The reaction of thin metal films with single crystal or amorphous silicon to form silicide compounds has been successfully undertaken using both scanned-cw and pulsed beam processing. Similar to the case for beam annealing of ion-implanted semiconductors, both the basic mechanisms and the experimental results are found to depend on whether pulsed or scanned beams are used to promote the reactions. For both cases the experimental results are often found to differ sharply from those obtained with standard furnace processing. For the pulsed beam reaction, melting and rapid resolidification occurs in the metal silicon films. The principal result is that the reacted film is frozen in a mixed phase compound which can consist of several silicide compounds including silicon and metal precipitation. Compositions inaccessible by conventional furnace annealing can also be formed by this process. In contrast to the pulsed beam results, scanned-cw beam processing of metal silicon films is found to result in the formation of large area uniform silicide phases with essentially no silicon or metal precipitation. These films are generally found to be homogeneous with well defined silicon/silicide interfaces.

Theoretical and experimental studies on the laser annealing of a Si/CoSi2/Si structure are presented. The power absorption in each layer in this structure is theoretically considered using the refractive index and extinction coefficient in CoSi2 and Si, which have been measured by the ellipsometric analysis. Next, an amorphous Si film deposited onto a Si(lll)/CoSi2 structure is annealed by a Q-switched ruby laser. It has been shown from Rutherford backscattering and channeling measurements that the Si film grows epitaxially onto the Si/CoSi2 structure and that an optimum power density to minimize the aligned yield in a Si film 100 nm thick exists around 1.5 J/cm2. Reflecticn electron diffraction and otpical ricroscope analyses are also used to check the crystalline quality and surface structures of the laser-annealed samples.

We have investigated the post-irradiation annealing effects of laser-formed Pt, Pd, Rh and Ni-silicides. It was found from Rutherford backscattering and x-ray analysis that compositional changes occur during subsequent high temperature annealing in a vacuum furnace. Generally, a single silicide phase tends to form at the expense of the other phases present following laser irradiation. The surviving phase is not necessarily identical to the end-phase found in a binary solid-state reaction couple of the same system.

Raman scattering and Rutherford backscattering are used to study the products of SEM processing of Pd and Pt thin films on Si(100) substrates. The RBS measurements indicate the compositional depth profile of the resulting silicide while the Raman scattering indicates the crystal structure. For both cases it is found that the resultant silicide is dominated by Pd2 Si (or Pt2Si) structures but evidence of deviations are also noted.

Pulsed beams (laser, electron, or ion) and ion beams (ion beam mixing) have been used to induce structural and compositional changes in metal-metal and metal-semiconductor thin-film structures. Metastable crystalline and amorphous phases have been formed. Although ultra fast quenching occurs with both techniques, metastable phases are formed by quenching from the liquid with pulsed beams and from the solid-phase with ion-induced reactions. With both techniques metastable phases can be formed over a broader compositional range than with conventional melt-quench methods.

Q-Switch laser pulses are used to convert vapor-deposited metal-Si thin films into the amorphous state by a melting, mixing and quenching process. Experimental findings obtained with the metals Au, Pt, Pd, V and Nb are presented and compared with results from a numerical simulation of the laser induced melting and quenching process.

Pulsed ruby laser irradiation of unimplanted single crystal and implanted polycrystalline Al has been studied with ion beam analysis and TEM. The results show that Al is melted to a depth of ∼ 0.9 μm with a 4.2 J/cm2 , 15 nsec pulse, and that vacancies are quenched into Al during resolidification. Diffusion of Zn in liquid Al is observed, and a melt time of ∼ 65 nsec is estimated for a 3.8 J/cm2, 30 nsec pulse. The observations are in reasonable agreement with calculations of sample temperature and melt times. We observe no precipitation of AlSb in liquid Al for Sbimplanted Al, and conclude that the nucleation time satisfies 50 nsec ≲ tnuc ≲ 200 nsec. We find no evidence for amorphous Al after irradiation of single crystal Al with energies ≳ 1.5 J/cm2.

The formation of metastable alloys by pulsed electron beam annealing of Al implanted with Sn or Ni and of Si implanted with Sn has been studied by TEM, ion backscattering and channeling. Surface segregation after pulsed melting is observed in Si but not in Al, even though all impurities have similar equilibrium distribution coefficients of∼10-2. This difference is attributed to the higher liquid-solid interface velocity and lower diffusivities in Al. Metastable substitutional solutions more than an order of magnitude above equilibrium solubilities are obtained for Ni and Sn in Al. At Ni concentrations ∼ 5 at.% a highly disordered transformation zone is formed in Al and a new phenomenon in which a polycrystalline layer forms on epitaxially regrown Al is observed.

