G. Carter

Annealing of isolated amorphous zones in silicon

In situ transmission electron microscopy has been used to observe the production and annealing of individual amorphous zones in silicon resulting from impacts of 200-keV Xe ions at room temperature. As has been observed previously, the total amorphous volume fraction decreases over a temperature range from room temperature to approximately 500 °C. When individual amorphous zones were monitored, however, there appeared to be no correlation of the annealing temperature with initial size: zones with similar starting sizes disappeared (crystallized) at temperatures anywhere from 70 °C to more than 400 °C. Frame-by-frame analysis of video recordings revealed that the recovery of individual zones is a two-step process that occurred in a stepwise manner with changes taking place over seconds, separated by longer periods of stability.

The effects of radiation damage and impurities on void dynamics in silicon.

Abstract Transmission electron microscopy (TEM) has been used to study the effects of implanted oxygen or carbon on the dynamics of cavity growth in silicon. The cavities are produced by implantation with helium ions followed by annealing to convert small He-filled bubbles into large empty voids. We have also investigated the effects of self-ion damage on cavity growth. Both impurities and self-ion damage can significantly inhibit void growth. In addition, hot stage TEM has been used to elucidate the processes responsible for cavity growth in an attempt to understand the way in which both impurities and radiation damage are able to modify these processes. Cavity growth is seen to be due to Ostwald ripening and coalescence in the early stages with some sporadic, rapid motion of large bubbles leading to coalescence at higher temperatures. Our research indicates that void dynamics in silicon are quite different from those in metallic systems.

The influence of impurities on the growth of helium-induced cavities in silicon

The effects of implanted oxygen, carbon, nitrogen, and self-damage on the growth of helium-induced cavities in silicon during high-temperature annealing have been studied. Impurities and helium were implanted into silicon at room temperature. Annealing at temperatures above 1000 K converts small He-filled bubbles into larger empty voids. The mean void size after annealing for 30 min at 1173 K was significantly reduced by the presence of all three implanted impurities. In extreme cases, the mean void radius is reduced from 10 nm, for a pure He implant, to 2.8 nm in a C pre-implanted sample. On the other hand, self-ion damage, unless at or near the level sufficient to cause amorphization, does not significantly affect cavity growth during annealing. We speculate that the presence of impurities significantly reduces the movement of voids by pinning them to dislocations or impurity aggregates or by chemical reactions at the void surfaces.

Shallow BF2 implants in Xe-bombardment-preamorphized Si: The interaction between Xe and F

Si(100) samples, preamorphized to a depth of ∼30nm using 20 keV Xe ions to a nominal fluence of 2×1014cm−2 were implanted with 1 and 3 keV BF2 ions to fluences of 7×1014cm−2. Following annealing over a range of temperatures (from 600 to 1130 °C) and times the implant redistribution was investigated using medium-energy ion scattering (MEIS), secondary ion mass spectrometry (SIMS), and energy filtered transmission electron microscopy (EFTEM). MEIS studies showed that for all annealing conditions leading to solid phase epitaxial regrowth, approximately half of the Xe had accumulated at depths of 7 nm for the 1 keV and at 13 nm for the 3 keV BF2 implant. These depths correspond to the end of range of the B and F within the amorphous Si. SIMS showed that in the preamorphized samples, approximately 10% of the F migrates into the bulk and is trapped at the same depths in a ∼1:1 ratio to Xe. These observations indicate an interaction between the Xe and F implants and a damage structure that becomes a trapping sit...

