Interactions in the Co/Si thin-film system. II. Diffusion-marker experiments

Gurp, G. J. van; Weg, W. F. van der; Sigurd, D.

doi:10.1063/1.325360

Cited by 125 publications

(18 citation statements)

References 20 publications

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“…The high-resolution image taken around the interface ͑shown on the right͒ further reveals that small islands ͑ϳ5 nm in size͒ of CoGe are barely connected with each other just underneath the interface between Co and Ge, the appearance of which suggests that Co atoms have probably diffused into the Ge substrate and subsequently reacted with Ge to form the CoGe phase, similarly to the well-known initial solid-state reaction of Co with Si. 15 The high-resolution image also shows the existence of a discrete, bright layer between the unreacted Co and CoGe, which is believed to be the segregation of oxygen swept out of the growing germanide. A similar observation was also reported in the Co/Si system due to the initial presence of oxygen at the Co/Si interface and within the Co film, and the low reduction capability of the Co film.…”

Section: Resultsmentioning

confidence: 96%

Microstructural Evolution and Electrical Characteristics of Co-Germanide Contacts on Ge

Park¹,

An²,

Lee³

et al. 2009

J. Electrochem. Soc.

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The microstructural evolution and corresponding electrical contact properties of Co-germanide systems were investigated. The Co-germanide formation process underwent several intermediate, high-resistive phases ͑CoGe and Co 5 Ge 7 ͒, while low-resistive CoGe 2 was formed over 650°C in a narrow process window of Ͻ100°C. Because of the strong Fermi level pinning effect, Co, CoGe, and Co 5 Ge 7 phases exhibited Schottky contact behaviors with similar Schottky barrier heights on n-type Ge and ohmic contact behavior on p-type Ge, respectively. However, for the CoGe 2 /n-type Ge contact formed at 700°C, a nearly ohmic contact behavior started to appear, which was attributed to the possible diffusion of Co atoms into the Ge substrate due to the hightemperature germanidation process.Recently, a variety of alternative channel materials having a high intrinsic carrier mobility, such as Ge and compound semiconductors, has been widely studied due to their potential to allow the speed of transistors to reach a level that is unattainable with the conventional Si substrate and to assist in the ongoing miniaturization of the devices. 1,2 Furthermore, the lack of stable grown-oxides of Ge and compound substrates has been overcome by the recent progressive development of the deposited high-k gate dielectrics that have replaced SiO 2 in metal oxide semiconductor field-effect transistor ͑MOSFET͒ devices, such as ZrO 2 , HfO 2 , and Hf-silicates. Although many process problems remain to be resolved, some devices fabricated based on high-k and alternative channel materials have demonstrated very promising electrical results. 2,3 With its high carrier mobility and excellent process compatibility with the current Si processing ͑compared to compound semiconductor͒, Ge is a very attractive possible candidate for the Si replacement.In Si-based MOSFETs, various metal silicides have been widely used as a contact material due to their low resistance, low-formation temperature, and good thermal stability to reduce the contact and parasitic resistance in source and drain regions. 4 Similarly, metal germanide appears as a natural candidate for Ge-based devices. The successful development of metal germanide as a contact material requires understanding the exact phase/microstructural evolution occurring during annealing of metal films on Ge and the corresponding electrical contact properties with p-or n-doped Ge substrates. Among many possible metal-germanide systems, the successful application of Ni-and Co-silicides in the Si-based technology has led researchers to target their corresponding germanides as promising candidates for contact materials in Ge-based devices.The phase evolution of Ni-and Co-germanides as a function of the formation temperatures has been carefully studied by many researchers, 5-8 and their Schottky diode properties were also reported. 5,9-12 However, only a few studies have focused on the Co/Ge system, 7,8,11 while the electrical contact properties on substrates with different doping types and various germanide phases rema...

