RF power is required when an electrically insulating ceramic target is used (e.g. Al₂O₃ or SiO₂). The RF power oscillates the electrons in the plasma at high speed and sets-up a negative self-bias on the electrically floating target surface. This negative self-bias is enough to accelerate the argon ions from the plasma and sputter the target material. Gencoa manufacture specialist DC and RF diodes (see plasma image right) as well as RF magnetron devices.

Each Gencoa standard design of rectangular cathode for DC or RF  has a minimum of 10mm insulator wall thickness and a minimum of 20mm surface insulation. This ensures that insulator break down is prevented in DC, pulsed DC, AC and RF power modes. In addition, there is NO part at a negative potential passing from the earthed rear plate to the live front cathode (some other manufacturuers use screws at potential with insulating covers - this is a point of weakness especially with RF power).

So the basic design of Gencoa cathodes go a long way to satisfying the high demands for RF applications. In addition to the standard insulation thickness, on RF cathodes a Faraday Cage type of construction is used for stable load matching. The RF power is distributed via a copper strip from the matching unit to a copper cage contacting the main cathode body at all points round the source. There is a uniform spacing between the cahode and earthed enclosure and only materials of high surface conduction are used. Water cooling of the rear plate removed heat from the in-vacuum anode - important for the high energy RF plasmas. On request, a cooling tube can be added directly to the in-vacuum anode structure.

Allowance is made in the rear box design for mounting of an RF matching unit of the customers choice. The rear enclosure and matching connection is RF sealed. The front of the cathode where it mates to the chamber is also RF sealed. On request Gencoa can recommend and integrate the RF matching unit before delivery. In adidition, the RF matching can be tuned at Gencoa under the plasma load with the customers target of choice.
For cathode operating with DC pulsed power and AC (medium frequency) power, some of the RF design practises are followed - the power is distributed uniformly around the cathode from the single cable input to a copper distribution plate the full length of the cathode, and then to the cathode itself via multiple high conductivity contact points. This reduces the possibility of standing-waves and plasma concentrations - esspecially important for large area cathodes.

The Faraday cage design of these RF cathodes mean that they can be used in multi-cathode systems and in face to face configurations with the appropriate phase shifters to provide stable and uniform operating conditions.