Effect of electron cyclotron resonance H/sup +/, Ne/sup +/, Ar/sup +/, and Xe/sup +/ plasma precleaning on titanium silicide formation

A vacuum integrated cluster tool process incorporating electron cyclotron resonance plasma cleaning, Ti sputter deposition, and rapid thermal annealing in N/sub 2/ is used to form a TiN/sub x<1//TiSi/sub y/ bilayer on (100) Si where the film composition is controlled by the preclean chemistry. Chemical cleaning with nominal 10 eV H/sup +/ completely removes native Si oxide resulting in a hydrogen terminated surface that promotes silicidation compared to one cleaned with buffered-oxide-etching (BOE). If the native oxide is only partially reduced, viz., SiO/sub x<2/ surface, for example by shortening the H/sup +/ exposure time, then silicidation is largely inhibited and a thicker nitride layer is formed. Sputter cleaning with 50 to 250 eV Ar/sup +/ results in a bilayer that is roughly equivalent to that formed with BOE, whereas 50 to 150 eV Xe/sup +/ bombardment favors nitridation. Precleaning with >150 eV Ne/sup +/ promotes silicidation, thereby minimizing nitride thickness. The effects of precleaning are significant as the activation energy for TiSi/sub y/ formation is reduced from 1.8 eV characteristic of a BOE cleaned surface to 1.2 eV on Si etched with 250 eV Ne/sup +/. Mechanistically, the silicide kinetics are shown to be inhibited by the presence of a thin amorphous layer that is formed only when cleaning Si with Ar/sup +/ and Xe/sup +/ with the effect that both knock-on oxygen atoms and implanted noble gas atoms trapped within the amorphous layer retard the requisite solid-phase epitaxial regrowth kinetics. Recrystallizing the amorphous Si surface prior to metallization appears to restore the near-normal silicide kinetics that is characteristic of Ne/sup +/ cleaning.<
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