Observation of nanometer silicon clusters in the hot-filament CVD process

Currents of 0.2-5 mu A were measured in the hot filament CVD chamber for deposition of silicon. In such a highly ionizing atmosphere with the appreciable supersaturation for precipitation of silicon, it is highly probable that the charged clusters should be formed in the gas phase by ion-induced or photo-induced nucleation. The predicted nanometer silicon clusters were observed by TEM on a carbon membrane, which was placed in the hot-filament CVD chamber in the Si-Cl-H system. The clusters for the filament temperatures of 1800 and 1600 degrees C were similar to 2 nm and 5-7 nm, respectively. The film grown by the deposition of these clusters did not show any identity of the individual clusters, making the film indistinguishable from that grown by the atomic unit. In the case of the halogen lamp heating instead of the hot filament, however, the film consists of the large clusters of similar to 50 nm and the morphology is similar to the cauliflower structure. The morphological difference between the two heating sources was explained by Fujita's concert of the magic size. (C) 1999 Elsevier Science B.V. All rights reserved.