Solid-State Amorphization in a Ti/B Multilayer

Thin films of pure crystalline metals, that have a negative heat of mixing, are known to amorphize. Solid-state amorphization reactions are possible to study using multilayered structures. The amorphization reaction is typically observed in multilayered structures in which one layer of the pair is crystalline and the adjacent layer or interface is amorphous, as in Ni/Zr and Cu/Y. The reaction progresses via a low temperature isothermal anneal (at several hundred degrees centigrade) in which one species preferentially diffuses into the other. Recently, in-situ observation of solid-state amorphization in a completely crystalline Ni/Ti multilayer indicates that nucleation of the amorphous phase occurs at incoherent crystalline interlayer boundaries. (The completely crystalline as-deposited structure was achieved by ensuring thermalization of the sputtered neutrals.) The progression of solidstate amorphization in Ti-B is examined using the multilayered configuration.

In-situ observation of solid-state amorphization in a Ni/Ti multilayer

Solid-state amorphization between thin films of two pure crystalline metals that have a negative heat of mixing is shown by Schwartz. An isothermal anneal is used to amorphize a binary crystalline structure via interdiffusion of one species, preferentially into the other. We report a metallic-glass formation by solid state amorphization in a Ni/Ti multilayered structure by low temperature annealing in the electron microscope. TEM allows us to view the composition modulation and interfaces of the Ni/Ti multilayered structure in crossection. Crossectional TEM is regularly used to view the composition modulation and interfaces of thin films. A TEM fitted with a hot-stage sample holder makes it possible to heat the cross-sectioned multilayer in-situ and record the ensuing reaction at the Ni-Ti interfaces.Ni/Ti multilayers with a period of 26 nm (55 at.pct. Ni) were fabricated by magnetron sputtering, the details and parameters are outlined elsewhere. TEM specimens were prepared for cross-section viewing with a technique similar to Bravman and Sinclair, in combination with encapsulating the epoxied pieces with in a metal tube as described by Newcomb, et al.

Hydrogen Segregation at the Al/Si Interface Studied Using a Nuclear Resonant Reaction

Hydrogen segregation at the interface between an epitaxial Al film and a Si (111) substrate is studied using the 1H(15N, αγ)12C nuclear resonant reaction. Hydrogen depth profiles show that H atoms diffuse through the 1600 Å thick Al layer during 500 eV H implantation and are trapped at the Al/Si interface. The total amount of interface H is about 2 × 1015 /cm2 after a 1.4 × 1018 H/cm2 implantation, and the H atoms are narrowly distributed in the direction normal to the interface. During an isothermal anneal at 360 K, the amount of interface H decreases exponentially with annealing time; and during ramp annealing from 110 to 500 K, an abrupt release of the interface H is observed at temperature around 380 K. The release rates in both cases are controlled by a first order thermally activated de-trapping process with a binding energy of 0.86 eV/atom.

Millisecond Duration Annealing of Boron Implants in Silicon

ABSTRACTA dual electron beam machine has been used to anneal boron implanted layers in order to study the diffusion and activation behaviour over a wide range of doses. The annealed implants have been characterized by spreading resistance profiling and secondary ion mass spectroscopy (SIMS). Carrier concentration profiles show that millisecond duration anneals can activate boron implants. A boron dose of 1E16 ions/cm2 was annealed to give a sheet resistance of 30 Ωsq with 40% of the implant activated. The SIMS technique showed there were no significant differences between the atomic profiles of the as-implanted samples and specimens subjected to a millisecond anneal or to a low temperature 850°C rapid isothermal anneal for 10s.

Comparison of Isothermal Anneal Techniques for be or Si Implanted S.I. InP

ABSTRACTThis paper presents a study of the annealing of Be and Si implants into InP. It compares rapid thermal anneal (RTA) and furnace anneal (FA) techniques over a temperature range of 600-;900° C. The results demonstrate that RTA results in activation and mobilities as good as those obtained by FA for both Si and Be implant. The background Fe concentration of S.I. InP substrates lead to substantial differences in activation. Arrhenius fit of optimal activation data of Si indicates an activation energy of 1.8 eV. The Si implants display no redistribution during either type of annealing, while the Be implants display more than one type of redistribution. Moreover, the complete description of the Be redistribution requires the knowledge of both the atomic and the electronic profiles. Capless annealing eliminates the additional processing steps of capping but it also sets a limit on the maximum temperature and time of the annealing.

Formation of Shallow P+ Junctions Using Two-Step Anneals

ABSTRACTShallow (0.15-0.2 μm deep) p+ junctions have been formed using boron implanted into silicon which was pre-amorphized using a silicon implant. The implants were annealed using a two-step process; initially the wafers were furnace annealed at 600 °C for 100 min., followed by a rapid isothermal anneal (RIA) at 950-1100 °C for 10 sec. For comparison, some wafers were only given a single-step rapid isothermal anneal at 950-1100 °C for 10 sec. The shallowest junctions were formed when the amorphous silicon layer was deeper than the boron implant, because of the suppression of channelling. When the amorphous/crystalline interface was shallower than the tail of the boron implant, some channeling occurred. This channeling tail exhibited an enhanced diffusion during the single-step RIA which was reduced significantly by the two-step anneal. When the amorphous layer was deeper than the boron implant, the single-step and two-step anneals gave identical results.

A Comparison of Millisecond Annealing of B Implants and Isothermal Annealing for Times of a Few Seconds

ABSTRACTThe annealing behaviour of B implants in the millisecond time regime using a combination of swept line beam and background heating is compared with isothermal annealing with heating cycles of a few seconds. Carrier concentration profiles derived from spreading resistance measurements show that under annealing conditions which restrict diffusion, millisecond processing gives higher activation of B implants than isothermal heating. Transmission electron microscopy shows that millisecond annealing also results in a lower defect density than that following an equivalent isothermal anneal.