Boron diffusion in Si1-xGex alloy layers

The desire for higher carrier mobilities for thin-channel CMOS, such as fully-depleted SOI, has focused attention on the behavior of dopants in Si_1-xGe_x materials. In this work, the diffusion of boron implanted at 0.5 keV was studied for 5 sec anneals between 800 to 1050°C for silicon (Cz and epitaxial) and Si_1-xGe_x layers with Ge content of 7 and 25%. The implant dose of boron ions was 5 × 10¹⁴ ions/cm². The epi-silicon and Si_1-xGe_x layers were ∼200 nm thick so that the entire diffused profile was within the epitaxial layers. Strongly increased diffusion, compared to Cz- and epi-silicon, was found for boron atoms in layers with the Ge content of 7% and 25% for anneal temperatures above 900°C.