Choosing the right element
Until recently, graphite heaters have been used in the majority of deposition stages and are still the mainstay providing robust performance in UHV applications such as MBE. However, graphite heaters oxidise and are consumed when run in the presence of high partial pressures of O2 at high temperature.
For sputtering applications which involve high partial pressures of O2, other technologies are also available with superior performance.
Solid Silicon Carbide coated Graphite elements provide improved durability when using oxidising atmospheres by comparison with PgG. Being an insulating form of SiC, holes are required in the coating to make electrical connection and the underlying Graphite is exposed and vulnerable to oxidation at these locations.
Solid Silicon Carbide elements (see Figure 1) are manufactured from a conducting solid SiC material in the ß phase and are more robust in all respects. They are durable to mechanical or electrical shocking, reactive gas/oxidation immunity at temperature. They are also optimised to give the very best in temperature uniformity. By virtue of the large radiating surface to gap ratio, all these elements run at considerably lower temperatures than often used metal wire heaters which ensures heater longevity. The typical ratio of heated element surface to meander gap is >5:1 resulting in excellent substrate heating uniformity, even without rotation.