Fabrication of C54-titanium silicide thin films using pulsed cathodic arc deposition and rapid thermal annealing

Due to its low electrical resistivity and high thermal stability, C54-TiSi2 thin films have been widely used as contact and interconnect material in microelectronic devices. Compared to highly-doped polysilicon thin films, C54-TiSi2 has much lower electrical resistivity and similar mechanical properties. Thus, it is a promising material to be used as a highly conductive or structural material in surface micromachining technologies. In this dissertation, TiSi2 thin films have been prepared for the first time by using cathodic arc deposition to study the impact of energetic ion bombardment on film microstructure and subsequent C49-C54 phase transformation during rapid thermal annealing.; The first part of this dissertation investigated the relationship between the arc film deposition conditions and the resultant TiSix thin film composition, microstructure and resistivity. Using TiSi2 compound as the cathode material, TiSix thin films were deposited at varied substrate bias (floating ∼ -200V), substrate temperature (room temperature ∼ 450°C) and the Ar gas pressure (3∼20mTorr). It was found that the film deposition rate and the Si content in the films decreased substantially with increasing the substrate bias. At the Ar pressure of ∼3mTorr and under no substrate heating, the TiSix film composition varied from x=2.4 to x=1.4 when the substrate bias was changed from floating to -200V. In comparison, the Ar pressure was shown to have a small effect on the film deposition rate and film composition at a floating substrate bias. The as-deposited TiSix films had an amorphous structure at low substrate temperatures (≤350°C). After applying a negative substrate bias, a phase separation was observed in the amorphous phase. The Si atoms were seen to segregate around Ti rich domains at nano scales in the amorphous films and the domain size increased with the magnitude of the substrate bias. At the substrate temperature of 450°C, the as-deposited TiSix thin films had quite different microstructure depending on the substrate bias. The film had a well-crystallized C49 structure with small grain size (∼30nm) when deposited at the substrate bias of -100V At a floating substrate bias, the film was a mixture of nanocrystalline Si and amorphous phase. At the substrate bias of -175V the film was mainly amorphous with partially crystallized C49 phase.; In the second part of the dissertation, the C49-C54 phase transformation was studied in the arc-deposited TiSi2 thin films during rapid thermal annealing. It was found that the C49-C54 phase transformation was retarded to a higher annealing temperature (>900°C) in the arc-deposited TiSi2 films compared to evaporated or sputter deposited films. For a 90mm-thick TiSi2 film deposited by the cathodic are deposition on a SiO2/Si substrate, the activation energy of the C49-C54 transformation was calculated to be 6.1+/-0.2eV. The C54-TiSi2 phase formation and film stress was studied and compared for 100nm-thick TiSix films deposited on bare Si (111) substrates at different deposition conditions. The films exhibited similar behaviors on the C49-C54 phase transition during rapid thermal annealing. After the annealing at 950°C for 60s, the resultant C54-TiSi2 films displayed a reduced residual film stress (∼1 GPa) compared to evaporated or sputtered films.