A 200 mm Wafer-Scale Al2O3 Photonics Waveguide Technology for UV and Visible Applications

Low-loss, UV wavelength compatible Al₂O₃ photonic waveguides have been fabricated in a 200 mm CMOS pilot line. The Al₂O₃ waveguide layer optical properties and roughness were characterized by ellipsometry and AFM, respectively. Optical losses of the slab mode in the waveguide layer were studied by prism coupling. SiO₂-cladded Al₂O₃ waveguides were patterned on 200 mm wafers and propagation losses were measured at 266, 360, 450, 532 and 638 nm wavelengths. Wafer-level measurements for 360–638 nm show an average propagation loss below 0.6 dB/cm, while die-level measurements for 266 nm yield average propagation losses between 4.3 and 14.7 dB/cm. To study the dependence of the wave propagation on processing variations, large sets of Mach-Zehnder interferometers with varying arm lengths were measured at a wavelength of 360 nm, and the coherence length of the standard 450 nm wide and 110 nm high Al₂O₃ waveguide was calculated to be longer than 2.2 mm.