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Silicon surface passivation by ultrathin Al 2 O 3 films synthesized by thermal and plasma atomic layer deposition
Author(s) -
Dingemans G.,
Seguin R.,
Engelhart P.,
Sanden M. C. M. van de,
Kessels W. M. M.
Publication year - 2010
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.200903334
Subject(s) - passivation , atomic layer deposition , thermal stability , plasma , annealing (glass) , silicon , materials science , analytical chemistry (journal) , layer (electronics) , thermal , surface modification , chemistry , nanotechnology , optoelectronics , metallurgy , physics , quantum mechanics , organic chemistry , chromatography , meteorology
In this Letter, we report that both thermal atomic layer deposition (ALD) with H 2 O, and plasma ALD with an O 2 plasma, can be used to deposit Al 2 O 3 for a high level of surface passivation of crystalline silicon (c‐Si). For 3.5 Ω cm n‐type c‐Si, plasma ALD Al 2 O 3 resulted in ultralow surface recombination velocities of S eff < 0.8 cm/s. Thermal ALD Al 2 O 3 also showed an excellent passivation level, with S eff < 2.5 cm/s. In contrast to plasma ALD Al 2 O 3 , thermal ALD Al 2 O 3 provides some surface passivation in the as‐deposited state, although annealing is required to activate it to the full extent. For thermal ALD, the optimal temperature for this anneal was found to be slightly lower, ∼375 °C, than for plasma ALD Al 2 O 3 , ∼425 °C. The minimal Al 2 O 3 thickness without compromising the passivation properties was 5 nm for plasma ALD Al 2 O 3 , whereas for thermal ALD, films >10 nm were required. Thermal stability against a high temperature firing step was demonstrated for ultrathin thermal and plasma ALD Al 2 O 3 films of 5 nm by S eff < 9.2 and < 6.5 cm/s, respectively. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)