layers at temperatures < 400 C. The results of this study showed that the properties of the studied SiN layers depend mostly on their N/Si ratio, which is in fact one of the only properties that can be directly tuned with the deposition parameters. These observations provided a framework to optimise the propagation losses and optical properties of the layers in order to develop three platforms intended for specific photonic applications. The first one comprises 300nm stoichiometric SiN layers with refractive index (n) of 2 that enable the fabrication of photonic devices with propagation losses < 1 dB/cm at l = 1310nm and < 1:5 dB/cm at l = 1550 nm, which are good for applications that require efficient routing of optical signals. The second one consists on 600nm N-rich layers (n = 1.92) that allow fabricating both devices with propagation losses < 1 dB/cm at l = 1310 nm, apt for polarisation independent operation and coarse wavelength division multiplexing devices with cross-talk < 20 dB and low insertion losses. Finally, the last platform consisted of suspended Si-rich layers (n = 2.54) that permits the demonstration of photonic crystal cavities with Q factors as high as 122 000 and photonic crystal waveguides capable of operating in the slow-light regime. Hopefully, the demonstration of these platforms will stimulate the development of more complex SiN devices for multilayer routing, wavelength division multiplexing applications and non-linear integrated photonics in the future.

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Final thesis - Version of Record
Available under License University of Southampton Thesis Licence.
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Published date: June 2018

Identifiers

Local EPrints ID: 422874
URI: http://eprints.soton.ac.uk/id/eprint/422874
PURE UUID: 461f266a-8980-4674-b775-a2f22ff268d0
ORCID for Thalía Domínguez Bucio: ORCID iD orcid.org/0000-0002-3664-1403
ORCID for Frederic Gardes: ORCID iD orcid.org/0000-0003-1400-3272

Catalogue record

Date deposited: 07 Aug 2018 16:30
Last modified: 16 Mar 2024 06:57

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