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Section: Resultsmentioning

confidence: 96%

Microstructural Evolution and Electrical Characteristics of Co-Germanide Contacts on Ge

Park¹,

An²,

Lee³

et al. 2009

J. Electrochem. Soc.

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“…25 Previous studies showed that the growth of CoSi is diffusion limited. 26,27 Furthermore, marker experiments showed that Si is the dominant diffusing species. 28 For the diffusionlimited case, the growth of CoSi is governed principally by the diffusion of dominant diffusing species.…”

Section: Discussionmentioning

confidence: 99%

Formation and growth of CoSi2 on (001)Si inside 0.2–2 μm oxide openings prepared by electron-beam lithography

Yew

Chen

1999

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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The formation and growth of CoSi2 inside 0.2–2 μm linear oxide openings and contact holes prepared by electron-beam lithography have been investigated. A thin, uniform epitaxial CoSi2 was grown inside 0.5 μm or smaller linear openings and 0.7 μm or smaller contact holes by both one- and two-step rapid thermal annealing processes. On the other hand, epitaxial and polycrystalline CoSi2 were found to form on silicon near the edge and central region, respectively, inside 0.6 μm or larger linear openings. The size effect of the oxide openings is correlated to the distribution of local stress induced at the oxide edge. The formation of CoSi at low temperature appeared to be retarded by the local compressive stress near the edge of the linear oxide openings. The relative ease in the epitaxial growth of CoSi2 near the oxide edge of the linear openings and of 0.7 μm and smaller contact holes is attributed to the thinness of the CoSi layer.

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“…For instance, the Co 2 Si/Si interface will move into Si by Co atom motion since Co is the primary diffusing species [18].…”

Section: Discussionmentioning

confidence: 99%

In situ and Ex situ Measurements of Stress Evolution in the Cobalt-Silicon System

et al. 2000

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The biaxial stress in Co thin-films has been investigated in situ by measuring changes in substrate curvature that occurred during deposition and annealing. Films of Co, 35 to 500 nm in thickness, were deposited by UHV magnetron sputtering at room temperature on Si (100) and poly-Si substrates. Results show that during Co deposition the bending force increased linearly with film thickness; a signature of constant stress. In addition, the stress evolution during silicide formation was measured under constant heating rate conditions from room temperature up to 700 o C. The stress-temperature curve was correlated with Co 2 Si, CoSi, and CoSi 2 phase formation using in situ synchrotron X-ray diffraction measurements. The room temperature stress for the CoSi 2 phase was found to be ~0.8 GPa (tensile) in the films deposited on Si (100) and ~1 GPa (tensile) on the films deposited on poly-Si. The higher tensile stress in the poly-Si sample could be a result of Si grain growth during annealing. INTRODUCTIONCobalt silicide has been used to create low leakage junctions in sub-0.25 µm technologies [1]. Unlike Ti-silicide metallurgy, CoSi 2 forms easily in small structures as it does not exhibit polymorphism. In addition, CoSi 2 also has a slightly lower resistivity and forms at lower temperature than C54-TiSi 2 . A complete optimization of the Co-salicide process should include an understanding of the stress changes that arise during the reaction. The formation of high stresses during processing could introduce defects, such as dislocations, that would be a hindrance to device operation [2].The experimental measurement of the intrinsic stress in vapor-deposited polycrystalline and epitaxial thin films has been the subject of many investigations over the past several years. Less common, but of significant technological importance, is the understanding of the stress changes that occur during solid state reactions in thin-film systems. This topic has been the subject of two reviews by d'Heurle [3][4]. For silicides formed under isothermal conditions the stress has been modeled by considering the sum of the instantaneous forces applied to a substrate by the growth of a compound phase minus relaxation during the reaction [5].Under constant heating rate conditions, extrinsic stress arises from differences in thermal expansion coefficients between the film and substrate, while intrinsic stress changes can develop from the formation of possibly several compounds. This type of measurement can be used to investigate the formation of phases over a range of temperatures, and thus provide important insight into the nature of the stress changes throughout a reaction sequence.During isochronal annealing, Co will react with Si initially forming Co 2 Si at ~450 o C followed by CoSi at ~ 500 o C, and finally CoSi 2 at ~600 o C. Several previous studies have investigated the stress change during silicide formation on Si (100) [2,[6][7]. In this study, we present results describing the stress evolution of Co films during growth and subsequent a...

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Interactions in the Co/Si thin-film system. II. Diffusion-marker experiments

Cited by 125 publications

References 20 publications

Microstructural Evolution and Electrical Characteristics of Co-Germanide Contacts on Ge

Microstructural Evolution and Electrical Characteristics of Co-Germanide Contacts on Ge

Formation and growth of CoSi2 on (001)Si inside 0.2–2 μm oxide openings prepared by electron-beam lithography

In situ and Ex situ Measurements of Stress Evolution in the Cobalt-Silicon System

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