K.T. Short

Characterization of damage in ion implanted Ge

It has been observed that ion implantation into Ge at room temperature creates severe surface craters extending several thousand angstroms into the surface, and results in the incorporation of large quantities of C and O impurities (∼50 impurities/ion). This effect has a strong temperature dependence and essentially disappears for implantations performed at liquid nitrogen temperature. The systematics of this effect are presented, preliminary annealing results are cited, and possible mechanisms are discussed.

Impurity‐stimulated crystallization and diffusion in amorphous silicon

An amorphous‐to‐polycrystalline silicon transformation and concomitant In redistribution have been observed in In‐implanted silicon at temperatures well below those at which solid phase epitaxial growth or random crystallization is observed in undoped films. The process is extremely rapid and exhibits a strong dependence on both In concentration and temperature. It is proposed that the In redistribution and accompanying silicon crystallization are mediated by molten, In‐rich precipitates in amorphous silicon.

Channeling contrast microscopy: Application to semiconductor structures

The new technique is demonstrated for the imaging of semiconductor structures. The technique involves the use of a channeled 4He+ microbeam, scanned across the surface to provide a channeling‐contrast image of subsurface lattice disorder and atom location. The present arrangement provides a lateral resolution of ∼5 μm and an in‐depth resolution of ∼30 A. The technique is applied to the imaging of small, laser annealed regions on ion implanted silicon wafers.

Ion-beam-induced amorphization and dynamic annealing processes in silicon

Abstract Amorphization of (100) silicon has been studied during elevated-temperature implantation with keV heavy ions. The amorphization process is very sensitive to the balance between defect production and annihilation rates, the latter resulting from dynamic annealing during ion bombardment. Amorphous-phase production is shown to depend critically on the ion dose rate. Further measurements have indicated that the amorphous phase can be difficult to nucleate at elevated temperatures, requiring the presence of existing interfaces, surfaces or crystal defects to provide appropriate nucleation sites.

The annealing behavior of antimony implanted polycrystalline silicon

Dopant redistribution and sheet resistance of polycrystalline silicon films implanted with 100‐keV Sb+ ions to a dose of 1×1015 cm−2 or 3×1015 cm−2 have been investigated as a function of different annealing conditions. The correlation between Sb depth profiles, as measured by Rutherford backscattering, and sheet resistance provides considerable insight into the Sb doping behavior. In particular, low‐temperature (∼600 °C) short‐time (0.5 h) anneals resulted in good dopant activation without redistribution of the implanted Sb, whereas higher‐temperature anneals (≳900 °C) resulted in considerable redistribution. The sheet resistance of the films appeared to be controlled, to a large extent, by dopant segregation at grain boundaries and the fraction of the redistributed Sb within the grains.

Metastable solid solutions of antimony in (100) silicon

Abstract The annealing behaviour of high dose (1015−1016 cm−2) 80 keV Sb implants into (100) silicon has been investigated in detail, using transmission electron microscopy, Rutherford backscattering and channeling, 4 pt. probe (electrical) measurements and X-ray diffraction. The observed annealing behaviour of metastable Sb solid solutions is complex, involving crystal regrowth, along with several stages of diffusion and precipitation of Sb and of Si lattice defects. We speculate that Sb precipitation and relief of lattice strain is associated with movement of Si self-interstitials, which, in turn, precipitate out as visible defects.

The influence of electronic processes on the epitaxial regrowth rate in ion implanted silicon

Abstract High resolution Rutherford backscattering and channeling analysis has been used to investigate the effect of electrically active dopants on the solid phase epitaxial regrowth rate in silicon. Single and dual implants of In, Sn and Sb into (100) silicon have been employed, and annealing results show that both n-type (Sb) and p-type (In) dopants enhance the growth rate compared with undoped (Sn) and compensated (Sb+In) implants. We propose a model to explain these doping effects drawn from a recently proposed model to account for similar effects of doping on dislocation motion. The basic premise is that doping increases the concentration of (charged) kink-like nucleation sites at the amorphous-crystalline interface and that the regrowth velocity is proportional to the concentration of such growth sites.

Anomalous near-surface effects in room temperature implanted germanium

Abstract Rutherford backscattering and channeling analysis of high dose, room temperature implanted Ge has revealed an anomalous near-surface yield deficit. The effect is attributed to the absorption of oxygen and other light mass contaminants into a highly porous implanted layer upon exposure to air. The effect is not observed during liquid nitrogen implantation. Implant dose and species dependences, and the effect of annealing are examined.

Ion-Beam-Induced Damaging and Dynamic Annealing Processes in Silicon

We have employed high resolution ion channeling and TEM methods to investigate the damage production and dynamic annealing processes which take place in (100) silicon bombarded at elevated temperatures. Two important observations have arisen from our results i) We have observed an amorphisation process for Sb-implanted silicon at 250°C which is more akin to amorphisation processes in metals, whereby the impurity (Sb) appears to influence the stability of amorphous zones associated with individual ion tracks. ii) We have demonstrated that previously amorphised layers in silicon can be recrystallised through a solid phase epitaxial process by subsequent bombardment with He + , Ar + and Sb + ions at substrate temperatures of 300–400°C, which are significantly below normal thermal regrowth temperatures of >500°C.

Coherent-precipitate formation in Tl-implanted Si

Abstract Ion scattering, ion channeling, and cross-section electron microscopy were used to investigate Si single crystals implanted with 205Tl+ (0.29−1×1016 Tl/cm2, 90 keV) and annealed with pulses (1.6 J/cm2, 15 ns) from a ruby laser. Coherent precipitates of Tl were found to form as a result of laser processing. The systematics of the effect are presented and a formation mechanism proposed.