Dresden 2003 – scientific programme

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DS: Dünne Schichten

DS 5: Verfahren zur Schichtherstellung II

DS 5.1: Talk

Monday, March 24, 2003, 10:15–10:30, GER/38

Low-temperature Si epitaxy by electron-cyclotron resonance chemical vapor deposition — •Björn Rau, Burkhardt Selle, Ina Sieber, Stefan Gall, and Walther Fuhs — Hahn-Meitner-Institut Berlin, Abt. Silizium-Photovoltaik, Kekuléstr. 5, D-12489 Berlin

We report on a study of homo-epitaxial growth of Si absorber layers at low temperatures using electron-cyclotron resonance chemical vapor deposition (ECR-CVD). The background of this research is the development of low-temperature deposition techniques for thin-film solar cells on large-grained polycrystalline Si. The films were grown at temperatures between 420 ^oC and 560 ^oC on mono- and polycrystalline Si-wafers.

Both substrate temperature and orientation have a pronounced influence on the structural quality. At 510 ^oC good epitaxial growth was observed on Si(100) substrates with growth rates of 15 nm/min up to a film thicknesses of 2.5 µm. Below 480 ^oC the disorder in the films increases sicnificantly with decreasing temperature starting right at the interface. On Si(111)-wafers films grew always microcrystalline. Using polycrystalline substrates the quality of the films is related to the orientation of the particular grain. We observed different degrees of disorder from excellent epitaxy up to pure microcrystalline growth. With increasing thickness, the epitaxial films show locally high defective regions but no evidence of an amorphous phase in the films has been observed. Therefore the classical break down of epitaxy after a critical thickness was not seen up to 2.5 µm.