Dual Anode Sputtering

DAS is a new way to solve the anode problem through enhancement of the discharge at the anode in such a way that it runs in the "self-cleaning" regime. In this regime, the dielectric layer deposited on the anode is repeatedly (continuously) sputtered off. A self-cleaning DAS system consists of two anodes and a single magnetron, powered by an ac power supply (Figure 1).

Figure 1. Schematic of dual-anode single magnetron sputtering systems with substrate connection to the center tap.

Each of the anodes is connected to one side of a center tapped ac power source. The center point, or "tap", of the power supply, is connected to a single magnetron source. Depending upon the polarity of the ac power supply, the system works in such a way that each anode acts alternatively as a true anode (electron collector), or as a sputtered cathode (ion collector). The continuous reversal of voltage and current will also keep any insulating regions of an anode from charging, and therefore inhibit anode arcing. Further, charged areas of the target are discharged twice in each cycle, since the voltage across the transformer passes through zero.

In the case of a DAS, the substrate is connected to the cathode to provide a bias potential, through a resistor alone, and/or a with an additional bias power supply (Figure 1). If there is no resistor or additional power supply in the substrate circuitry (i.e., the substrate is connected directly to the cathode), the substrate works as an additional cathode, and the plasma density near the substrate determines the current through the substrate. A resistor in the substrate circuitry lowers the ion currents through it (and the voltage, and so the energy of the arriving ions), while a positive potential applied to the substrate attracts electrons for heating.

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

ABA's Publications and Presentations (for .pdf files contact Abe Belkind):

Papers:
1. R. Scholl, A. Belkind, and Z.Zhao, Anode Problems in Pulsed Power Reactive Sputtering of Dielectrics, in: 42nd Annual Technical Conference Proceedings, Chicago, 1999 (Society of Vacuum Coaters, 1999), p. 169.
2. A. Belkind, Z. Zhao, D. Carter, G. McDonough, G. Roche, and R. Scholl, Reactive Sputtering Using a Dual-Anode Magnetron System, in: 44th Annual Technical Conference Proceeding, Philadelphia, 2001 (Society of Vacuum Coaters, 2001), p. 130.
3. A. Belkind, Z. Zhao and R. Scholl, Dual-anode Magnetron Sputtering, Surf. Coat. Techn. 163 –164 (2003) 695.
4. A. Belkind, A. Freilich, G. Song, Z. Zhao, R. Scholl, and E. Bixon, Mid-frequency reactive sputtering of dielectrics: Al2O3,