Ion-plasma sputtering of Co and Mo nanometer thin films near the sputtering threshold

摘要

In this work, we present results of a study of low-energy (E-i < 200 eV) sputtering of Co and Mo nanometer thin films in high-density argon plasma of a low-pressure radio-frequency inductive discharge with a controlled incident ion energy and ion current density onto the sample. The average ion energy was determined by the negative self-bias potential, which arises when the RF bias power is applied to the substrate. The ion current density was determined from the ratio of the increments in the RF bias power and the self-bias potential. The sputtering rate was determined in situ by a refractometric method from a sharp change in the intensity of a reflected laser beam signal at the moment of a removal of a metal film. Precise control of sputtering made it possible to detect a formation of nanoscale structures at a stage near the end of sputtering of metal films. The experimentally determined sputtering yields of Co and Mo were in agreement with the results of semiempirical calculations. We demonstrate that for ion-plasma sputtering, removal of Co and Mo atoms occurs at ion energy lower than the sputtering threshold.