This invention applies to the field of sputtering, depositing SiGe thin films on sapphire substrates. It is a method of modifying the film growth front, enabling epitaxially grown heterostructure devices at lower temperatures and with higher purity, avoiding the conventional time required (2 hours) and high-energy-consumption thermal soaking at a high temperature (800 °C.) Less than 500 °C is enough to grow the single-crystal Si1-xGex (x=0.85) film because much higher-kinetic-energy molecules reach the substrate.
The Molten Target Sputtering (MTS) method can increase the kinetic energy, the energy latency, and the flux density of sputtered atoms by combining the benefits of both magnetron sputtering and evaporation systems. It does this by a mechanical modification to the magnetron sputtering gun. For the MTS method, only a 1~2-mm (depth and width) ring-shape groove is cut between the magnets in order to keep a gap between the copper plate and the sputtering target (see figure). This effectively increases the efficiency of magnetron-based sputtering machines. The ring enhances the magnetic field intensity and increases the temperature of the target material.
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.