Fluorine-based plasma processes

Fluorine-based plasmas are currently employed in microelectronics industry for etching processes of metal (W), semiconductors (Si, Ge), or dielectrics (Si02, Si3N4). Mechanistic studies have shown that the key parameters of the plasma-surface inter-... 

Photoirradiation of this stacked film causes the Ag to diffuse into the Se-Ge film in a process referred to as Ag-photodoping. This diffusion, which is characteristic of amorphous chalcogenide materials, causes the Se-Ge film to become insoluble in alkaline solutions and the resist thus functions as a negative-type photoresist. The photodoped regions also are resistant to fluorine-based plasmas enabling dry development of the resist (7). Dry development has also been achieved using a reactive-ion etching (RIE) technique and is discussed later. 

Fluorine contamination has been reported in various environments and applications in the past. It has shown up in plasma processing [10-18], as crosscontamination from storage in contaminated containers or with contaminated samples [14,18], and modification of aluminum deposited on fluoropolymer substrates and other polymers having fluorine-based plasma treatments has also been observed [19-21]. Fluorocarbon lubricants have also been noted to modify the oxide structures on aluminum alloys [22,23], and the degradation of AI2O3 catalytic supports has been associated with fluoride conversion during reactions with fluorocarbons [24]. Alloy oxide modification has also been well noted in the presence of fluorine compounds not of the fluorocarbon family [25]. 

This can be accomplished by using materials between the metal lines that have a lower dielectric constant (also referred to as the k-value). Copper interconnect was first introduced with silicon oxide as the dielectric material, with a dielectric constant of about 4.0 (the value depends on the specifics of the deposition process, such as the precursor used, the temperature of deposition, plasma parameters, etc.). Substitution of some of oxygen atoms with fluorine in fluorinated silicon glass decreased the dielectric constant (with values about 3.7, depending on the fluorine content and process parameters). It should be noted that the incorporation of fluorine was not an unalloyed benefit, since the addition of greater amounts of fluorine can affect the moisture stability of the F-doped oxide films, and the F can attack Ta-based diffusion barriers. 

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