Ion implantation of silicon and germanium at room temperature. Analysis by means of 1.0-MeV helium ion scattering

Abstract

The orientation dependence of the backscattered yield of 1.0-MeV helium ions has been used to investigate the lattice characteristics of silicon and germanium implanted at room temperature with 40-keV heavy ions (Ga, As, Sb, In, P). The method gives directly the number of substrate atoms displaced from their lattice sites by more than the Thomas–Fermi screening distance (≈ 0.2 Å) and also the location of the implanted atoms.Each heavy ion is found to displace several thousand lattice atoms in a localized region around its track. At doses where the individual disordered regions do not overlap (~1013 ions/cm2, or less), the silicon lattice reorders at 260 °C and the germanium lattice at 180 °C. At doses greater than ~1014 ions/cm2, a completely amorphous layer is formed in both silicon and germanium. During annealing, the reordering of the lattice is initiated at the interface between the amorphous region and the underlying crystal. The reordering of this amorphous layer occurs at significantly higher temperatures (570 °C in Si and 380 °C in germanium) than those required for the isolated disordered regions. At doses much greater than 1015/cm2, even higher anneal temperatures are required.Following a room-temperature implantation, each implanted atom is embedded in a highly disordered region (at least, for doses > 1014/cm2) and consequently the backscattered spectra from these atoms do not show orientation effects. As the lattice reorders during annealing, the number of implanted atoms lying along the [Formula: see text] lattice row increases. Following anneal, ~75% of the As atoms and ~90% of the Sb atoms are found on substitutional sites in silicon, while in germanium, ~80% of the In atoms are found on substitutional sites. Annealing to higher temperatures (700–900 °C in the case of silicon) often causes the number of substitutional atoms to decrease again, owing to the effect of internal precipitation or diffusion to the surface.

Micro-Raman and Spreading Resistance Analysis on Beveled Implanted Germanium for Layer Transfer Applications

“…Radiation damage is known to cause donor 2 and acceptor 3 states in the bandgap of many semiconductors, through the formation of vacancies and interstitials, which, on annealing, interact with hydrogen, oxygen, or dopant atoms already present in the lattice structure. The published literature on the annealing behavior of the damaged and amorphous Ge after ion implantation is mainly limited to the heavy ions ͑e.g., Ga, As, Sb, In, P, 4 Si, and Ge 5,6 ͒ at medium 6,7 ͑10 14 atoms/cm 2 ͒ to low ͑10 12 atoms/cm 2 ͒ fluences. In all the cases the maximum annealing required for full recrystallization was 500°C for 30 min.…”

On the Mechanisms of Hydrogen Implantation Induced Silicon Surface Layer Cleavage

“…This is in good agreement with the XTEM observations. Previous studies have shown, that recrystallization of an amorphous silicon layer by solid phase epitaxy is achievable at the present anneal temperature [149,150]. Due to the high concentration of hydrogen in the implantation zone and its interaction with lattice defects, which prohibits recrystallization of the silicon, only the shallow part of the amorphous layer recrystallized.…”

Model of amorphous-silicon-layer regrowth

“…The thickness of this layer is of the nrder of 2RP, where RP is the average projected range of the incident ions. 4 There are several variables that affect the ion dose required to form an amorphous layer. The ion species is critical 5 since heavy ions cause amorphitization more readily.…”