Increasing applications of chemical vapour deposited (CVD) diamond have raised the need for efficient and robust microwave plasma reactors which are optimized for the large area deposition of diamond films and wafers. On the basis of extended numerical simulations Fraunhofer IAF has developed a novel microwave plasma CVD technology. An ellipsoidal cavity is used to focus the microwave energy into an intense and extended plasma. These ellipsoidal plasma reactors exhibit a combination of beneficial properties including

• Large area deposition: homogeneous deposition of CVD diamond on 3" (2.45 GHz) and 6" (915 MHz) substrates possible. 

• Stability: Long-term operation possible, no plasma instabilities. 

• Versatility: The reactor can be run under various conditions (pressure, power etc.). 

• Growth of high-purity diamond: Properties of CVD diamond disks are identical to those of perfect single diamond crystals. 

This patented reactor technology has been successfully commercialized. The two figures show ellipsoidal plasma reactors which are fully computer controlled and equipped with all the safety units necessary for the operation in an industrial environment. The reactors are operated at 2.45 GHz, 6 kW (upper figure) and 915 MHz, 30-60 kW (lower figure), respectively.