The crystallization of a‐Si in a‐Si (50‐nm) and Au (5‐nm) thin‐film bilayers has been investigated during heat treatment in a transmission electron microscope. When crystallization of a‐Si first begins at 130 °C, the Au‐Si alloy (Au and a precursor phase) reflections observed at lower temperatures vanish, and several new reflections from metastable Au‐Si compounds occur. Dendritically growing islands of poly‐Si are observed after heating at 175 °C. If the samples are held at a constant temperature of 175 °C for 10 min, the poly‐Si islands coalesce. The formation of poly‐Si depends on the diffusion of Au into a‐Si and the formation of metastable Au‐Si compounds, which act as transport phases for both Si and Au. After crystallization Au segregates to the front and back surfaces of the poly‐Si film. The result of this work and earlier diffraction investigations are interpreted in terms of superlattices based on a sublattice. A fundamental body‐centered‐cubic structure with a=5.52 A and composition Au4Si is s...

Crystallization of amorphous silicon during thin-film gold reaction

The Au−Si (Gold-Silicon) system

The Au‐Si interactions on the backside of 〈111〉 silicon wafers have been studied over the temperature range of 275–400 °C by transmission electron microscopy. The Au films annealed at temperatures below the Au‐Si eutectic temperature (363 °C) all have similar structure—columnar Au grains of small size (∼450 A). An orthorhombic gold silicide, Au3Si, forms at the Au/Si interface below the eutectic temperature due to the migration of Au into the silicon substrate. The Au3Si grains are of much larger size (∼2000 A) than Au and contain twins. Annealing at 400 °C, which is above the eutectic temperature, results in a completely different structure. It consists of numerous small Si islands protruded and dispersed throughout a continuous, large grain (>2.8 μm), polycrystalline gold film. Gold silicide was not observed at 400 °C. Many Au grains are found to grow epitaxially on the silicon substrate. The silicon islands are also found to grow epitaxially on silicon substrate. The structure after 400 °C annealing is...

Transmission electron microscopy of gold‐silicon interactions on the backside of silicon wafers

The crystalline silicide layers formed on (111) and (100) surfaces of Au films on various Si single-crystal substrates are studied by LEED and AES in conjunction with sputter-depth profiling as a function of annealing temperature. On the (111) surface, three basic silicide structures are obtained corresponding to layers of various thicknesses as obtained by different preparation conditions. The (100) surface shows only two different structures. None of the structures is compatible with the various bulk silicide structures deduced from X-ray diffraction. Using LEED as a criterion for the presence or absence of silicide on the surface, smaller layer thicknesses are obtained than reported previously on the basis of AES studies.

Silicide surface phases on gold

Low-energy electron-loss spectroscopy and Auger-electron-spectroscopy studies of noble-metal—silicon interfaces: Si-Au system

: Investigations were conducted on solid-solid reactions in gold films evaporated on silicon substrates at deposition temperatures below the eutectic point (370 C). Both air- and vacuum-annealed structures were studied using correlated data from transmission electron microscopy/diffraction (TEM/TED), Auger electron spectroscopy (AES) profiling, and forward current-voltage (I-V) measurements. Results of these experiments show that the grain size in Au films deposited (or annealed) at temperatures from 25 C to 200 C increases from 50 anstrom (min) to saturation size of approximately 1 micro m at temperatures greater than 150 C.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA051170&Location=U2&doc=GetTRDoc.pdf

J. Peng

Papers

Investigation of solid–solid reactions of Au films on silicon