New arc management system

No matter if it is in semiconductors or photovoltaics, the coating technology used on flat panel displays or architectural glass - wherever thin coatings are required - plasma coating is the preferred choice. However, the application of thin layers inside a plasma chamber is susceptible to electric discharges called arcs that can severely disturb the coating process. A new arc switch currently under development by HÜTTINGER Elektronik assists power supplies to more quickly detect arcs and therefore, suppress them more efficiently.

Plasma-based coating processes employ a mixture of gases to create plasma inside a vacuum chamber. Chemical reactions take place within the plasma. The resulting products of this reaction are deposited as a thin layer on the substrate. Often, and without any warning, arc strikes occur between the electrodes. These arcs can damage the coating layers that have been applied as well as the material that is being sprayed. Arcs typically appear 40 to 50 times per second, but in extreme cases, they can occur several thousand times per second. To protect the substrate, i.e. the surface that is being coated, the power supply, needs to detect arcing as fast as possible, so that the energy input can be interrupted and the discharge extinguished.

To detect arcs, an integrated electronic detector monitors the incoming electric current and voltage applied to the plasma inside the processing chamber. When a sudden drop in voltage and an increase in current beyond a set limit occurs, one should assume that an arc is occurring. In this case, the energy supply to the process is interrupted by deactivating the generator. However, the power supply cannot shut off its output instantaneously. Even after being shut off, the generator will supply some residual energy to the plasma chamber, sustaining the discharge. A few microseconds can pass before the arc is completely extinguished, and this short time span can be sufficient to cause significant damages.