High-purity Refractory Metals for Thin Film Metallization of VLSI

It is shown that cast targets of highly pure refractory metals like W, Mo, Ti, Ta, Co, etc. and their compounds can be produced by means of a set of vacuum-metallurgical techniques—by vacuum high-frequency levitation, EB floating zone melting, EB melting, and electric arc vacuum melting as well as chemical purifying by ion exchange and halides. The cast refractory metal targets are extremely pure and chemically homogeneous. For magnetron sputtering and laser ablation, the cast silicide targets are also produced. The study reveals the possibilities and conditions of depositing the silicides and titanium-tungsten barrier layers by both the laser evaporation and magnetron sputtering. The physical and structural parameters as well as a trace impurity composition of sputtered metals and deposited thin films are studied by grazing-beam incidence X-ray diffraction, Auger electron spectroscopy, Rutherford backscattering of helium ions, mass spectrometry with inductively coupled plasma, etc

Electromagnetic Levitation of Metal Melts

The main advantage that attracted the attention of researchers was the lack of contact of liquid metal with refractory lining, which ensured the elimination of one of the main sources of metal contamination by such a harmful impurity, such as oxygen. This is especially important for melting refractory and highly reactive metals and semiconductors. Compared to other melting methods, which also ensured the absence of contact of liquid metal with the crucible (vacuum arc, electron beam floating zone, cold crucible, plasma, etc.), EML of metal melts has a number of significant advantages. Among all types of noncontact technologies, only EML has the functions of levitation and heating

Work function dependent neutralization of low-energy noble gas ions

The work function dependence of the neutralization of low-energy He+, Ne+, and Ar+ ions was studied by determining the neutralization probability of ions scattered from submonolayer coverages of Ba on W(110) and Re(0001) substrates. At high work functions (>3.5 eV), it was found that the dominant neutralization mechanism for noble gas ions with initial energy between 2 and 5 keV scattering from Ba is collision-induced neutralization. The neutralization probability for this mechanism was found to be insensitive to work function changes. We argue that collision-induced neutralization is also the dominant charge transfer process for scattering from other earth-alkali and alkali elements in this energy range, although at lower energies it is expected that Auger neutralization will become important. At work functions below roughly 3.5 eV, resonant neutralization to the first excited level of the noble gas ions occurs in addition to the charge transfer processes operating at high work functions. We show that the additional neutralization at low work functions can be described using resonant charge exchange theory. Due to resonant neutralization, the neutralization probability for noble gas ions increases exponentially with decreasing work function

Work function dependent neutralization of low-energy noble gas ions

The work function dependence of the neutralization of low-energy He+, Ne+, and Ar+ ions was studied by determining the neutralization probability of ions scattered from submonolayer coverages of Ba on W(110) and Re(0001) substrates. At high work functions (>3.5 eV), it was found that the dominant neutralization mechanism for noble gas ions with initial energy between 2 and 5 keV scattering from Ba is collision-induced neutralization. The neutralization probability for this mechanism was found to be insensitive to work function changes. We argue that collision-induced neutralization is also the dominant charge transfer process for scattering from other earth-alkali and alkali elements in this energy range, although at lower energies it is expected that Auger neutralization will become important. At work functions below roughly 3.5 eV, resonant neutralization to the first excited level of the noble gas ions occurs in addition to the charge transfer processes operating at high work functions. We show that the additional neutralization at low work functions can be described using resonant charge exchange theory. Due to resonant neutralization, the neutralization probability for noble gas ions increases exponentially with decreasing work function