Kinetics of arsenic activation and clustering in high dose implanted silicon.

We have observed a meta-stable state in the activation of high dose arsenic implanted silicon. This state is marked by a local minimum in the sheet resistance which increases to a local maximum as the anneal time increases. Sheet resistance data in conjunction with Rutherford backscattering and channeling, and transmission electron microscopy indicate that the initial minimum in sheet resistance is due to activation of arsenic atoms by occupying substitutional sites as the amorphized silicon layer recrystallizes. The subsequent clustering of arsenic atoms is the cause for the increase in the sheet resistance, while the final decrease is associated with the lateral diffusion of arsenic into the bulk silicon. We have studied this effect in the 850C to 1200C temperature range, and have obtained an activation energy of 1.0 eV for the clustering of arsenic atoms.