Biased Dual Magnetron Sputtering

BDMS is based on side-to-side, or face-to-face, dual magnetron sputtering (DMS) that is typically used with mid-frequency ac, in the range 10-100 kHz, which is provided by a floating power supply. In DMS, none of the two power supply terminals is connected to ground, and, as a rule, a conductive substrate is connected either to ground or kept floating from both ground and the power supply. No control of the electrical biasing of the substrate against the plasma is provided.

Figure 1: Schematic of dual magnetron sputtering system without (a) and with (b) substrate connection to the center tap.

BDMS is using a novel dual magnetron and substrate circuitry, which provides control of the substrate biasing voltage (Figure 1). The biasing voltage controls the energy delivered to the growing film, and thus the film properties. In BDMS, the two magnetrons are connected, as usual, to the ends of the secondary coil of an isolation transformer, while a conductive substrate holder is connected to the center tap of the secondary coil. The last connection is done through a resistor and/or an additional floating biasing power supply. BDMS was tested by deposition of dense, crystalline and corrosion resistant Al2O3 films on Al surfaces. Depositions were made using closed-loop control, based on the plasma optical emission, with high deposition rates of about 50-60 % of the metallic rate.

For more details contact Abe Belkind (abebelk@aol.com)

References:
1. A. Belkind, S. Song, G. McDonough, and R. Scholl, Biased Dual Magnetron Sputter Deposition of Alumina, in: 45th Annual Technical Conference Proceeding, Lake Buena Vista, 2002 (Society of Vacuum Coaters, 2002), p. 184.
2. A. Belkind, A. Freilich, G. Song, and Z. Zhao, Mid-Frequency Reactive Sputtering of Dielectrics: Al2O3, Surface and Coating Technology, 174-175 (2003) 88.