Helium implantation induced metal gettering in silicon at half of the projected ion range

He⁺ ions were implanted at 40 keV into Si <100> random direction at room temperature to fluences between 5×10¹⁵ He⁺/cm² and 3.5×10¹⁶ He⁺/cm². The samples were than contaminated with Cu in order to study the gettering of Cu atoms at the defective layer. A subsequent annealing at 800ºC was performed in order to recover the implantation damage and redistribute the Cu into the wafer. The samples were analyzed by Rutherford backscattering/channeling (RBS/C) and transmission electron microscopy (TEM) techniques. The Cu distribution was measured by secondary ion mass spectrometry (SIMS). The SIMS results show that the 5×10¹⁵ He⁺/cm² implant induces gettering at the He⁺ projected range (Rp) region, while the 8×10¹⁵ He⁺/cm² and 3.5×10¹⁶ He⁺/cm² implants have resulted in gettering at both the Rp and Rp/2 depths. The TEM micrographs show no visible defects at Rp/2 region. This corresponds to the so called Rp/2 gettering effect. It is important to note that in this study the Rp/2 related effect is observed after an implantation of a light ion at low energy.