Molten Target Sputtering (MTS) Deposition

A key difference in design between a conventional sputtering gun and the MTS gun seems very minor, but the ring-shaped groove between magnets allows for trapping a portion of magnetic field within the groove. A trapped field creates an additive force to expel the ionized particles (atoms and molecules combined within plasma) by increasing their kinetic energy. The ring groove also serves to increase the target material temperature because the conduction passage of thermal energy to the water-cooled copper sink is interrupted by the empty space of a ring groove below the target. Accordingly, the target surface material is heated to a higher temperature, which in turn increases the flux density by more easily liberating the atoms from the target. The MTS enables the growth of high quality thin (<100nm) and thick (>100m) films with the molten target and plasma. The degree of precise formation of rhombohedral film structures on a sapphire substrate is greatly improved. This leads to higher quality crystals with higher yield. In conventional techniques a pre-processor is required to elevate the sapphire wafer temperature through a 2-4 hour thermal soak process. These high temperatures, typically 890 deg. C, are costly and burdensome in a production facility. The MTS process can enable the sputtering temperatures to operate at 500 deg. C and still produce superior quality films.