Impact of some process variations on NiFe thin films

Rutherford backscattering spectrometry (RBS) and Auger electron spectroscopy (AES) are used to detect changes in stoichiometry and impurity incorporation in thin, rf diode sputtered NiFe films as a function of processing variations. Comparisons are made to thin, evaporated NiFe films with respect to oxygen reactivity. Because Ni and Fe are close in atomic weight, RBS, using 2‐MeV He incident ions, cannot resolve them. However, by increasing the He incident energy to 4.7 MeV, the (26)Fe(56) and (28)Ni(58) isotopes are resolvable in films thinner than about 250 Å and the actual NiFe thin‐film stoichiometry can be calculated. Complementary AES depth profiling measurements indicate Fe enrichment by approximately 5 wt. % as the deposition substrate bias is increased from 0 to −200 V. Magnetic characterization shows a corresponding increase in easy‐axis coercivity of more than a factor of 10. Other magnetic parameters are also adversely affected.