WN Films Research Articles

Effects of Nitrogen Ion Energy on the Growth Mode of WN Films Deposited by Reactive Ion Beam Sputtering

ABSTRACTWN films were deposited on clean Si substrates by Reactive Ion Beam Sputtering in a UHV system. The growth mode of the films as a function of the nitrogen ion energy was investigated by in situ Auger Electron Spectrometry. The energy of the incident ions was varied from 250 eV to 3 keV. We observed a significant nitridation of the silicon at the very beginning of the deposition. This nitridation is more pronounced for the lower energy and is more reduced for 2 keV-ions. It seems to follow the trend of the film composition: 250 eV-ions and 2 keV-ions result in N-rich films (N/W≈1) and W-rich films (N/W≈0.5), respectively. All these results are discussed in terms of sputtering yield, backscattering and sticking coefficient and are explained by taking into account: first, the interaction between the incident ions and the target, and second, the interaction between the species emitted by the target and the growing film.

Effects of impurities on the interface of ion beam sputtered tungsten with silicon

In this study, we have investigated the properties of the interface of ion-beam-sputter-deposited-W (IBSD-W) with silicon modified by the presence of an interfacial contamination (oxygen, nitrogen or boron). Auger electron spectroscopy combined with depth profiling was used to investigate the growth mode of IBSD-W onto Si as well as the redistribution of elements during in-situ thermal annealing. The growth mode is strongly affected by the incident ion energy and the presence of an interfacial oxide. We found that a thin oxide layer (≈ 2 ML) is not an efficient barrier to prevent silicon diffusion toward the metal surface. A thicker oxide (≈ 6 ML) greatly limits the silicon diffusion and inhibits silicide formation up to 700°C. Finally, the deposition of WN films by reactive ion beam sputtering leads to the nitridation of the silicon substrate and a stable contact up to 700°C.

Studies in contact potentials : I. Determination of the surface potential of some films on tungsten and mercury by the condenser method and a new form of the thermionic method

AbstractThe author first decribes a new form of the thermionic method based on the shift of resistance characteristics. The resistance of the diode is measured with an A.C. bridge, care being taken to keep the emitter at constant temperature, even in the presence of gas. Cells suitable for tungsten deposits are described. The WH, WXe, and HgXe films have been studied by both the thermionic and the condenser method, and excellent agreement has been found for the surface potentials. For the WH and WN films, the surface potentials obtained are in grave disagreement with those of Bosworth 4) and of Bosworth and Rideal 5, 6) on tungsten wires. It is shown that Bosworth's value cannot refer to a WH film. The work function of a deposit stabilized between 293 and 428° K is close to that of a polycrystalline wire. Sintering increases the work function.