Full Face Erosion Magnetron Cathodes (FFE)

The FFE is a unique and powerfully tool for the high rate deposition of sputtered layers with high traget use. It is also capable of overcoming many of the traditional difficulties experienced when performing high rate reactive deposition. At the same time it improves the ecconomics of the production process by allowing easy and control fast process control and tailored film properties.

Gencoa Full Face Erosion (FFE) Source is designed specifically to sputter the full target face even in reactive deposition mode and offers outstanding process advantages in terms of rate, target use, coating crystallinity / smoothness and ease of reactive gas control.

The Full Face Erosion (FFE) source is available in circular and rectangular forms with both an external or internal mounting style. A particularly powerful combination is to use two rectangular FFE cathodes side by side as a double magnetron for the reactive deposition of dielectric films. The combination of electron movement over the target and between targets has been shown to offer advantages for film growth. The FFE offers very high target use, 45% - 60% due to the scanning nature of the magnetic field. Consequently there are no re-deposit areas on the target surface which aids the reactive deposition of compounds and also defect reduction. But that tells only part of the story! Researchers at MMU and Liverpool Universities in the UK at the SVC08 in Chicago illustrated a number of other startling benefits (see download for full presentation):

Elimination of the Hysteresis effect in reactive sputtering

The researchers worked with a double rectangular FFE source and have discovered that as the speed of the scanning is increased to 300 rpm the usual hysteresis effect disappears and there is a linear transition of reactive gas partial pressure with flow in the TiO2 system. This eliminates the need for feedback control as any position on the line can be attained with the usual gas metering. Also, as the target is remaining in a metallic state, there rates are not reduced as there is no target poisoning.

Smoother films with faster plasma scanning

Typically for reactive processes the target poisoning can contribute to micro-arcs as the surface state of the target surface is partially metallic and partially a compound. The nature of compound on the surface can also be electrically insulating in the case of many oxide processes. Hence, portions of the target are electrically conducting and other areas electrically insulating. This is overcome by using pulsed DC or AC power to discharge the target surface during each cycle, but with the FFE source as the target remains metallic, the discharging is easier to achieve and hence the probablity of an arc is lower.

Other observations of film quality is that the coating growth is smoother with a higher speed of plasma scanning. The mechanism is not fully explained, but could be realted to enahanced plasma densities as the electrons are moved around and between the targets at higher and higher speeds. Please see the rectangular FFE page for more details and the MMU presentation available as a download.