Thermal stability of silicon surface passivation by APCVD Al 2O3

Verfasst von

Lachlan E. Black, Thomas Allen, Andres Cuevas, Keith R. McIntosh, Boris Veith, Jan Schmidt

Abstract

We investigate the thermal stability of silicon surface passivation provided by aluminium oxide (Al₂O₃) films deposited using atmospheric pressure chemical vapour deposition (APCVD) and fired in a belt furnace at a peak temperature of ~810 C. Firing stability is investigated for p- and n-type substrates as a function of Al₂O₃ film thickness both with and without a plasma-enhanced chemical vapour deposition (PECVD) SiN_x capping layer, and for boron-diffused surfaces with a ~10 nm Al₂O₃ film only. Excellent thermal stability of the passivation is demonstrated, with effective carrier lifetimes in n-type silicon wafers remaining stable or even improving after firing, and lifetimes in p-type wafers initially degrading slightly but recovering to above their initial values following ~10 min illumination by a halogen lamp at ~20 mW/cm ². Film thickness appears to be unimportant to stability, as does the presence of the capping layer. Surface recombination velocities of less than 3 cm/s for 1.35 Ω cm p-type and less than 2 cm/s for 1.2 Ω cm n-type substrates are measured after firing and illumination. The passivation of boron-diffused surfaces is also shown to improve slightly following firing, with a post-firing saturation current density of 42 fA/cm² on a diffusion with a sheet resistance of 100 Ω/□ and surface dopant concentration of ~1.3×10¹⁹ cm^-3. Capacitance-voltage (C-V) measurements show that short firing times result in an initial reduction of the interface defect density D_it and a slight increase of the negative insulator fixed charge density Q_f, while longer firing results in a substantial increase in both Q_f and D_it.

Details

Externe Organisation(en): Australian National University
PV Lighthouse
Institut für Solarenergieforschung GmbH (ISFH)
Typ: Artikel
Journal: Solar Energy Materials and Solar Cells
Band: 120
Seiten: 339-345
Anzahl der Seiten: 7
ISSN: 0927-0248
Publikationsdatum: 2014
Publikationsstatus: Veröffentlicht
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Elektronische, optische und magnetische Materialien, Erneuerbare Energien, Nachhaltigkeit und Umwelt, Oberflächen, Beschichtungen und Folien
Ziele für nachhaltige Entwicklung: SDG 7 - Erschwingliche und saubere Energie
Elektronische Version(en): https://doi.org/10.1016/j.solmat.2013.05.048 (Zugang: Geschlossen )
https://hdl.handle.net/1885/29928 (Zugang: Offen )