The amorphous to crystalline transformation of Ge in Al/Ge thin film couples has been studied using glancing angle EXAFS, x-ray reflectivity and diffraction. It was found that crystallization occurs at a much lower temperature (118-150 °C) than for bulk Ge, and initiates at the Al/Ge interface. X-ray diffraction studies were made at 152 °C to study the kinetics of the reaction. After an initial period we find good agreement with a square root dependence of the time, characteristic of a diffusion limited reaction.

High Resolution Electron Microscopy (HREM) and image calculations are combined to study microstructural changes related to the CoSi/Si-CoSi/CoSi2/Si-CoSi2/Si transformations. The samples are prepared by UHV e-beam evaporation of Co layers (2 nm) followed by annealing at 300°C or 400°C. Cross-sectional observations at an atomic scale show that the silicidation of Co at the lower temperature yields epitaxial CoSi/Si domains such that [111]Si // [111]CoSi and <110>Si // <112>CoSi. At about 400°C CoSi2 nucleates at the CoSi/Si interface. During the early stages of this chemical reaction, an epitaxial CoSi/CoSi2/Si system is observed. The predominant orientation is such that (021) CoSi planes are parallel to (220) CoSi2 planes, the CoSi2/Si interface being of type B. The growth of CoSi2 is shown to proceed at the expense of both CoSi and Si.

Coalescence and microstructure of buried CoSi2 layers formed by 100 keV Co+ implantation at 350°C into Si(111) are studied. Doses ranged from 1×1016 to 1.6×l017 cm−2. The critical dose (dc) required to form a continuous layer is found to be the same, 1.1±0.1×l017 cm−2, in both (111) and (001) substrates, despite pronounced differences in precipitate morphology. Three types of precipitates are observed in Si(111) during the mesotaxial process: A–type (fully aligned), B0–type (twinned on the (111) plane parallel to the surface), and B1,2,3–type (twinned on one of the three (111) planes inclined to the surface). The fraction of each varies with both the implantation and annealing conditions. Formation of a continuous, twinned (B0–type), buried layer after 1000°C annealing is shown to be possible for the first time by this synthesis technique in samples implanted at dc.

The epitaxy and morphology of TiSi2 on Si(l 11) are studied as a function of Ti thickness. Titanium thicknesses of 1–2 monolayers and Ti films with thicknesses of 50Å; were examined. The titanium silicide films were formed on atomically clean Si substrates by ultrahigh vacuum (UHV) deposition of Ti followed by in situ annealing. In situ LEED and AES measurements characterized the reaction process. For room temperature deposition of less than two monolayers of Ti the LEED pattern associated with the reconstructed substrate disappeared, and the 1×1 bulk pattern also disappeared completely. Annealing at 200°C resulted in a decrease in the Ti AES signal indicating interdiffusion. For annealing up to 500°C, a series of changes in the LEED patterns were observed, which indicated that the disordered layer transformed to an ordered surface layer. Annealing to higher temperature resulted in the reappearance of the diffraction pattern associated with the 7×7 reconstructed Si(111) surface. This indicated three dimensional island growth. For the TiSi2 formed by in situ annealing of 50Å of Ti on Si(111), three different types of island morphologies were observed and identified as the C49 phase of TiSi2. The C49 TiSi2 was proven to be an epitaxial titanium silicideby HRTEM and SAD. Two different orientation relationships of the TiSi2 islands are found: 1) [3 1 1] C49 TiSi2 // [112]Si and (130) C49 TiSi2 //(11 1) Si, and 2) [1 1 2] C49 TiSi2 // [110] Si and (021) C49 TiSi2 //(1 11) Si. The C49 nucleation and island morphologies are discussed in terms of the character of the epitaxial interface.

Titanium nitride, formed either by rapid thermal processing (RTP) or reactive sputtering, is commonly applied as a barrier film in the fabrication of metal-to-substrate contacts for CMOS devices. In one approach a titanium film is sputtered onto a patterned dielectric and then nitrided at a temperature greater than 500° C to form a TiN layer. Variations in the structure and resistivity of the titanium layer are observed when the titanium overlies a borophosphosilicate glass (BPSG) film. The structural change appears as a “wrinkling” of the TiN film and the TiN/BPSG interface. More severely wrinkled films are characterized by lower sheet resistivities. Results of TEM and SEM analyses are presented, as well as data on TiN resistivity and reflectance for nitridation temperatures in the range 650°C to 900°C, and for BPSG boron and phosphorus concentrations of approximately 3 to 5 wt. %. Mechanisms for the TiN wrinkling are discussed.

