Metal‐dopant‐compound formation in TiSi2 and TaSi2: Impact on dopant diffusion and contact resistance

The refractory metal disilicides TiSi2 and TaSi2 were investigated for their usefulness as dopant diffusion sources. During furnace annealing and rapid thermal processing, strong decomposition reactions occur between the dopants D (B or As) and the respective silicide (MSi2) to form MxDy compounds. With the help of special sample preparation methods and various analytical techniques, the compound phases TiB2, TiAs, TaB2, and TaAs were unambiguously detected. The fraction of freely diffusing B in TaSi2 is determined to be below 5% of the total dose; by far, the major part of the dopant is bound within the TaB2 phase detected. Careful sample preparation and analysis of secondary‐ion‐mass spectrometry profiles is necessary to avoid artifacts caused by these compound particles. The MxDy‐compound formation has detrimental consequences: The solubility of arsenic and even more of boron in TiSi2 and TaSi2 is limited to rather low‐concentration levels (e.g., B in TaSi2: 4 × 1018 B/cm3 < CB(900 °C) < 1.6 × 1019 B/c...