Marc-A. Nicolet

Epitaxial films of semiconducting FeSi2 on (001) silicon

Epitaxial thin films of the semiconducting transition metal silicide, beta‐FeSi2, were grown on (001) silicon wafers. The observed matching face relationship is FeSi2(100)/Si(001), with the azimuthal orientation being FeSi2[010]‖‖Si〈110〉. This heteroepitaxial relationship has a common unit mesh of 59 A2 area, with a mismatch of 2.1%. There is a strong tendency toward island formation within this heteroepitaxial system.

Properties of reactively sputter-deposited TaN thin films

Abstract We deposited Taue5f8N films by reactive r.f. sputtering from a Ta target with an N 2 ue5f8Ar gas mixture. Alloys over a composition range 0–60 at.% N have been synthesized. We report on their composition, structure and electrical resistivity before and after vacuum annealing in the temperature range 500–800 °C. We found that the film growth rate decreases with increasing ratio of the nitrogen flow rate to the total flow rate, while the nitrogen content in the films first increases with the N 2 partial flow rate and then saturates at about 60 at.%. B.c.c.-Ta, Ta 2 N, TaN and Ta 5 N 6 appear in succession as the nitrogen content rises, with Ta 2 N being the only single-phase film obtained. The atomic density of the films generally increases with the nitrogen content in the film. Transmission electron micrographs show that the grain size decreases from about 25 to 4 nm as the nitrogen concentration increases from 20 to 50 at.%. The Ta 2 N phase can exist over a wide range of nitrogen concentration from about 25 to 45 at.%. For as-deposited films an amorphous phase exists along with polycrystalline Ta 2 N in the center portion of that range. This phase crystallizes after vacuum annealing at 600 °C for 65 min. A diagram of stable and metastable phases for Taue5f8N films based on X-ray diffraction and transmission electron microscopy results is constructed. The resistivity is below 0.3 m ohms cm for films with 0–50 at.% N and changes little upon vacuum annealing at 800 °C.

Formation and Characterization of Transition-Metal Silicides

Publisher Summary This chapter focuses on formation and characterization of transition-metal silicides. Many deposition techniques can be applied to form thin silicide layers on very large-scale integration (VLSI) structures. The common methods are vacuum evaporation with filament or e-gun, sputtering, and chemical vapor deposition. The silicon for the silicide may be drawn from the silicon substrate in a subsequent metal-silicon reaction, in which case a metal film only is deposited. Modern methods of analysis of thin films are mainly based on the detection of beams that are emitted from or scattered by the film as a result of irradiation by a primary incident beam. Several transition metal silicides have been identified as semiconductors. The relatively high resistivity of these silicides and the ability to vary the resistivity and the thermal coefficient of resistance makes these materials attractive for thin-film resistors.

Ternary amorphous metallic thin films as diffusion barriers for Cu metallization

Abstract The novel field of ternary amorphous metallic thin films made of an early transition metal and a combination of B, C, N, Si, and P is briefly reviewed. Ternary alloys composed of a transition metal, silicon, and nitrogen applied as thin-film diffusion barriers for Cu contacts to Si devices are emphasized. The synthesis of these films by reactive sputtering is described, their structural and electrical properties are discussed, and the reason for their unique performance as diffusion barriers for copper are explained. Shallow junction diodes provided with a 10 nm thick barrier layer of this type and a copper overlayer can withstand 650°C for 30 min in vaccum without significant degradation of the reverse current. A table lists all diode tests published so far in the open literature.

Ti-Si-N diffusion barriers between silicon and copper

Thin films of Ti-Si-N, reactively spattered from a Ti/sub 5/Si/sub 3/ target, are assessed as diffusion barriers between silicon substrates and copper overlayers. By tests on shallow-junction diodes, a 100 nm Ti/sub 34/Si/sub 23/N/sub 43/ barrier is able to prevent copper from reaching the silicon substrate during a 850/spl deg/C/30 min anneal in vacuum. A 10 nm film prevents diffusion up to 650/spl deg/C/30 min. By high-resolution transmission electron microscopy, Ti/sub 34/Si/sub 23/N/sub 43/ predominantly consists of nanophase TiN grains roughly 2 nm in size.<<ETX>>

