Sputtered W–N diffusion barriers

The thermal stability of reactively sputtered tungsten–nitrogen alloy thin films is investigated for the application as diffusion barriers in silicon contact metallizations. The composition of W–N barriers is varied over a wide range including pure W. Aluminum, gold, and silver are used as low resistivity overlayers. Metallurgical interactions at temperatures ranging from 500 to 900 °C are studied. Incorporating nitrogen into tungsten advantageously stabilizes all three systems. The overall failure takes place rapidly above critical temperatures that depend on both the metal overlayer and the microstructure of the barrier. In some cases, W–N alloys can effectively prevent interdiffusion at temperatures as high as 800 °C for 30 min

Thermal stability and nitrogen redistribution in the〈Si〉/Ti/W–N/Al metallization scheme

Backscattering spectrometry, Auger electron spectroscopy, and x‐ray diffraction have been used to monitor the thin‐film reactions and nitrogen redistribution in the 〈Si〉/Ti/W–N/Al metallization system. It is found that nitrogen in the W–N layer redistributes into Ti after annealing at temperatures above 500 °C. As a consequence of this redistribution of nitrogen, a significant amount of interdiffusion between Al and the underlayers is observed after annealing at 550 °C. This result contrasts markedly with that for the 〈Si〉/W–N/Al system, where no interdiffusion can be detected after the same thermal treatment. We attribute this redistribution of nitrogen to the stronger affinity of Ti for nitrogen than W. If the Ti layer is replaced by a sputtered TiSi_(2.3) film, no redistribution of nitrogen or reactions can be detected after annealing at 550 °C for 30 min

Bias‐induced stress transitions in sputtered TiN films

We report on intrinsic stress properties of magnetron sputtered titanium nitride films deposited under different conditions. By proper selection of processing parameters, films with low stress can be obtained. Unstressed film formation is favored by low substrate bias voltage, high pressure, or use of heavy sputtering gases. Stress relief is, however, accompanied by an increase in resistivity and a decrease in film density. As a result of these changes the effectiveness of such titanium nitride films as diffusion barriers between silicon and aluminum is minimal

Bias-induced stress transitions in sputtered TiN films

We report on intrinsic stress properties of magnetron sputtered titanium nitride films deposited under different conditions. By proper selection of processing parameters, films with low stress can be obtained. Unstressed film formation is favored by low substrate bias voltage, high pressure, or use of heavy sputtering gases. Stress relief is, however, accompanied by an increase in resistivity and a decrease in film density. As a result of these changes the effectiveness of such titanium nitride films as diffusion barriers between silicon and aluminum is minimal

Microstructure and mechanical properties of nitrided molybdenum silicide coatings

Mo-Si-N films with a high nitrogen concentration were produced by sputter-deposition in nitrogen plasma. Chemical composition was determined with Rutherford backscattering and nuclear reaction analysis. Ratio of Mo to Si was 1:2 in the coatings with a nitrogen concentration of 50%. Microstructure of the as-deposited coatings on a silicon substrate was amorphous and no crystallization was found after annealing up to 1000{degree}C, although some relaxation was observed in X-ray diffraction. This was confirmed by high-resolution TEM. Hardness of Mo-Si-N films was 18.8 GPa as determined with a nanoindenter. This is significantly higher than that of MoSi{sub 2} films, 11.2 GPa. Hardness of the Mo-Si-N films increased to 24.4 GPa after annealing at 800{degree}C, which is the same as that of the tetragonal phase of MoSi{sub 2}, 25.5 GPa. Similarly, modulus of as-deposited Mo-Si-N film was higher (257 GPa) than that of MoSi{sub 2} film (222 GPa). However, only a slight increase in the modulus of the Mo-Si-N film was found after annealing at 800C, whereas the modulus of the crystallized tetragonal MoSi{sub 2} was 382 GPa. No cracking was found in the Mo-Si-N films even after annealing at 1000C