Effective Use of UV-Ozone Oxide in Silicon Solar Cell Applications

It is long recognized that high-quality surface cleaning is critical for an increased performance of solar cells and semiconductor devices. In this contribution, the effectiveness of UV-ozone cleaning by comparing it against the industry standard RCAand UV-assisted deionized water (DI-O-3) techniques has been demonstrated. UV-ozone cleaning results in an effective surface passivation quality that is comparable to both RCAand DI-O-3 cleans, realizing a recombination current density (J(0)) of 7 fA cm(-2) as compared to 5 and 8 fA cm(-2) for RCAand DI-O-3 cleans, respectively. Repeating the UV-ozone clean on samples (i.e., growing of UV-ozone oxide and stripping it in HF) more than twice results in a cleaning efficiency that is nearly identical to RCAclean. Based on a high resolution transmission electron microscopy analysis, the post-annealed thickness of the UV-ozone oxide layer was found to reduce in comparison to the pre-annealed condition. This is likely due to oxygen diffusion from the UV-ozone oxide layer into the overlaying AlOx layer. Additionally, it has been found that a reduction in UV-ozone oxide deposition time to just 5 min still provides a comparable cleaning efficiency to the RCAclean, and also results in good passivation quality (5-8 fA cm(-2)) on both planar and textured samples.