Activation analytical investigation of contamination and cross-contamination in ion implantation

Abstract

In silicon layers, implanted at 100–150 keV with P⁺, As⁺ and Ar⁺ ions, considerable Fe, Cr, Ni, Co and Cu were detected by means of neutron activation analysis. With the elements of the Fe group, concentrations up to 5.10¹⁴cm⁻² were obtained, whereby the relationship of these elements to each other corresponds to the composition of the stainless steel apertures used. The contamination of the layers is dose dependent. In accordance with the sputter rates, As⁺ ion implanted layers are more contaminated than those implanted by P⁺ or Ar⁺ ions. Additionally, the implanting process introduces, besides the contamination with heavy metals, dopants from the previous implantation. This so-called cross-contamination amounted to approx. 0.3 % of the implanted ion dose.