Multi-cusp plasma sputter-type ion source for the formation of gallium nitride (GaN) thin film

Abstract

Different techniques have been used for the formation of GaN and other III-V nitride thin films. Among the popular methods include the Molecular Beam Epitaxy (MBE), Chemical Vapor Deposition (CVD), Metalorganic CVD and other hybrid plasma-assisted growth techniques. In MBE and CVD techniques, two methods can be used to produce nitrogen radicals: by using either nitrogen (N₂) plasma or by directly using ammonia (NH₃). As ammonia is highly toxic, use of N₂ plasma to produce GaN is more favorable in terms of its ease of use and safety. In one recent study, GaN and InN thick films were synthesized by saturating gallium and indium with atomic nitrogen supplied from a microwave plasma source at low pressure. Results indicated that the direct conversion of the nitrogen saturated Ga melts to the solid nitride produced thick GaN films. Meanwhile, films can also be formed by depositing plasma particles on a substrate.
Multi-cusp sputtering sources had been developed for the production of various negative ion species which are relevant to materials processing in areas such as ion implantation, film deposition, and ion beam etching. Mass selected ion production can also be made by chemical sputtering process where the production mechanism of the negative ions involved the emission of particle flux of the target material by sputtering. Similar multi-cusp ion source arrangements had also been successfully investigated in the production of He^- and H^-, respectively. In this study, a plasma-sputter ion source is used to prepare GaN films by plasma-assisted deposition.