Process transfer of a-SixC1-x passivation layers from a laboratorytype to an industrial in-line PECVD reactor

Abstract

We report the successful transfer of passivating, intrinsic a-Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> :H layers from a laboratory batch-type to an industrial in-line plasma-enhanced chemical vapour deposition (PECVD) reactor. In both cases silane (SiH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> ) and methane (CH <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> ) are used as precursor gases and the plasma energy is provided by a high frequency (13.65 MHz) as well as by a microwave (2.45 GHz) generator. Intensive process parameters such as temperature (350–400°C) and pressure (0.3–0.4 mbar) could be directly transferred from the lab to the industrial system whereas power and gas composition had to be adjusted carefully to the different dimensions and geometry of the in-line reactor. By means of a statistical design of the experiments a parameter range for passivating a-Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> layers could be found resulting in surface recombination velocities as low as S ≪ 10 cm/s. These values could be achieved without applying any wetchemical step to the silicon samples as the cleaning of the surface was performed in-situ in the plasma chamber. The deposition rate is 100 nm/min and therefore an order of magnitude higher than in our laboratory-type system. Fourier transform infrared spectroscopy (FT-IR) measurements performed on the in-line deposited a-Si <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</inf> layers reveal an elevated carbon content compared to their counterparts originating from our static laboratory PECVD reactor.