No abstract

A kinetic model for diffusional growth of silicides in thin-metal-film–silicon systems is proposed. The time dependence of the growth has been shown to be a function of the morphology of the growing silicide and the controlling diffusion process (diffusion in the film, interface diffusion). If the phase grows only in depth the parabolic dependence of silicide thickness h on time t in most cases follows the relation h≂t0.5. If silicide grows only in width w, then w≂t. In the case of simultaneous change of thickness and width when h/w=const the growth is proportional to t0.33.

Amorphous Ni-Nb alloys are of potential interest as diffusion barriers for high temperature metallization for VLSI. In the present work amorphous Ni-Nb films were sputter deposited on Si(100) and their interaction with a substrate was studied in the temperature range (200-700)°C. The crystallization of films was observed on the plan-view specimens heated in-situ in Philips-400ST microscope. Cross-sectional objects were prepared to study the structure of interfaces.The crystallization temperature of Ni5 0 Ni5 0 and Ni8 0 Nb2 0 films was found to be equal to 675°C and 525°C correspondingly. The crystallization of Ni5 0 Ni5 0 films is followed by the formation of Ni6Nb7 and Ni3Nb nucleus. Ni8 0Nb2 0 films crystallise with the formation of Ni and Ni3Nb crystals. No interaction of both films with Si substrate was observed on plan-view specimens up to 700°C, that is due to the barrier action of the native SiO2 layer.

Reactions of thin policrystalline Ni and amorphous Ni—Nb films with a Si (100) substrate in the temperature range of 200 to 770°C are studied by TEM, SEM, AES, and EDX methods. The crystallization of the Ni—Nb films is observed in‐situ in the TEM. The interaction of the Ni—Nb films with the substrate occurs above the crystallization temperature of the films and is found to be dependent on the heating rate. The reactions are accompanied by a phase separation process and the formation of large Ni silicide islands inside the substrate. No reaction of Ni films with Si is observed up to 650°C in the presence of a native SiO2 layer at the interface. An action of the stress gradients in Ni—Nb films and the corresponding formation of pinholes in the underlying native SiO2 layer is proposed to explain the results obtained.