Source Materials and Methods for Gallium Ion Implantation

Gallium (Ga) has been studied as an alternative p-type dopant to Boron (B) due to its higher solid solubility in Germanium (Ge) and silicon germanium (SiGe), which are used in advanced semiconductor devices for performance improvement. Recent developments in advanced PMOS devices reported that ultralow contact resistivity could be achieved by gallium doping [1, 2]. For ion implantation, gaseous dopant sources are generally preferred, however, for gallium implant the most common practical approach is to use a solid gallium compound target that is situated in the ion source plasma. An inert or fluoride containing gas is then flowed allowing physical sputtering and/or chemical reactions to occur with the solid gallium target. In this work, we examined Trimethylgallium (TMG or TMGa) - Ga(CH₃)₃ as a gas source material as well as multiple solid gallium compound targets in combination with different gases and gas mixtures. Gallium beam current performance and source conditions are reported to show potential performance benefits.