Influence of RTA and LTA on the Optical Propagation Loss in Polycrystalline Silicon Wire Waveguides

To provide flexibility in implementing polySi devices in Si optoelectronic integrated circuits, polySi wire waveguides were fabricated with various low thermal budget solid-phase crystallization (SPC) approaches, i.e., spike rapid thermal annealing (RTA) at 1050°C for < 1 s, low-temperature annealing (LTA) at 600°C for 15 h, or a combination of both with different sequences. The approach of first LTA and then RTA reaches a relatively low optical loss at 1550 nm: ~ 9.8 dB/cm in 300-nm-wide polySi waveguides after an additional forming gas annealing at 420°C to passivate the dangling bonds, close to that fabricated with the conventional high thermal budget SPC.