Process development for large area diamond deposition by multi-filament CVD

One of the key issues for market introduction of CVD diamond technology is the economic fabrication of CVD diamond products. Consequently a lot of R&D work has been performed to reduce deposition costs by developing processes with higher growth rates and/or larger deposition areas. Beside microwave plasma CVD and arc jet CVD (HFCVD) process is a promising candidate for economic fabrication of CVD diamond products in different fields of application. Advantages of this technology are simplicity, low costs for a deposition system, the ability for coating substrates with complex three- dimensional geometries and easy up- scaling. In order to investigate the potential of hot filament CVD for different applications a multifilament HFCVD reactor with a deposition area of 20X20 cm² has been developed. Optimisation of deposition conditions like gas flow control, gas phase composition, filament temperatures and adjustments of substrate and filament arrangement geometries yielded homogeneous depo sition over the whole area and diamond growth rates up to 3 µm/h for a twelve filament array. By controlling the gas phase composition, especially the relation of carbon to atomic hydrogen, and substrate temperature in HFCVD it is possible to deposit (001) textured diamond films. Cemented carbide tools have also been coated with (001) textured diamond, resulting in smooth cutting edges demonstrating the uniformity of three dimensional coating. An evaluation of the multi-filament process for economic production of CVD diamond products like heat spreaders, cutting tools, wear resistent parts and diamond electrodes for electrochemical applications will be given. As a perspective first results of up-scaling the deposition area to 80X40 cm² will be reported.