Effective Antireflection and Surface Passivation of Silicon Using a SiO2/a-TiOx Film Stack

This paper reports an effective and industrially relevant passivation and antireflection film stack featuring a 10 nm silicon dioxide (SiO2) film followed by a approximate to 65 nm amorphous titanium oxide (a-TiOx) film. This film stack has equivalent optical performance to a single-layer silicon nitride (SiNx) antireflection coating (ARC) for unencapsulated cells, and slightly better performance for encapsulated cells (approximate to 0.2 mA center dot cm(- 2) increase). The field effect passivation properties of the SiO2/a-TiOx film stack have been modified extrinsically after the film deposition to demonstrate surface recombination velocities below 1.2 cm/s in a 1 Omega center dot cm n-type silicon wafer. Finally, the TiOx films have been deposited using an inline atmospheric pressure chemical vapor deposition (APCVD) system at temperatures below 350 degrees C, thus demonstrating this film stack offers both better passivation and optical performance, as well as a potentially lower manufacturing cost compared to SiNx, due to the use of APCVD rather than plasma-enhanced chemical vapor deposition. Simulations indicate further gains in terms of optical performance (approximate to 0.3 mA center dot cm(- 2) increase compared to SiNx - encapsulated case) may be possible using a double-layer ARC featuring a polycrystalline TiOx film followed by an aluminum oxide (AlOx). However, potential contamination from the APCVD may pose a risk to maintaining high bulk carrier lifetimes.