Tungsten films were deposited on Si substrates by the H2 or Si reduction of WF6 under various experimental conditions. The composition and structure of as-deposited samples as well as the interfacial reactions and interdiffusion of elements in annealed samples were characterized by nuclear reaction analyses, sheet resistance measurements, x-ray diffraction technique, and Rutherford backscattering spectroscopy. The amount of oxygen at W–Si interfaces was found to be dependent on the cleaning treatment of the Si surface used before WF6–Si interaction. The interfacial oxygen concentration was less than 1 ⊠ 1014 at./cm2 (detection limit of the nuclear reaction analysis) and (2–7) ⊠ 1016 at./cm2 using an HF cleaning and the RCA treatment, respectively. For W/Si samples, the formation temperature of WSi2 was dependent on the dopant level in the Si substrates and the oxygen concentration at W–Si interfaces. The silicidation reaction occurred at 625 °C in “oxygen free” W/Si structures while for structures containing interfacial oxygen atoms, this reaction occurred above 800 °C. In Al/W/Si structures, the intermetallic compound, WAl12, was formed by annealing at 450 °C for 90 min. Furthermore, the formation of WSi2 was observed in structures annealed at a temperature in the range of 550 °C–600 °C regardless of the oxygen concentration at the W–Si interface. A model to explain the effect of interfacial oxygen atoms on the silicidation reaction and the influence of the Al overlayer on the thermal stability of Al/W/Si structures is proposed and discussed in this paper.
We describe the fabrication and characterization of high speed SiGe:C HBTs using a poly-SiGe emitter. The effects of Ge incorporation into the emitter on the static (gain, BVCEO) and dynamic (fT, T~~) device characteristics are analyzed. This experiment is used to quantify the impact of the current gain on fT, and provides an original way to extract the emitter component of the forward transit time.
This paper reports the investigation of MOCVD (Metal Organic Chemical Vapor Deposition) TiN, and IMP (Ionized Metal Plasma) Ta and TaN thin films as barrier layers for copper metallization. Evaluation of both deposition techniques including step coverage, Cu adhesion, Cu diffusion and selectivity regarding Cu-CMP process have been performed. Successful implementation with copper metallization in high aspect ratio line and via patterns is reported.
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