NI SILICIDES FORMATION AND PROPERTIES IN RF-SPUTTERED NI-100-X-SI-X THIN-FILMS

The temperature dependence of the electrical resistance R(T) for RF sputtered Ni-100-x-Si-x thin films (33 less than or equal to x less than or equal to 56 at%, as determined by Rutherford backscattering spectroscopy) was measured between -190 degrees C and the annealing temperature T, (T-a max = 300 degrees C). Structure investigations by X-ray diffraction revealed the preferential formation of silicide phases in as-deposited films as dependent on composition: gamma-Ni5Si2 (for x = 33), delta-Ni2Si (37 less than or equal to x less than or equal to 40) and zeta-NiSi2 (for x = 56). For intermediary compositions, amorphous alloys are formed. Annealing at 200 and 300 degrees C induces crystallization of the amorphous films into the gamma-Ni5Si2 phase (with zeta-NiSi2 admixture). The preferential formation of silicide phases is discussed taking into account the phenomenological rule of ''effective formation heat''. The temperature dependence of electrical resistance for as-deposited and annealed gamma and delta polycrystalline silicide thin films exhibits a classic metallic behaviour (different from that of polycrystalline Ni thin films). The very different R(T) behaviour of as-deposited and annealed polycrystalline zeta-phase is interpreted taking into account the weak localization contribution.