The fluence effect in hydrogen-ion cleaving of silicon at the sub-100-nm scale

Abstract

The implementation at the sub-100-nm scale of ion cleaving requires ion beams of ∼5 keV/amu or less. The blistering efficiency in 5-keV H-ion-implanted and annealed Si has been found to peak and vanish in a narrow range of ion fluence of (1.5–3.5)×10¹⁶ H/cm². In order to understand this effect, the defect profiles in 5-keV H-irradiated Si were studied by Rutherford backscattering/channelling, while the Si-H bonding configurations during annealing were investigated by Raman scattering spectroscopy. Three types of defects play major roles: the ‘broad-band’ monohydride multivacancy complexes, the fully or partially passivated monovacancy VH_n, and H-terminated internal surfaces Si(100):H. Blister absence at high fluence is characterised by the persistence up to 550 °C of the Si(100):H structures, which are blister embryos that failed to coalesce and grow. Radiation-induced stresses and fracture toughening may play roles in inhibiting cleavage at high fluence; however, widening towards the surface of the zone of high H and defect concentration is the likely major factor.