Fig. 1: SiN-assisted silicon photonic process for back-end-of-line integration of PCMs.

a Flowchart of the device fabrication process. b Measured transmission spectra of waveguides with different numbers of cascaded trenches. The inset shows the layout of the cascaded devices. c Waveguide loss introduced by the SiO₂ trench etching process assessed employing the cut-back method. The error bars corresponding to the standard deviation of multiple loss characterization results. d 3D schematic image of the device after fabrication.