Suppression of boron diffusion by fluorine implantation in preamorphized silicon

We have investigated the role of fluorine in the reduction of transient enhanced diffusion (TED) and thermal diffusion (TD) of B in preamorphized Si layers implanted with F. For this purpose, we have employed B delta-doped layers, grown by molecular beam epitaxy (MBE), as markers for silicon self-interstitials (Is). We have shown that boron TED decreases with increasing amount of incorporated F up to the complete TED suppression. Furthermore, we have clearly demonstrated that the physical mechanism that suppresses the boron TED is not a B-F chemical bonding, but a strong interaction between F atoms and Is. In addition, we have seen that fluorine strongly reduces B diffusion also under Is thermal equilibrium concentration. Our results clearly show that the presence of F lowers the Is density very effectively, reducing the boron TED as well as the dopant diffusion under equilibrium conditions.