Effects of the dissolved oxygen in Ti films on Ti reactions in Cu/Ti/SiO₂/Si system upon annealing

Abstract

The reactions of Cu/Ti/SiO 2 structures at temperatures ranging from 200 to 700 • C have been studied for various Ti thicknesses. X-ray and Rutherford backscattering spectroscopy (RBS) analyses were used to identify the reaction products resulting from Ti reactions in Cu/Ti/SiO 2 systems and the oxygen composition in the unreacted Ti, and revealed a correlation between the oxygen concentration in Ti films and the sequences of the Ti reactions. The reaction products initially formed, at around 300 • C, were a series of Cu-Ti intermetallics (Cu 3 Ti/CuTi) at the Cu-Ti interface with the oxygen dissolved in the Ti moving from the compounds into the remaining unreacted Ti. At 500 • C, the Cu 3 Ti was converted into Cu-rich intermetallics, Cu 4 Ti, which grew at the expense of the CuTi due to the increased oxygen content in the Ti. In addition, the outdiffusion of Ti, to the Cu surface, and the Ti-SiO 2 reactions caused an abrupt increase in the oxygen content in the Ti layer, which placed thermodynamic restraints on further Ti reactions. Furthermore, thinner Ti layers showed a higher increased rate of oxygen accumulation for the same consumption of Ti, which led to significantly reduced Ti consumption. The diffusion barrier properties of SiO 2 for Cu metallization decreased with an increasing Ti thickness.

Effect of thin Mo2C layer on thermal stability of Si/SiO2/Ti/Cu system

“…The increased sheet resistance observed in the Ti-based Si/SiO 2 /Ti/Cu barrier structure measured after annealing at and above 400°C is ascribed to the formation of highresistance Cu-Ti intermetallics. It was also confirmed by XRD measurements and is in accordance with the literature (Hong et al 2004). The sharp decrease in the sheet resistance between 500 and 600°C may be due to titanium-free copper layer, which is a result of complete consumption of titanium in the formation of intermetallic compounds, and interface titanium oxide layer.…”

“…A single 60 nm thick titanium layer in the Si/SiO 2 / Ti/Cu system in the present investigation has been found to be thermally stable up to 400°C as reported in the literature (Hong et al 2004). Similar systems such as the Si/SiO 2 /Ta/Cu and the Si/SiO 2 /TaN/Cu when tested under the MOS device structure were found to fail at 600°C temperature (Loh et al 2004).…”

“…The sharp decrease in the sheet resistance between 500 and 600°C may be due to titanium-free copper layer, which is a result of complete consumption of titanium in the formation of intermetallic compounds, and interface titanium oxide layer. The effect of increased titanium thickness in the Si/SiO 2 /Ti/Cu structure has been reported to decrease the thermal stability (Hong et al 2004). Therefore, instead of using a thicker titanium barrier layer in the structure, a bi-layered barrier may prohibit titanium copper intermetallics formation and may result in increased thermal stability of the system.…”

Effect of Annealing Ambient on the Self-Formation Mechanism of Diffusion Barrier Layers Used in Cu(Ti) Interconnects

“…8b), the Ti atoms reacted with both impurity oxygen (where the O 2 partial pressure of 0.2 Pa was thermodynamically enough to oxidize titanium) and the SiO 2 substrate, because the DG f s values of Ti compound formation of oxides and silicides were very low (i.e., )882.9 kJ mol )1 for TiO 2 and )581.4 kJ mol )1 for Ti 5 Si 3 ). 20 Both the self-formation of the Ti-rich barrier and passivated TiO x surface layers occurred due to diffusion and surface/interfacial reaction of the Ti atoms. In the case of sample B 1 annealed in UHV (Fig.…”

Multifractal analysis for Cu/Ti bilayer thin films

“…Ti is easy to react with SiO 2 to produce thin barrier metal layers by self‐formation in SiO 2 ‐based low‐k interlayers . Cu/Ti films and alloys have been widely studied because of the excellent electrical and metallurgical properties . The performance of nanostructured devices with morphological features at nano‐scale strongly related to the surface roughness.…”