We present a method for the simulation of the kinetic evolution in the sub µs timescale for composite materials containing regions occupied by alloys, compounds, and mixtures belonging to the Ni-Si-C ternary system. Pulsed laser irradiation (pulses of the order of 100 ns) promotes this evolution. The simulation approach is formulated in the framework of the phase-field theory and it consists of a system of coupled non-linear partial differential equations (PDEs), which considers as variables the following fields: the laser electro-magnetic field, the temperature, the phase-field and the material (Ni, Si, C, C clusters and Ni-silicides) densities. The model integrates a large set of materials and reaction parameters which could also self-consistently depend on the model variables. A parameter calibration is also proposed, specifically suited for the wavelength of a widely used class of excimer lasers (? = 308 nm). The model is implemented on a proprietary laser annealing technology computer-aided design (TCAD) tool based on the finite element method (FEM). This integration allows, in principle, numerical solutions in systems of any dimension. Here we discuss the complex simulation trend in the one-dimensional case, considering as a starting state, thin films on 4H-SiC substrates, i.e., a configuration reproducing a technologically relevant case study. Simulations as a function of the laser energy density show an articulated scenario, also induced by the variables’ dependency of the materials’ parameters, for the non-melting, partial-melting and full-melting process conditions. The simulation results are validated by post-process experimental analyses of the microstructure and composition of the irradiated samples.

We investigated the complex interaction between a nickel layer and a 4H-SiC substrate under UVlaser irradiation since the early stages of the atomic inter-diffusion. An exhaustive description is still lacking in the literature. A multimethod approach based on Transmission Electron Microscopy, Energy Dispersive Spectroscopy and Diffraction (electron and X-ray) techniques has been implemented for a cross-correlated description of the final state of the contact after laser irradiation. They detailed the stoichiometry and the lattice structure of each phase formed as well as the Ni/Si alloy profile along the contact for laser fluences in the range 2.4-3.8 J/cm 2. To make a bridge between process conditions and post-process characterizations, time dependent ultra-fast phenomena (laser pulse ≈160ns), such as intermixing driven melting and Ni-silicides reactions, have been simulated by a modified phase fields approach in the proper many-compounds formulation. We disclose that raising laser fluence has multiple effects: 1) the thickness of the silicide layer formed at the interface with 4H-SiC expands; 2) the silicon content into the reacted layer increases; 3) a Ni 2 Si phase is promoted at the highest fluence 3.8 J/cm 2 ; 4) silicon atomic diffusion into a topmost residual nickel layer occurs, with the Ni/Si ratio increasing towards the contact surface.

The dry etching of cobalt suicide has been investigated to evaluate the most important process variables. It has been demonstrated that among the commonly used etchants, only chlorine atoms are suitable to react appreciably with CoSi2. Strong ion bombardments and high temperatures are necessary to obtain good etch rates and to initiate the process (a resistant surface contaminant layer must be removed). A detailed XPS investigation of CoSi2 before and during the etching process is also reported. InfroductionThe resistivity of a polycide gate structure, i.e. suicide on polysilicon, is controlled by the suicide layer. A 1000 A thick tungsten sUicide deposited by chemical vapor deposition (CVD) on polysilicon, for instance, after annealing at 1000°C, has a sheet resistance 20-50 times lower than the same thickness of undoped polysilicon. In order to further reduce the resistivity of the polycide gate structure, CoSi2 and TiSi2 can be utilized in place of tungsten silicides. These are very promising materials both for their low resistivity and since they can be conveniently obtained by thermal sinterization of the metal sputtered on a polysilicon layer. This is a self-aligned process because the sili-COfltrofl,r

Multilayer metallizations play a very important role as interconnection systems in the VLSI technology. Here, to realize etching with good dimensional control and vertical profile, plasma etchers (of the RIE type) are used. The complexity of the chemistry involved in this plasma etching is such that it may give rise to some undesirable secondary effects. The object of this work is the surface characterization, by means of XPS, SEM, and EDAX techniques, of the A1/Si-Ti/W system after plasma etching. The chemical modifications induced by various plasma treatments of the metal films have been followed by means of the above techniques. Such modifications are dependent either on the etch chemistry used or on the substrate chemical species exposed to the plasma.Very large scale integration (VLSI) technology requires increasing the chip size and decreasing the minimum feature size. This objective is achieved by continuous developments in lithographic and etching techniques and by improvements in materials technology. The materials used for the interconnections can be metals, heavily doped polysilicon, and metal polycides. In general the main properties required for these materials are: low resistivity, good chemical and high temperature resistance, good barrier properties, low contact resistance, good step coverage, resistance to electromigration, and ease of patterning.Aluminum is the most widely used metal for interconnections in integrated circuits thanks to its many good properties such as low resistivity, excellent substrate adhesion, and ease of deposition and patterning. At the same time, aluminum has some important limitations: bad temperature resistance, hillock formation, and moreover it has the tendency to interact with silicon causing the "spikes" problem (spikes can penetrate into the silicon and cause shorts). In order to avoid this phenomenon, Al-alloy (1) is currently employed. A1/Si alloy reduces the silicon diffusion problem, but the possible precipitation of silicon at the metal-silicon interface after the alloy thermal process causes an increase in the contact resistance. A1/Si/Cu alloy has low resistivity and good resistance to electromigration, but it still has some problems: poor high-temperature resistance and hillock formation (as well as A1 and A1/Si) and, mainly, difficult patternability by dry etch for corrosion problems (2).In this context the use of refractory metals and their silicides represents an improvement, mainly in solving the contact problem. In general the refractory metals have higher resistivity than A1, but they have very good performances as the diffusion barrier between A1 and Si, and form at the same time good ohmic contacts and/or good Schottky contacts. Ti (3), W (4), and Ti/W (5) are among the most studied of these materials.Therefore a metallization that is constituted of a layer of refractory metal on the contacts under a layer of an A1 alloy as interconnection material can be considered an excellent solution.Pattern definition for VLSI circuits requires the use of dry ...