Low Temperature Reactions at Si-Metal Contacts –From SiO2 Growth due to Si–Au Reaction to the Mechanism of Silicide Formation

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Abstract
When Si is in contact with metal film, it readily reacts at low temperatures (≤200°C) leading to several interesting effects. For example, thick (∼1000 Å) SiO2 growth for a short time (∼10 min) due to Si–Au reaction and uniform silicide layer formations at Si/Pd, Pt, Ni interfaces. Since Si is a typical covalent semiconductor with high melting point (∼1400°C), without the presence of such effect of metal to weaken the covalent bond of Si adjacent to the metal, the above reactions rarely occur. As a possible mechanism of the bond-weakening, the present author proposes a model postulating electronic screening of Coulomb interaction responsible for the covalent bonding due to mobile free electrons in the metal films. This “Screening model” seems to be evidenced through observations of initial stages of Si-Au and -Pd reaction by both electron and ion scattering spectroscopies. In addition, new usage of the channeling effect of MeV He+ ions is demonstrated to be a powerful tool for interface and surface studies.