Fabrication of silicon nitride waveguides for visible-light using PECVD: a study of the effect of plasma frequency on optical properties

Abstract

This paper presents work aimed at optimizing the fabrication of silicon nitride Si(x)N(y) thin-film visible-light planar waveguides using plasma-enhanced chemical vapour deposition (PECVD). The effects of plasma frequency, precursor gas ratio, and thermal annealing in relation to waveguide optical properties (refractive index, propagation losses) are studied. Experimental results over a wide range of precursor gas ratios show convincingly that waveguides fabricated using low-frequency PECVD have lower propagation losses in the visible range compared to waveguides of equal refractive index fabricated with high-frequency PECVD.

Optical properties of high refractive index thin films processed at low-temperature

“…Transmittance spectra and ellipsometry measurements were conducted over the 400-900 nm spectral range. Thickness and refractive index of the films were calculated using the Tauc-Lorentz model fitted to the ellipsometry data [17]. In order to characterise the propagation losses, thin films were deposited on silicon substrates with a thick optical isolation layer.…”

Near-Infrared Grating Couplers for Silicon Nitride Photonic Wires

“…GC-based PICs will help in realizing efficient and easy-to-use integrated spectrometers and sensors. Si 3 N 4 is a versatile HIC platform for its transparency at both visible and infrared wavelengths [7]- [9]. Besides it is compatible with the well established complementary-metal-oxide-semiconductor (CMOS) process technology thereby enabling low-cost photonic devices much like in silicon photonics.…”

Integrating Micro-Photonic Systems and MOEMS into Standard Silicon CMOS Integrated Circuitry

“…The inter-metallic oxide, positioned between metallic layers, are CVD plasma deposited and mainly used as electrical isolation between the metal layers. Literature surveys (Beals et al , 2008, Gorin et al, 2008 show that, even so, these layers are porous, they offer suitable propagation for the longer mid infra-red wavelengths, where structural defects, such as porosity, grain boundaries and side wall scattering due to roughness play a lesser role . The metallic layers bonding to the oxide inter-metallic oxide layers can be used as effective reflectors or optical confinement layers.…”

“…A recent analysis shows that both, silicon nitride and Si oxi-nitride, transmitting radiation at low loss between 650 and 850 nm (Daldossa et al, 2004;Gorin et al, 2008). Both, Si O x N y and Si x N y possess high refractive indices of 1.6 -1.95 and 2.2 -2.4 respectively, against a background of available SiO 2 as cladding or background layers in CMOS silicon .…”

“…The results were published by Daldossa et al , 2004. The second curve corresponds to a low frequency deposition process as recently developed by Gorin et al (2008). The third curve corresponds to a special low frequency process followed by a low temperature "defect curing" technique as developed by Gorin et al This process offers superb low loss characteristics.…”