Investigation of Wide Process Temperature Window for Amorphous Silicon Suboxide Thin-Film Passivation Deposited by Inductively Coupled PECVD

Hydrogenated intrinsic amorphous silicon suboxide thin films deposited onto c-Si wafers by decomposing hydrogen, silane, and carbon dioxide in an industrial remote inductively coupled plasma tool are studied. Compared with intrinsic amorphous silicon deposited in the same tool, this material displays an improved process temperature window and excellent surface passivation quality, which is important for industrialization. The wide process window of over 200 °C (100 to 350 °C) mainly results from the slow depletion of H atoms at elevated temperature due to a suppressed epitaxial growth, whereas the excellent passivation quality is due to a much higher H content in the film compared with amorphous silicon. The temperature stability is further supported by a study using a high-resolution transmission electron microscopy. Under the optimal condition, the amorphous silicon suboxide demonstrates an effective minority carrier lifetime of over 4.7 ms on planar n-type 1-Ω · cm Czochralski silicon wafers, which is equivalent to an effective surface recombination velocity of less than 1.7 cm/s, and an implied open-circuit voltage of 741 mV.