Performance comparison of enriched versus non-enriched SDS GeF4

The use of germanium as a preamorphization implant to control channeling in a subsequent boron implant, and in reducing the resistance of titanium silicide has been published. However, since the most abundant naturally occurring isotope of germanium is ⁷⁴Ge, counter doping from arsenic residuals in the implanter is a concern. The implanter´s capability to resolve unwanted species and produce high current beams of the desired isotope is also challenged with natural abundance germanium. Isotopically enriched SDS ⁷²GeF₄ is proposed as a solution for these problems. Spectra of both natural abundance and mass 72 enriched GeF₄ SDS were compared and the abundance of each isotope measured. Beam current performance of the two gases is also compared. SIMS analysis is used to quantify both the implanter´s ability to resolve enriched ⁷²Ge and the efficiency of various cleaning techniques to remove arsenic residuals from the ion source and beamline