Magnetron sputter deposition of A-15 and BCC crystal structure tungsten thin films

The effect of processing parameters on the crystal structure and electrical resistivity of magnetron sputter deposited W thin films was investigated. Formation of body centered cubic (bcc) W was favored when the concentration of impurity oxygen atoms in the films was < 5 at.% while the formation of A-15 W was favored between 6-10 at.% O. A transition from A-15 W films to bcc W films occurred as the O was removed from the deposition chamber by presputtering the target for extended periods of time. The binding energies of the W atoms in A-15 and bcc W films are similar, as is the binding energy of the O atoms in the two different crystal structures, indicating that the O is not present as a tungsten oxide compound. The resistivity of A-15 W films is always higher than the resistivity of bcc W films due to the increased O concentration and small grain size of the A-15 films. However, the sputter deposition pressure is found to have a greater effect on resistivity. This is attributed to the formation of cracks in the film.