The growth and microstructural evolution of Al/Ni and Ni/AI bilayer thin films have been investigated as a function of Al and Ni layer thickness and thermal treatment by transmission electron microscopy. Studies were also made of Al and Ni single layers of varying thickness. All films were grown by dc magnetron sputtering using carbon coated Cu TEM grids as substrates. For the bilayers, the Al thickness was fixed at either 3.5 or 7.0 nm while the Ni thickness was varied systematically from 3.2 to 12.8 nm. Deposition sequence significantly influenced bilayer microstructure even in as-deposited samples. Al/Ni bilayers generally exhibited a finer microstructure than Ni/AI. In the 3.5 nm Al/Ni bilayers no conclusive electron diffraction evidence was found for elemental Al while for the reverse sequence both Al and NiAl3 diffraction rings were found. In the 7.0 nm Al/Ni bilayers diffraction rings due to Al were observed. The reverse sequence again produced both Al and NiAl3 diffraction rings. Interestingly, diffraction rings due to the Ni layers were found for all samples but were consistently measured at positions corresponding to a 2.5–3.5% increase in interplanar spacing. Annealing at 385°C produced evidence for generalized grain growth and strong accentuation of the electron diffraction rings due to the NiAl3 phase. Again, deposition significantly influenced annealed bilayer microstructure. For the Al/Ni sequence annealing produced polycrystalline N1AI3 island-like structures, while for Ni/AI bilayers, annealing promoted the growth of small NiAl3 crystals uniformly distributed in the film.

Using magnetically enhanced dc-triode sputtering we have grown metallic multilayers of Ag/Pd and Cu/Pd with modulation wavelengths A ranging from 10 Å to 120 Å. The Ag/Pd films were prepared with two different thickness ratios of silver to palladium (1:1 and 3:1) while the Cu/Pd films all were 1:1. We observed in the Ag/Pd films that the variation with A of the (111) lattice spacing dav in the growth direction is less than 0.5%, independent of the composition. However, these films exhibited enhancements in the Rayleigh sound velocity vR of up to 22% for the 1:1 samples and 13% for the 3:1 Ag/Pd samples respectively as A decreased. The Cu/Pd films showed a slight systematic dependence of dav on A, although its variation was only approximately 0.7%. A softening in vR of up to 7% for the Cu/Pd samples was observed.

A series of Cu/C and CuNi/C multilayer films are prepared for potential use as normal incidence x-ray reflectors. The use of a metal alloy layer is intended to enhance layer formation without metastable metallic carbide formation. The films are characterized both in composition and structure. Addition of Ni to the Cu-rich layer is seen to markedly improve the formation of continuous metal layers.

We report the application of diffuse light scattering to study buried interface reactions. As a model system we discuss the annealing of thin Cu/Al bilayers. Samples were prepared by evaporating Cu/Al and Al/Cu bilayers onto SiO2 covered Si wafers at room temperature. The Cu-Al thickness ratio was chosen to yield an average composition of CuAIt. When bilayers are annealed at 200–250°C the scattering intensity increases by about a factor of five above the as-deposited samples. We believe that this increase is partially due to the non-uniform reaction at the Cu/Al interface and partially to the mottled surface formed when leading growing parts of the reaction layer reach the surface. The relative contribution from this scattering mechanism is discussed quantitatively. For higher annealing temperature(300–350°C) the scattered light intensity falls again almost to the original level, suggesting that the Al/Cu reaction is complete and that the surface is homogeneous and smooth. For higher temperature anneals (400–500°C) the scattering once again increases, mainly due to the natural monotonic increase in surface roughness when metals are annealed. Control samples of the pure metal on Si02 show only the high temperature roughening effect.

The effect of heat treatments on the microstrueture, composition and electrical properties of the Al/TiW/ Polycrystal1ine Si system was studied systematically for the first time. It was found that Al and Si diffuse through the grain boundaries of the TiW layer at 400°C. Subsequently, Si accumulates at the Al/TiW interface while Al diffuses into the po1ycrystal1ine Si. TiSi, TiSi2, Al3Ti, and WAl10 are formed only at the Al/TiW interface as a result of the heat-treatments for 30min at temperatures between 450 and 500°C. The sheet resistance, measured on the surface of the Al film, is constant up to 350°C and then increases with the heat treatment temperature at all times. The I–V curves are characteristic to Schottky diodes. The general dependece of the current on the applied voltage remains the same but the electrical resistance changes as a result of the heat-treatments. At the long annealing time(30min), the electrical resistance decreases with the heat-treatment temperature. However, at the short annealing times(10–60sec), it first incrsases(between 400 and 450°C) and then decreases (between 450 and 500°C). The results of the electrical measurements are correlated to the microstructural and compositional changes occured due to the heat treatments.

The interactions between Pt thin films and In53Ga47As have been studied. An important result is that the reaction kinetics deviate from those of other metal/compound semiconductor reactions. The kinetics can be divided into two stages, where the reaction slows by a factor of 5 after ~60 minutes of annealing at 400°C. In addition, Auger depth-profiling indicates that an In-rich layer develops at the reacted layer/substrate interface.

The interfacial reactions between thin films of Co and single crystal InP have been studied. The reaction between the Co and the InP substrate already start in the as-deposited state to form In and P rich compounds. During annealing at 250°C for 30 min., phase separation takes place. In addition to unreacted Co, we find Co rich compounds, a Co-P compound in contact with the substrate, and Co-In compound in contact with the metal layer. The general morphology appears to be stable up to 500°C. At higher temperatures (500–600°C) P is released from the substrate. CoP4, Co2P, CoIn2 and In were detected by X-ray diffraction. At this stage the reaction is no longer uniform.