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The usual Si dopants, B, P, As, and Sb, plus Ge were implanted into thick (400 nm) TiSi 2 layers deposited in an amorphous state by sputtering from a compound target. Samples with the various implants were annealed at temperatures from 300 to 700°C and analyzed both by transmission electron microscopy and secondary ion spectroscopy. The annealed samples display a very large grain size, which complicates the interpretation of the concentration profiles obtained by SIMS. In the case of a high dose of B (1 × 10 16 atoms/cm 2 at least), there is an indication of grain boundary transport occurring mostly in the initial stage of the heat treatments, followed by phenomena dominated by a reduced solubility in the terminal large-grained matrix. With all elements, except Sb, evidence of diffusion is obtained at 400°C. Germanium diffusion is even observed at 300°C.

Self-aligned formation of silicides allows selective formation of MSi 2 on poly- or mono-crystalline Si and is typically used for gate, source and drain metallization. Under certain conditions lateral growth of a parasitic layer is observed during silicide formation. For example, TiSi 2 formation under Ar atmosphere or in a vacuum results in a thin conductive layer on SiO 2 , which can expand over several microns in the neighbourhood of Si. In this paper results of experiments with WSi 2 and TiSi 2 formation will be presented. Different conditions have been investigated with respect to lateral growth: anneal under vacuum, Ar, N 2 or different dilutions of NH 3 , or deposition of an encapsulation layer on top of the metal prior to the anneal. Results of both silicides will be compared. Based on these experiments a model will be proposed for the fast diffusion which causes the lateral growth.

Dopants, mostly boron, but also arsenic and antimony, implanted in unannealed WSi2 films prepared by chemical vapor deposition diffuse quite readily at temperatures as low as 600°C. Complete homogenization in layers 200 nm thick is obtained at that temperature in periods of time less than 24 h. These results can be attributed to the large density of grain boundaries in layers that are initially amorphous and crystalline during the course of the diffusion annealings. They are in sharp contrast to what is observed when the layers are annealed at high temperature to cause grain growth and stabilization of the silicide structure prior to implantation. The dopants then are largely immobile not only at 600°C, but even during prolonged oxidation procedures at 800°C. Similar low temperature diffusion of boron in WSi2 had been observed earlier in bilayers of polysilicon and WSi2, but it is only presently that one is aware of the huge difference in diffusion behaviors between annealed and unannealed silicide layers.

For decreasing dimensions of PMOS devices, the standard N+-doped polysilicon gate “buried-channel” degrades rapidly with respect to the subthreshold current behaviour. Dual work function gate electrodes have been implemented in a 1 μm CMOS process. Dopant atoms were implanted into WSi2 simultaneously with the S/D implantation and subsequently diffused into the underlying polysilicon layer by RTA. By comparison with conventional n-type gate MOSFETs, it was verified that significantly improved subthreshold characteristics were obtained with p-type PMOS gate electrodes. But to obtain in this way dual silicided gates leads to an insurmountable problem of dopant lateral diffusion pointed out by VΓ shifts between isolated gates and common N/PMOS gates in inverters. This problem of lateral diffusion through the silicide has been avoided by using a different processing sequence. Indeed, with the conventional TiSi2 salicide process, dopants are implanted and activated before the silicidation and only a low temperature anneal is applied to the silicide. This thermal aspect seems to be the key point to obtain at the same time silicided and N+/P+ gates.

The reaction between W and Si forming tungsten silicide has been studied for boron implanted samples. It is shown that dopant implantation in the silicon layer strongly slows down the reaction. Boron diffusion towards the metal leads to a very sharp peak in the concentration in this layer. Decrease in growth rate can be justified by formation of stable tungsten boride compounds detected by X-ray diffraction. When boron is implanted in W, fast dopant redistribution through the whole metal layer occurs at low annealing temperatures. Small slowing down effects on the reaction are then observed.

Different mechanisms can result in vacancy formation in the active slip bands of crystals subjected to cyclic deformation. Measurements about the size and concentrations of the possible vacancy agglomerates or voids do not exist, however. Therefore, measurements of small-angle neutron scattering were done on undeformed and cyclically deformed copper single crystals of the orientation 〈111〉 and of a thickness of 4mm. The cyclically deformed crystals showed increased scattering, which, after fatigue to about 80% of the fatigue life, can be related partly to dislocations and partly to voids about 20 A (2 nm) in diameter. The corresponding value for the volume fraction is about 10 −5 . Measurements of positron annihilation on sections of the same crystals confirm these results.

The influence of electrically active n-type (75As) and p-type (11B) impurities on the solid phase epitaxial regrowth of ion-implanted amorphized Si and Ge has been studied for low temperature furnace annealing. Both types of impurity increase the rate of regrowth of both silicon and germanium at a concentration level of 1020 cm−3 . Above this level, 75As retards regrowth in germanium. In compensated surface layers, the regrowth rate slows down to the values observed in self-implanted or intrinsic crystals for both silicon and germanium. The results can be qualitatively explained in terms of electrically induced generation of point defects at the amorphous-crystalline interface.

The feasibility of a WSi 2 salicide process is shown. Lateral diffusion is well controlled using NH 3 ambient during RTA. Lateral isolation and the continuity of self-aligned MOSFET test structures with SiO 2 spacers were tested electrically.