Atomically controlled impurity doping for future Si-based devices

One of the main requirements for Si-based ultrasmall device is atomic-order control of process technology. Here we show the concept of atomically controlled processing based on atomic-order surface reaction control. Self-limiting formation of 1-3 monolayers of group IV or related atoms in the thermal adsorption and reaction of hydride gases (SiH₄, GeH₄, NH₃, PH₃, CH₄ and SiH₃CH₃) on Si(100) and Ge (100) are generalized based on the Langmuir-type model. Epitaxial Si or SiGe grown on N, P or B layers already-formed on Si(100) or SiGe(100) surface is achieved. It is found that higher level of electrical active P atoms exist in such film, compared with doping under thermal equilibrium conditions. Furthermore, the capability of atomically controlled processing for doping of advanced devices with critical requirements for dopant dose and location control is demonstrated for the base doping of SiGe:C heterojunction bipolar transistors (HBTs). These results open the way to atomically controlled technology for ultra-large-scale integrations.