The dependence of stress in IBAD films on the ion-irradiation energy and flux

Systematic experimental studies of the stress build-up during e-gun deposition of Ni with simultaneous bombardment by energetic Ar+ ions (IBAD) have been carried out. The ion energy E was varied from 60 to 800 eV, and the ratio of the arrival rates of Ni atoms and Ar+ ions, R/J, was varied from 0.5 to 6.4. The Ni-deposition rate was in the range from 0.5 to 2.0 Angstrom/s, with all the depositions carried out near room temperature in a chamber with the base pressure of 5 x 10(-6) Pa. The film stress was measured by use of profilometry and the application of Stoney's equation. The experimental results were compared with predictions of a simple model proposed by Davis. This model assumes that the compressive stress build-up, due to knock-on implantation of film atoms being proportional to E-1/2, is balanced by relaxation by collision-cascade-excited atom migration proportional to E-5/3. TO Obtain agreement between model and experiment in the investigated ranges of E and R/J, an additional model parameter had to be added which takes into account that without irradiation, tensile stresses arise.