Surface layers of Ni crystals have been melted with Q-switched Nd-YAG laser radiation. The epitaxially regrown surface layers show significant differences between 〈100〉 and 〈111〉 crystals cut from the same boule. The 〈100〉 crystals exhibit a dislocation cell structure with a dislocation density of l011 - 1012 cm-2. The 〈111〉 crystals contain a laterally uniform dislocation network resulting in a much higher dislocation density for the 〈111〉 surface. The elements Ag, Au, Pd, Sn and Ta have been implanted into Ni single crystals at surface concentrations of up to 20 at %. All the as- implanted systems demonstrate solid solubility. We have used these implanted systems to study the alloys formed by laser melting of Ni. In all systems, with the exception of Ag, 100% of the atoms are trapped on lattice sites.

Laser pulse melted single crystals of several metals have been examined by the Rutherford backscattering/channeling technique and with optical and scanning electron microscopy. Metals belonging to the three major structure groups; fcc (Ni, Pd, Rh); bcc(Mo, Nb, W, Fe); and hcp (Be, Ti, Re) have been studied at various laser power levels and in different crystallographic orientations. Of these cases, Be, Ti and Fe show high temperature allotropes which are expected to influence the character of the resolidified surface layer.

The melt phase alloying of Ni-Au films on Ni substrates has been studied for rapid quenches following 35 nano-second Q switched ruby laser pulses (0.69μ wavelength) in the energy regime of 0.5 to 3.0 j/cm2. The Ni and Au films were each 200 Å in thickness having been deposited on a polished Ni substrate by standard hot ribbon vapor deposition methods. Data was obtained on pre and post alloyed surface layers using Rutherford backscattering, transmission electron microscopy, and STEM energy dispersive X-ray analysis. The melting and resolidification dynamics of the liquid-solid interface was monitored through finite difference integration of the non-linear heat conduction equation to give temperature profiles, depth of melting and melt front velocities associated with the liquid-solid phase change. Resolidification velocities were typically 15 meters/second with melt depths extending to a few thousand angstroms depending on pulse energy. RBS data confirms that liquid phase diffusion of gold in nickel has occured. TEM analysis reveals the presence of a two phase mixture being composed of nickel rich and gold rich material. Microbeam energy dispersive X-ray analysis indicates the presence of a relatively uniform mixing of these two Phases. Pronounced one dimensional solute segregation was not observed in these specimens, however, overall penetration depths of the gold was somewhat larger for the lower energy densities than for the larger ones. Also, unusual circular cell patterns were observed in the resolidified material, their contrast being enhanced by preferential etching during the TEM specimen polishing procedure.

Pulsed laser annealing has been evaluated as a technique for fabricating superconducting V3 Si from multilayer V-Si samples, and the nature of laser-induced defects in V3 Si single crystals has been examined. Correlated analyses by ion scattering, ion channeling, Tc measurements and TEM were used to examine the composition and structure of samples subjected to single and multiple laser pulses. It was observed that although the superconducting A15 phase could be formed by pulsed laser mixing, the associated rapid quenching effects introduced defects which were not completely removed by thermal annealing to 925 K for 1 hour. Ion channeling and TEM studies of V3 Si single crystals showed that pulsed laser irradiation caused microcracks to develop in the surface, probably from mechanical stresses induced by thermal gradients.

Mechanisms involved in laser processing of ion implanted semiconductors have been extensively investigated (1,2). Relatively little work has been done on implanted metals (3,10). The liquid solid interface (melt front) velocity in metals (11,12) is much larger than that in Si. Therefore several nonequilibrium effects on recrystallization (6) solute segregation (9) and metastable phase formation (4,6,7) are observed. Such effects would depend on the melt front velocity, equilibrium phase diagram considerations (such as equilibrium segregation coefficient Ko, miscibility in licuid phase, intermediate phases etc.) and also on the as implanted nonequilibrium phase and defect structure. In this paper we present a study of the influence of some of these parameters during laser treatment of sincle crystals of virgin Al and dilute implanted alloys of Mo and Cd in Al.