Germanium fin structure optimization for future MugFET and FinFET applications

(100) germanium wafers were patterned by e-beam lithography with various exposure doses, in combination with dry etch, resulting in fin structures with widths in the range of 20-150 nm with a high aspect ratio, running in either the [100] or [110] direction. Fins were also subjected to various anneals in N ₂ to examine germanium desorption but little or no size reduction was observed for typical dopant activation thermal budgets. Other samples received a phosphorus implant (at 7°) that partially amorphized the structures. The amorphous depth was 120 nm. Subsequently a 400 °C 3 min furnace anneal in N₂ recrystallized the wide fins completely, leading to the formation of various defects, including twin boundaries, small localized defects, and stacking faults. Recrystallization was retarded in narrow fins as was reported in silicon fins.