Thermal reaction of Pt film with 110 GaN epilayer

Backscattering spectrometry, x-ray diffractometry, and scanning electron microscopy have been used to study the reaction of a thin Pt film with an epilayer of [110] GaN on [110] sapphire upon annealing at 450, 550, 650, 750, and 800 degrees C for 30 min. A Ga concentration of 2 at. % is detected by MeV He-4(++) backscattering spectrometry in the Pt layer at 550 degrees C. By x-ray diffraction, structural changes are observed already at 450 degrees C. At 650 OC, textured Ga2Pt appears as reaction product. The surface morphology exhibits instabilities by the formation of blisters at 650 degrees C and voids at 800 degrees C

Reactively sputtered RuO2 diffusion barriers

The thermal stability of reactively sputtered RuO2 films is investigated from the point of view of their application as diffusion barriers in silicon contact metallizations with an Al overlayer. Backscattering spectra of Si/RuO2/Al samples and electrical measurements on shallow junction diodes with Si/TiSi2.3/RuO2/Al contacts both show that RuO2 films are effective diffusion barriers between Al and Si for 30-min annealing at temperatures as high as 600°C

Instability of Amorphous Ru-Si-O Thin Films under Thermal Oxidation

Ternary films about 200 nm thick of composition Ru20Si15O65 have been synthesized by reactive rf magnetron sputtering of a Ru1Si1 target in an argon-oxygen gas. As-deposited, the films are X-ray-amorphous. Their atomic density is 8.9 × 10^22/cm^3 (5.1 g/cm^3), and their electrical resistivity is in the range of 2 mOmega cm. After annealing in dry oxygen at 600°C for 30 min, micron-sized grains of RuO2 grow out of the film and volatile RuO4 escapes. The significance of these results is discussed

Films of Ni–7 at% V, Pd, Pt and Ta–Si–N as diffusion barriers for copper on Bi2Te3

Films of Ni–7 at% V, Pt, Pd, and Ta40Si14N46, each approximately 100 nm thick, were magnetron-deposited and interposed between about 250 nm thick copper overlayers and Bi2Te3 single-crystalline substrates. The samples were then annealed in vacuum up to 350 degrees C. The performance of the metal and the tantalum-silicon-nitride films as diffusion barriers for in-diffusion of Cu and out-diffusion of Bi and Te was evaluated by 2.0 MeV 4He backscattering spectrometry and x-ray diffraction. The Ni–7 at% V, Pd and Pt films all fail to prevent interdiffusion of Cu and Bi2Te3 after a few hours of annealing at 200 degrees C. However, the Ta40Si14N46 barrier preserves the integrity of the contact after 250 degrees C for 50 h and 350 degrees C for 1 h anneals. These results confirm the superior characteristics of the metal-silicon-nitride films as diffusion barriers

WxN1–x alloys as diffusion barriers between Al and Si

Reactively sputtered tungsten nitride (WxN1–x) layers are investigated as diffusion barriers between Al overlayers and Si shallow n + -p junctions. Both amorphous W80 N20 and polycrystalline W60 N40 films were found to be very effective in preserving the integrity of the n + -p diodes for 30-min vacuum annealing up to 575 °C. Diode failure at higher temperatures is caused by localized penetration of Al into through the WxN1–x barriers. The effectiveness of the barrier decreases for polycrystalline W90 N10 and is worse for pure W

Tantalum-based diffusion barriers in Si/Cu VLSI metallizations

We have studied sputter-deposited Ta, Ta36Si14, and Ta36Si14N50 thin films as diffusion barriers between Cu overlayers and Si substrates. Electrical measurements on Si n + p shallow junction diodes demonstrate that a 180-nm-thick Ta film is not an effective diffusion barrier. For the standard test of 30-min annealing in vacuum applied in the present study, the Ta barrier fails after annealing at 500 °C. An amorphous Ta74Si26 thin film improves the performance by raising the failure temperature of a /Ta74Si26(100 nm)/Cu(500 nm) metallization to 650 °C. Unparalled results are obtained with an amorphous ternary Ta36Si14N50 thin film in the Si/Ta36Si14N50 (120 nm)/Cu(500 nm) and in the Si/TiSi2(30 nm)/Ta36SiN50 (80 nm)/Cu(500 nm) metallization that break down only after annealing at 900 °C. The failure is induced by a premature crystallization of the Ta36Si14N50 alloy (whose crystallization temperature exceeds 1000 °C) when in contact with copper

Thermal oxidation of reactively sputtered amorphous W_(80)N_(20) films

The oxidation behavior of reactively sputtered amorphous tungsten nitride of composition W_(80)N_(20) was investigated in dry and wet oxidizing ambient in the temperature range of 450 °C–575 °C. A single WO_3 oxide phase is observed. The growth of the oxide follows a parabolic time dependence which is attributed to a process controlled by the diffusivity of the oxidant in the oxide. The oxidation process is thermally activated with an activation energy of 2.5 ± 0.05 eV for dry ambient and 2.35 ± 0.05 eV for wet ambient. The pre‐exponential factor of the reaction constant for dry ambient is 1.1×10^(21) Å^2/min; that for wet ambient is only about 10 times less and is equal to 1.3×10^(20) Å^2/min

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