Formation of dendritic structures in thin silicon films on amorphous substrates by high intensity flash lamp annealing


Formation of dendritic structures in thin silicon films on amorphous substrates by high intensity flash lamp annealing

Endler, R.; Voelskow, M.; Schumann, T.; Gebel, T.; Liepack, H.; Kolitsch, A.; Skorupa, W.

Grain enlargement of the poly silicon is a key process to improve the electronic properties of microelectronic and photovoltaic devices. We report on lateral dendritic crystal growth in thin silicon films during liquid phase crystallization (LPC) induced by high intensity flash lamp irradiation (FLA). In a series of experiments first a 140 nm SiO2 film and then amorphous silicon of 100 nm thickness were deposited on 500µm thick (100) Si wafers. After that the top silicon film was ion implanted with carbon, first, with the aim to improve the wetting properties of the underlying silicon dioxide by the liquid silicon film during the LPC process. Secondly, due its different solubility in solid and liquid silicon, carbon is responsible for the formation of a laterally depending melting temperature inducing a lateral dendritic growth process. To prove in particular this influence of carbon on the wetting and crystallization process, the flash lamp irradiated structures were studied using XTEM analysis. The pulse annealing process was carried out using the commercial flash lamp annealing tool FLA-50RD of DTF-Technology. The installed set of standard Xenon flash lamps guarantees irradiation densities up to 150 J/cm2 at a pulse length of 20 ms on preheated substrates. As expected, depending on the carbon implantation conditions and the FLA energy densities, the films show, as a result, up to several hundred micrometers extended grains having the characteristic dendritic shape.

Keywords: Large grain silicon; Silicon layers on SiO2; Flash Lamp Annealing; Pulse melting; Dendritic crystal growth

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Publ.-Id: 17246