Abstract
We present interlayer slope waveguides, designed to guide light from one level to another in a multi-layer silicon photonics platform. The waveguide is fabricated from hydrogenated amorphous silicon (a-Si:H) film, deposited using hot-wire chemical vapor deposition (HWCVD) at a temperature of 230°C. The interlayer slope waveguide is comprises of a lower level input waveguide and an upper level output waveguide, connected by a waveguide on a slope, with vertical separation to isolate other crossing waveguides. Measured loss of 0.17 dB/slope was obtained for waveguide dimensions of 600 nm waveguide width (w) and 400 nm core thickness (h) at a wavelength of 1550 nm and for transverse electric (TE) mode polarization.
Highlights
Wafer space on an optical chip is seen as the challenge to bring silicon photonics (SiP) to mass market
The device is not restricted to any propagation modes, transverse electric (TE) mode polarization at a wavelength of 1550 nm is used for our device characterization as it is commonly used for silicon-on-insulator (SOI) platforms in silicon photonic integrated circuits (Si-PICs) due to its use as a standard telecom wavelength [12]
All fabrication processes were regulated below 400°C for Back End of Line (BEOL) compatibility
Summary
Wafer space on an optical chip is seen as the challenge to bring silicon photonics (SiP) to mass market. Several groups such as Selvaraja et al [14], Zhu et al [15], Furuya et al [16] and Takei et al [17] have reported high-quality plasma enhanced chemical vapour deposition (PECVD) a-Si:H film These groups have demonstrated submicron sized waveguide structure with propagation losses between 0.6 dB/cm and 3.45 dB/cm, which is fundamental for the realization of 3D interconnect [18]. The main advantage of using the HWCVD tool in our work over plasma-enhanced chemical vapour deposition (PECVD) is the effective dissociation of the precursor gas, i.e., silane (SiH4), into atomic silicon (Si) and hydrogen (H2) molecules, by the hot filaments which reduces film stress due to the absence of plasma ion bombardment [19] This allows high quality HWCVD aSi:H thin film to be attainable at low temperature below 400°C for Back End of Line (BEOL) process compatibility [20]. The device is not restricted to any propagation modes, transverse electric (TE) mode polarization at a wavelength of 1550 nm is used for our device characterization as it is commonly used for silicon-on-insulator (SOI) platforms in silicon photonic integrated circuits (Si-PICs) due to its use as a standard telecom wavelength [12]
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