Doping by Secondary Implantation

Abstract

The dopants usually employed in Si molecular beam epitaxy have been found to exhibit adlayer formation as well as a low coefficient of spontaneous incorporation. The dopant incorporation based on the interaction of Si+ ions with dopant adatoms is proposed as a doping method denoted as doping by secondary implantation. Experimental results on secondary implantation of Sb into (100) Si MBE layers are presented. Si ions are employed that either originate from the electron‐gun‐heated silicon source itself or optionally from a cross beam ionization ring on top of the silicon source. Doping uniformity within a 3 in. wafer is found to be in the 5% range. Dopant activation coefficients of almost unity at least up to a doping level of 1019 cm−3 are found, without mobility degradation and without evidence of a simultaneous dopant adlayer sputtering at a growth temperature of 650°C and ion energies up to 1000 eV. Results from secondary implantation experiments are expected to be a suitable tool for the analysis of adlayer properties such as e.g., cluster formation.