Thermal Oxidation of Reactively Sputtered Titanium Nitride and Hafnium Nitride Films

The oxidation behavior of reactively sputtered and thin films was investigated for oxide formation in dry and wet oxidizing ambient in the temperature range of 425°–800°C. For both cases, formation of a single‐oxide phase, rutile for oxidized and monoclinic for oxidized , was observed. The oxidation process is thermally activated, and it has a parabolic time dependence, except in the case of wet oxidized where nonuniform oxidation behavior was observed. The parabolic time dependence of the oxide growth is attributed to a transport‐controlled process which is limited by the diffusivity of the oxidant in the oxide. The dry oxidation of is much faster than the dry oxidation of at a given temperature. The oxidation rate is always higher in a wet than in a dry ambient.

Thermal Stability of Hafnium and Titanium Nitride Diffusion Barriers in Multilayer Contacts to Silicon

Etude de la stabilite thermique des couches de HfN et TiN pour leur application comme barrieres de diffusion dans les contacts electriques. La stabilite thermique depend des proprietes mecaniques des couches et donc de la methode de depot

Epitaxial CoSi2 films on Si(100) by solid‐phase reaction

The inversion of a bilayer of Co on top of Ti and a Si(100) substrate upon steady‐state annealing, and the resultant formation of an epitaxial CoSi2 layer have been studied using both reactive (N2, N2+5% H2, He+14% H2) and nonreactive (vacuum) annealing ambients. In nitrogen, a high‐quality, single‐crystalline CoSi2 layer forms above 600u2009°C for 30 min, with an abrupt interface to the substrate. As the fraction of hydrogen in the ambient increases, the abruptness of the interface deteriorates slightly. On top of this silicide, the Ti is chemically bound with oxygen present as a contaminant. In the case of a nonreactive annealing ambient, the Co/Ti inversion still takes place, although it is only partial. Moreover, the interface is very rough. The structure is unstable above 800u2009°C for 30 min annealing and transforms into a mixed layer of Co0.25Ti0.75Si2 and epitaxial CoSi2 grains. Using isothermal vacuum annealings with varying durations, a square‐root time dependence is observed for the growth of the epit...

Damage and strain in epitaxial GexSi1–x films irradiated with Si

The damage and strain induced by irradiation of both relaxed and pseudomorphic GexSi1–x films on Si(100) with 100 keV 28Si ions at room temperature have been studied by MeV 4He channeling spectrometry and x-ray double-crystal diffractometry. The ion energy was chosen to confine the major damage to the films. The results are compared with experiments for room temprature Si irradiation of Si(100) and Ge(100). The maximum relative damage created in low-Ge content films studied here (x=10%, 13%, 15%, 20%, and 22%) is considerably higher than the values obtained by interpolating between the results for relative damage in Si-irradiated single crystal Si and Ge. This, together with other facts, indicates that a relatively small fraction of Ge in Si has a significant stabilizing effect on the retained damage generated by room-temperature irradiation with Si ions. The damage induced by irradiation produces positive perpendicular strain in GexSi1–x, which superimposes on the intrinsic positive perpendicular strain of the pseudomorphic or partially relaxed films. In all of the cases studied here, the induced maximum perpendicular strain and the maximum relative damage initially increase slowly with the dose, but start to rise at an accelerated rate above a threshold value of ~0.15% and 15%, respectively, until the samples are amorphized. The pre-existing pseudomorphic strain in the GexSi1–x film does not significantly influence the maximum relative damage created by Si ion irradiation for all doses and x values. The relationship between the induced maximum perpendicular strain and the maximum relative damage differs from that found in bulk Si(100) and Ge(100).

WNx: Properties and applications

Abstract The deposition rate, composition, resistivity, and intrinsic stress of r.f. sputter- deposited WN x films have been investigated in detail as functions of various sputtering parameters. We have also evaluated the diffusion barrier performance of WN x films in three different contact schemes to silicon and GaAs. Finally, a possible application of a Ti/WN x bilayer to the self-aligned TiSi 2 process is discussed.