A transmission electron microscopy (TEM) study on the proximity gettering with high energy carbon ion ($C^+$) implantation has been carried out.
The substrates were CZ (001) silicon wafers. Implantation energy of $C^+$ was 3 MeV and doses ranged from $1 × 10^{15}$ to $1 × 10^{16}/㎠$. P ions were implanted under conditions of 3 MeV and a $1 × 10^{15}/㎠$ dose for all samples. Implanted samples were then annealed in a vaccum ambient at 550 ~ 1000℃ for 30 ~ 60 min. Residual defects were studied using cross-sectional TEM and lattice strain were measured by double crystal X-ray diffraction (DCXRD).
X-ray rocking curve analyses indicate that the lattice strain concentrated around $R_p$ of $C^+$ implanted sample is the same as in the both $P^+$ and $C^+$ implanted sample. The lattice strain remained near surface in the only $P^+$ implanted sample is eleminated by additional $C^+$ implantation. These results mean no mass flux from the $P^+$ implanted layer to the $C^+$ implanted layer during annealing.
The TEM results show that the upper band of the damaged region formed by $P^+$ implantation is removed while the bottom of that is not removed in the double ion implanted samples. The <112> elongated rodlike defect is proved to be vacancy-type defect under the high-resolution TEM study. Even though $R_p$ of $P^+$ is 800 nm away from that of $C^+$, the secondary defect induced by $P^+$ implantation could be reduced by additional $C^+$ implantation and these effects become obvious with the increases of annealing temperature, annealing time and dose.
The observed defect behavior by TEM was interpreted by Monte Carlo computer simulations using TRIM-code. The interstitial rich region due to $P^+$ implantation and the vacancy rich region due to $C^+$ implantation may almost overlap.
From the above results, the following conclusion is deduced. The silicon self interstitials, sources of the secondary defect, combine with vacancies formed along C ion's track and annihilate. This can be the main atomic mechanism of the gettering phenomena with high energy $C^+$ implantation.
