Sputtering yield amplification of Si through the addition of Cu, Mo, or Ta

Abstract In the sputtering process, the cascade of collisions in the target surface plays a crucial role, as it determines the emission mechanics of the sputtered atoms. This phenomenon is typically described for targets composed of a single elemental type. However, introducing a second element with a different atomic mass can alter the collision cascade. In 1992, S. Berg et al introduced a method to enhance the number of sputtered atoms from doped targets, a phenomenon known as Sputtering Yield Amplification (SYA). However, there seems to be a limit to the effective concentration of dopant atoms, and the reasons why certain dopants can promote or fail to produce SYA remain unclear. In this study, we investigated the influence of gas pressure on SYA of magnetron sputtering of a silicon target doped with molybdenum, tantalum, or copper, focusing on gas-phase collisions between the sputtered dopant atoms and the working gas atoms. Film thickness and total atomic deposition on the substrate were quantified using profilometry and Rutherford Backscattering Spectrometry. Optical Emission Spectroscopy (OES) was employed to monitor the emission intensities of neutral and ionized species in the plasma. Additionally, the SIMTRA code was used to model the spatial distribution of redeposited dopant atoms on the target surface. The results demonstrate that SYA was consistently observed across all tested pressures and dopant elements, indicating a significant increase in the sputtering yield under various experimental conditions.