Magnetic-field-enhanced rf argon plasma for ionized sputtering of copper

A multipole magnetic field was used to increase the ion density of an inductively coupled rf (13.5 MHZ) argon plasma for ionized magnetron sputtering of copper (Cu). Langmuir probe measurements showed an increase of plasma density over a factor of 2 with the application of the magnetic field. At an argon pressure of 15 mTorr and a rf power of 600 W, an ion density of 1.2×1012 ions/cm3 was achieved. When this plasma was applied to ionize the magnetron sputtered Cu vapor, a high emission intensity ratio from the Cu+ ion line to the Cu neutral line was observed from the optical emission spectroscopy, suggesting a high ionization fraction for the sputtered Cu vapor.