Christian Lavoie

Towards implementation of a nickel silicide process for CMOS technologies

In this paper, we review some of the advantages and disadvantages of nickel silicide as a material for the electrical contacts to the source, drain and gate of current and future CMOS devices. We first present some of the limitations imposed on the current cobalt silicide process because of the constant scaling, of the introduction of new substrate geometries (i.e. thin silicon on insulator) and of the modifications to the substrate material (i.e. SiGe). We then discuss the advantages of NiSi and for each of the CoSi2 limitations, we point out why Ni is believed to be superior from the point of view of material properties, miscibility of phases and formation mechanisms. Discussion follows on the expected limitations of NiSi and some of the possible solutions to palliate these limitations.

Metal-gate FinFET and fully-depleted SOI devices using total gate silicidation

Metal-gate FinFET and FDSOI devices were fabricated using total gate silicidation. Devices satisfy the following metal-gate technology requirements: ideal mobility, low gate leakage, high transconductance, competitive I/sub on//I/sub off/, and adjustable V/sub t/. Six silicide gate materials are presented, as well as two silicide workfunction engineering methods.

An off-normal fibre-like texture in thin films on single-crystal substrates

In the context of materials science, texture describes the statistical distribution of grain orientations. It is an important characteristic of the microstructure of polycrystalline films, determining various electrical, magnetic and mechanical properties. Three types of texture component are usually distinguished in thin films: random texture, when grains have no preferred orientation; fibre texture, for which one crystallographic axis of the film is parallel to the substrate normal, while there is a rotational degree of freedom around the fibre axis; and epitaxial alignment (or in-plane texture) on single-crystal substrates, where an in-plane alignment fixes all three axes of the grain with respect to the substrate. Here we report a fourth type of texture—which we call axiotaxy—identified from complex but symmetrical patterns of lines on diffraction pole figures for thin films formed by solid-state reactions. The texture is characterized by the alignment of planes in the film and substrate that share the same d-spacing. This preferred alignment of planes across the interface manifests itself as a fibre texture lying off-normal to the sample surface, with the fibre axis perpendicular to certain planes in the substrate. This texture forms because it results in an interface, which is periodic in one dimension, preserved independently of interfacial curvature. This new type of preferred orientation may be the dominant type of texture for a wide class of materials and crystal structures.

Diffusion barrier properties of transition metal thin films grown by plasma-enhanced atomic-layer deposition

Ta thin films were grown on Si(001) and polycrystalline Si substrates by plasma-enhanced atomic-layer deposition (PE-ALD) using TaCl5 and atomic hydrogen as precursors. The grown films have resistivity of 150–180 μm cm with a small Cl concentration between 0.5 and 2 at. %. The diffusion barrier properties were investigated using bilayer structures consisting of 200 nm Cu deposited by sputtering on ALD Ta films with various thicknesses. Three in situ analysis techniques consisting of x-ray diffraction, elastic light scattering, and resistance analysis were used to determine the diffusion barrier failure temperature of Ta films. The barriers were annealed at a temperature ramp rate of 3 °C/s from 100 to 1000 °C in forming gas. For this method using x-ray diffraction, the barrier failure temperatures were determined by monitoring the disappearance of the Cu(111) x-ray diffraction peak and appearance of Cu silicide diffraction peaks. At the diffusion barrier failure temperature, elastic light scattering indic...

High-temperature degradation of NiSi films: Agglomeration versus NiSi2 nucleation

The thermodynamical and morphological stability of NiSi thin films has been investigated for layers of thickness ranging from 10to60nm formed on either silicon-on-insulator (SOI), polycrystalline silicon, or preannealed polycrystalline silicon substrates. The stability of the films was evaluated using in situ x-ray-diffraction, sheet resistance, and laser light-scattering measurements. For NiSi films that are thinner than 20nm, agglomeration is the main degradation mechanism. For thicker films, the agglomeration of NiSi and nucleation of NiSi2 occur simultaneously, and both degradation mechanisms influence each other. Significant differences were observed in the degradation of the NiSi formed on different substrates. Surprisingly, agglomeration is worse on SOI substrates than on poly-Si substrates, suggesting that the texture of the NiSi film plays an important role in the agglomeration process. As expected, preannealing of the polycrystalline silicon substrate prior to metal deposition results in a signi...

