Paper EN-TuP7
High Quality TCO Deposition using New DC Power Supplies

Tuesday, October 21, 2008, 6:30 pm, Room Hall D

The main application of magnetron sputter processes for thin film solar cell production is the deposition of transparent conductive oxides (TCO). The most significant example for this TCO material class is ZnO:Al (AZO) which is of great importance as a transparent conductive layer for photovoltaic applications. Since this material has an especially high arcing rate, pulsed DC power processes have been used for deposition in the past. A new DC power supply family has been developed with the goal of replacing these pulsed DC processes with economic standard DC processes. The most important feature of this power supply is an extremely fast and advanced arc management with the capability to run stable processes with high arcing rates. The arc management has three different detection criteria: a voltage, a current and a combined voltage/current criteria. After detecting an arc, a positive voltage is applied to the cable between the power supply and cathode. This so-called Cable Length Compensation compensates the stored energy of the cable and reduces the energy supplied into the arc after power shut off. In this way residual arc energies of less than 0.5 mJ/kW, are achievable. Stable processes over a long time with arcing rates of up to 20,000 arcs/s become possible. The fast arc management with adaptable parameters results in superior film quality, and homogeneity of the deposited film. The new economic DC power supplies replace pulsed DC power without any disadvantages.