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Decreasing Interface Defect Densities via Silicon Oxide Passivation at Temperatures Below 450 °C

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journal contribution
posted on 2020-09-30, 20:43 authored by Zahra Jahanshah Rad, Juha-Pekka Lehtiö, Iris Mack, Kawa Rosta, Kexun Chen, Ville Vähänissi, Marko Punkkinen, Risto Punkkinen, Hannu-Pekka Hedman, Andrei Pavlov, Mikhail Kuzmin, Hele Savin, Pekka Laukkanen, Kalevi Kokko
Low-temperature (LT) passivation methods (<450 °C) for decreasing defect densities in the material combination of silica (SiOx) and silicon (Si) are relevant to develop diverse technologies (e.g., electronics, photonics, medicine), where defects of SiOx/Si cause losses and malfunctions. Many device structures contain the SiOx/Si interface(s), of which defect densities cannot be decreased by the traditional, beneficial high temperature treatment (>700 °C). Therefore, the LT passivation of SiOx/Si has long been a research topic to improve application performance. Here, we demonstrate that an LT (<450 °C) ultrahigh-vacuum (UHV) treatment is a potential method that can be combined with current state-of-the-art processes in a scalable way, to decrease the defect densities at the SiOx/Si interfaces. The studied LT-UHV approach includes a combination of wet chemistry followed by UHV-based heating and preoxidation of silicon surfaces. The controlled oxidation during the LT-UHV treatment is found to provide an until now unreported crystalline Si oxide phase. This crystalline SiOx phase can explain the observed decrease in the defect density by half. Furthermore, the LT-UHV treatment can be applied in a complementary, post-treatment way to ready components to decrease electrical losses. The LT-UHV treatment has been found to decrease the detector leakage current by a factor of 2.