Alwin Earl Michel

Transient boron diffusion in ion‐implanted crystalline and amorphous silicon

Boron diffusion in ion‐implanted and annealed single‐crystal and amorphized Si is compared to determine the effect of amorphization on the initial transient boron motion reported for single crystal. The boron was implanted at 20 keV and at doses of 1×1015 and 3×1015cm−2. The Si was either preamorphized or postamorphized to a depth of 320 nm by implantation of Si ions at three different energies. In the amorphized samples the entire boron profile was always contained within this distance. The samples were annealed by furnace or rapid thermal annealing to 900–1100 °C with or without a preanneal at 600 °C. The initial rapid diffusion transient in the tail region of the boron profile was observed in all the crystal samples. This transient was totally absent in the amorphized samples. This is manifest by careful comparison of boron concentration profiles determined by secondary ion mass spectrometry of single‐crystal and amorphized samples after annealing. For anneals where significant motion occurs, the profi...

Diffusion of Sb, Ga, Ge, and (As) in TiSi2

Gallium, Sb, and Ge were implanted into thick (about 400 nm) layers of TiSi2 prepared by metal‐silicon reaction. The diffusion of the implanted atoms was analyzed by means of secondary ion mass spectrometry. Gallium was introduced because a former study had shown that the usual p‐type dopant B does not diffuse in TiSi2. Germanium was used in lieu of a Si tracer. Its diffusion characteristics are compared to those of P and As (as well as Si) which had been investigated previously. Germanium and Ga diffuse readily above 600 °C, but Sb does not. Its diffusion appears to be limited to grain‐boundary effects. Accumulations of the diffusing atoms are observed (except for Sb) at the silicide‐silicon interface. These are due to kinetic effects, namely fast diffusion at grain boundaries and interfaces, rather than to real adsorption which is an equilibrium condition. Because diffusion in intermetallic compounds has been shown to be significantly affected by variations in stoichiometry, experiments were conducted w...

The diffusion of elements implanted in films of cobalt disilicide

The diffusion of several elements implanted into layers of CoSi2 with a nominal thickness of 800 nm, grown by metal‐silicon reaction, has been studied by secondary ion mass spectroscopy. Boron has by far the highest mobility. It is totally homogenized by heat treatment for 0.5 h at 800 °C; it displays evidence of grain‐boundary diffusion at 400 °C and of lattice diffusion at 450 °C. The next group of elements, gallium, phosphorus, and germanium (used as a tracer in lieu of a silicon isotope) diffuse distinctly less rapidly, and remain nonhomogenized after annealing at 800 °C. The lattice diffusion of arsenic and antimony is not detectable (by the means presently used), even after heat treatment at the same relatively high temperature. Low‐temperature effects, and effects far away from the implanted region, are dominated by grain‐boundary diffusion. The lattice diffusion increases from boron to phosphorus and germanium, with activation energies determined to be 2.0 and 2.7 eV for boron and phosphorus, resp...