In situ x-ray diffraction study of metal induced crystallization of amorphous germanium

Metal induced crystallization (MIC) is a technique that lowers the crystallization temperature of amorphous semiconductors. The process has mainly been used to influence the crystallization of amorphous silicon (a-Si) and multiple studies on this subject have already been performed. The research of the MIC of amorphous Ge (a-Ge) has been mostly limited to the use of a Ni or Al film. This paper focuses on the characterization of the crystallization behavior of a-Ge films in the presence of 20 transition metals (Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, and Al). The kinetics of the crystallization process are also systematically studied for the seven metals that lower the initial crystallization temperature the most. In addition, the influence of the thickness of the metal film was determined for the case of a Au and Al film. A comparison of the influence of the various metals on a-Ge and a-Si is made and the similarities and differences are discussed using existing models for the MIC process.

Sharp Reduction of Contact Resistivities by Effective Schottky Barrier Lowering With Silicides as Diffusion Sources

An extremely low contact resistivity of 6-7 × 10^-9 Ω·cm² between Ni_0.9Pt_0.1Si and heavily doped Si is achieved through Schottky barrier engineering by dopant segregation. In this scheme, the implantation of B or As is performed into silicide followed by a low-temperature drive-in anneal. Reduction of effective Schottky barrier height is manifested in the elimination of nonlinearities in IV characteristics.

Influence of Pt addition on the texture of NiSi on Si(001)

We report on the texture of Ni1−xPtxSi films on Si(001) substrates. X-ray diffraction measurements in Bragg–Brentano geometry appear to indicate that pure NiSi films are randomly oriented, while the addition of Pt was reported to induce an epitaxial alignment. However, detailed texture analysis using pole figure measurements shows that pure NiSi films are in fact strongly textured. The NiSi grains exhibit five different types of preferential orientation. The addition of an increasing amount of Pt gradually changes these five texture components. This texture evolution can be understood on the basis of the expansion of the monosilicide unit cell, caused by the incorporation of Pt.

Low temperature formation of C54–TiSi2 using titanium alloys

We demonstrate that the temperature at which the C49 TiSi2 phase transforms to the C54 TiSi2 phase can be lowered more than 100 °C by alloying Ti with small amounts of Mo, Ta, or Nb. Titanium alloy blanket films, containing from 1 to 20 at. % Mo, Ta, or Nb were deposited onto undoped polycrystalline Si substrates. The temperature at which the C49–C54 transformation occurs during annealing at constant ramp rate was determined by in situ sheet resistance and x-ray diffraction measurements. Tantalum and niobium additions reduce the transformation temperature without causing a large increase in resistivity of the resulting C54 TiSi2 phase, while Mo additions lead to a large increase in resistivity. Titanium tantalum alloys were also used to form C54 TiSi2 on isolated regions of arsenic doped Si(100) and polycrystalline Si having linewidths ranging from 0.13 to 0.56 μm. The C54 phase transformation temperature was lowered by over 100 °C for both the blanket and fine line samples. As the concentration of Mo, Ta...

Reaction of thin Ni films with Ge: Phase formation and texture

The solid-state reaction between a 30-nm-thick Ni film and Ge substrates was investigated using in situ x-ray diffraction, diffuse light scattering, and four-point probe electrical measurements. Our results reveal that Ni5Ge3 and NiGe appear consecutively on Ge(111) while they grow simultaneously on amorphous Ge(α-Ge) and Ge(001). Furthermore, phase formation temperatures depend strongly on the nature of the substrate being the lowest on α-Ge and the highest on Ge(111). X-ray pole figure measurements of the NiGe phase obtained from the reaction with an amorphous substrate indicate a completely random texture while several epitaxial and axiotaxial texture components are observed on both Ge(001) and Ge(111). The texturing for the NiGe film on Ge(111), which showed a sequential phase formation, is an order of magnitude more pronounced than for the film on Ge(001) which showed a simultaneous growth.