The Use of Seed Layers in Hot Wire Chemical Vapor Deposition of Microcrystalline Silicon Films

Abstract

AbstractThe effect of thin seed layers on the subsequent growth of thick, high growth rate bulk μc-Si is investigated by XRD, SEM and cross sectional TEM. All layers were deposited by hotwire chemical vapor deposition (HWCVD). When the seed layer as observed by XRD is highly crystalline, made by using high H2 dilution (H2:SiH4 100:1), the amorphous incubation layer typical of μc-Si growth is virtually eliminated. Furthermore, with this seed layer, bulk layer deposition conditions that would otherwise produce highly amorphous material enable a composite film with significant crystallinity. When the seed layer is predominantly amorphous, made using a much lower H2 dilution (10:1), there is evidence that very small crystallites, undetected by XRD, still facilitate immediate nucleation and enable the formation of larger grains in the subsequent bulk layer. In concurrence with other HWCVD results, lowering the filament temperature results in significant improvements in film compactness, photoresponse and grain size, while maintaining significant crystallinity. Such films have been incorporated into high deposition rate solar cells.