Damage profiles of ultrashallow B implants in Si and the Kinchin-Pease relationship

Damage distributions resulting from 0.1–2keV B+ implantation at room temperature into Si(100) to doses ranging from 1×1014 to 2×1016cm−2 have been determined using high-depth-resolution medium-energy-ion scattering in the double alignment mode. For all B+ doses and energies investigated a 3–4nm deep, near-surface damage peak was observed while for energies at and above 1keV, a second damage peak developed beyond the mean projected B+ ion range of 5.3nm. This dual damage peak structure is due to dynamic annealing processes. For the near-surface peak it is observed that, at the lowest implant energies and doses used, for which recombination processes are suppressed due to the proximity of the surface capturing interstitials, the value of the damage production yield for low-mass B+ ions is equal or greater than the modified Kinchin-Pease model predictions [G. H. Kinchin and R. S. Pease, Rep. Prog. Phys. 18, 1 (1955); G. H. Kinchin and R. S. Pease, J. Nucl. Energy 1, 200 (1955); P. Sigmund, Appl. Phys. Lett. ...

Theory of ripple topography inhibition in depth profiling with sample rocking

A theory is developed which explains how sample rocking during ion beam sputtering erosion can inhibit ripple formation, observed with monodirectional ion incidence, on radiation amorphisable materials. The model assumes curvature dependent sputtering yield and random ion arrival and sputtering as roughening processes and radiation mediated viscous flow and ballistically driven effective surface diffusion as smoothing processes.

Medium energy ion scattering analysis of the evolution and annealing of damage and associated dopant redistribution of ultra shallow implants in Si

As junction depths in advanced semiconductor devices move to below 20 nm, the process of disorder evolution during ion implantation at ultra low energies becomes increasingly influenced by the surface. This may also hold for shallow regrowth and dopant redistribution processes during subsequent thermal annealing of the substrate. The investigation of these near-surface processes requires analytical techniques with a depth resolution of≤1 nm. Medium energy ion scattering (MEIS) has the unique capability of simultaneously providing quantitative, high-resolution depth distributions of implant disorder (displaced Si lattice atoms) and of implanted atoms, albeit not of light species. We report here a comparative MEIS investigation into the growth mode of shallow disordered/amorphised layers during≤1 keV B+ and 2.5 keV As+ ion implantation into Si. In both cases the growth of the damage depth profiles differs significantly from the energy deposition function, as it is strongly determined on the one hand by the proximity of the surface acting as a nucleation site for migrating point defects formed during implantation, which results in planar growth of the amorphous layer, and on the other by the dynamic annealing processes operating at room temperature. When such defect recombination processes are inhibited, e.g. for low dose, ultra shallow 200 eV B+ implants, MEIS shows that defect production yields exceeding the Kinchin–Pease model predictions are achieved. For As implants, a correlation is observed between the movement of the As and the depth of the growing, planar amorphous layer. Thermal annealing of As implanted samples at different temperatures and durations leads to solid phase epitaxial regrowth. During regrowth, MEIS shows that there is a close correlation between damage dissolution, the movement of nearly half of the As dopant into substitutional sites and the snowploughing of a fraction of the As in front of the advancing amorphous/crystalline interface leading to the formation of a less than 1 nm wide As pile-up layer trapped under the oxide.

The use of cavities for gettering in silicon microelectronic devices

This paper presents results from an ongoing three-year project in which the use of microcavities to getter transition metal impurities in silicon-based microelectronic devices has been investigated. The paper reports on the results of a fundamental study of bubble growth mechanisms and on a systematic study of possible detrimental effects of cavity gettering on 1.2 μm p-type metal–oxide-semiconductor field effect transistors.

Defect production and stability in high-energy-density cascades in Ni

Abstract Ion implantation into Ni single crystals was carried out at 40 K and room temperature using monatomic Sb + and diatomic Sb 2 2 ions for implantation doses in the range ∼ 2 × 10 13 −2 × 10 14 Sb + cm −2 . The damage level after each implant was measured in situ by observing the Rutherford backscattering yield of 2.0 MeV 4 He + ions channeled along the 〈110〉 axis. More damage is retained for low temperature Sb + and Sb 2 + implants and room temperature Sb 2 + than for Sb + implants at room temperature. In the ion fluence regime studied the damage retained, N D , is a non-linear function of ion fluence Φ.