Direct evidence of arsenic clustering in high dose arsenic-implanted silicon

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Abstract
High dose (5–7.5×1015 cm−2) arsenic implantation was conducted in the energy range 50–120 keV into three types of (100)Si substrates: (i) bare Si, (ii) with a thermally grown screen oxide (775 Å), and (iii) preamorphized surface layer produced by self-implantation. The substrates were subsequently furnace annealed at 600 °C in N2. Cross-section transmission electron microscopy (XTEM) revealed that in all cases discrete layers of As related clusters and small dislocation loops occurred at depths matching the projected ranges of As into the Si substrates and original amorphous/crystalline interfaces respectively. The atomic profiles of As obtained by secondary ion mass spectrometry (SIMS) from these samples did not show any redistribution of As. The carrier concentration profiles from the spreading resistance measurements indicate that only 30% of As was electrically active. Comparison of XTEM and SIMS suggests that nucleation of the clusters occurred in the regions where As was present above the solid solubility limit in Si. The presence of recoiled oxygen has been found to stabilize the clusters.