Abstract
Thin, flexible silicon crystals are starting up applications such as light-weighted flexible solar cells, SOI, flexible IC chips, 3D ICs imagers and 3D CMOS imagers on the demand of high performance with low cost. Kerfless wafering technology by direct conversion of source gases into mono-crystalline wafers on reusable substrates is highly cost-effective and feedstock-effective route to cheap wafers with the thickness down to several microns. Here we show a prototype for direct conversion of silicon source gases to wafers by using the substrate with protruded seeds. A reliable and controllable method of wafer-scaled preparation of protruded seed patterns has been developed by filling liquid wax into a rod array as the mask for the selective removal of oxide layer on the rod head. Selectively epitaxial growth is performed on the protruded seeds, and the voidless film is formed by the merging of neighboring seeds through growing. And structured hollows are formed between the grown film and the substrate, which would offer the transferability of the grown film and the reusability of the protruded seeds.
Highlights
Silicon is the dominant semiconductor material in the modern electronic and photovoltaic industries
A porous silicon bilayer was built by anodization of traditional Si mono-crystal wafers in HF solution with platinum as cathode; the pores on the surface were sealed by hydrogen annealing, forming a thin quasi-mono-crystal template for subsequent epitaxial growth of silicon; the unsealed porous layer was used as a sacrificial layer when the grown wafer was lifted off; and the thickness of grown wafer was controlled just by growth duration, available from several microns to hundreds of microns
We demonstrate a prototype using patterned protruded seeds to epitaxially grow silicon films,[21] intending to form uniformly hollows between the grown film and the mother substrate by the seed supporting structures, in this way, one approach might be achieved that the grown film / wafer could be lifted off without any sacrificial layer and the seeded mother substrate could be reused without any rebuilding steps in liquid
Summary
Silicon is the dominant semiconductor material in the modern electronic and photovoltaic industries. Thin flexible silicon crystals are spurring applications such as high efficient light-weight and flexible solar cells,[8,9,10,11,16,17] SOI,[12] flexible IC chips,[13] monolithic 3D ICs and CMOS imager,[14,15] and flexible transistors.[18] It is rather challenging for the epitaxial technology based on porous silicon layers to avoid metallic contaminants from the electrolyte,[8] and the reuse of mother substrates is limited by the re-creating step of the porous double layer in electrolyte solution.[19,20]. We demonstrate a prototype using patterned protruded seeds to epitaxially grow silicon films,[21] intending to form uniformly hollows between the grown film and the mother substrate by the seed supporting structures, in this way, one approach might be achieved that the grown film / wafer could be lifted off without any sacrificial layer and the seeded mother substrate could be reused without any rebuilding steps in liquid
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