Novel in situ production of smooth diamond films
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Novel in situ production of smooth diamond films Donald R. Gilbert, Dong-Gu Lee, and Rajiv K. Singh Materials Science and Engineering, University of Florida, Gainesville, Florida 32611 (Received 3 September 1997; accepted 9 February 1998)
We have developed a unique method to produce smooth diamond films using a modified microwave plasma process system. This method consists of sequential in situ deposition and planarization in an electron cyclotron resonance plasma system. Diamond films were deposited to a thickness of 3.0 mm in this system at a pressure of 1.000 Torr from gas mixtures of methanol and hydrogen. Deposition was followed by planarization using a two-grid ion beam extraction process with a pure oxygen plasma at 10 mTorr. The average roughness of the diamond films so produced was as low as 30 nm, which was a factor of two lower than that of the as-deposited diamond films.
Typical polycrystalline diamond films produced by chemical vapor deposition (CVD) exhibit high surface roughnesses as a result of their columnar growth structure that is not desirable for many applications, such as optical coatings and microelectronic or micromechanical structures. As a result, methods are being widely sought to produce low surface roughness diamond films. The most common method for producing low roughness surfaces is by polishing after the film is deposited. The extreme hardness and relatively inert nature of diamond make it difficult to polish by standard methods. Several methods, including chemical mechanical polishing, inert and oxygen ion beam polishing have been developed to smoothen diamond films after CVD deposition.1–5 In situ production of diamond films has several advantages with respect to post-processing techniques. Besides reduction in processing costs, processing time can be reduced while maintaining a cleaner process environment. In recent years, controlled, high nucleation density techniques, such as bias enhanced nucleation (BEN) or nanoparticle seeding, have been employed to reduce the as-deposited roughness of diamond films.6,7 In this paper we have investigated a novel electron cyclotron resonance (ECR) plasma based in situ deposition and polishing method to synthesize diamond films. An ECR plasma system is particularly well adapted to the dual processes of deposition and polishing of diamond films. This is the result of its enhanced plasma generation capabilities at pressures below 10.0 Torr.8,9 Deposition of diamond requires energetic activation and dissociation of deposition precursors and the formation of specific monomer species such as the methyl radical (CH3 ). Low pressure operation (&1.0 Torr) provides longer diffusion lengths with correspondingly longer transient species lifetimes that facilitate uniform depoJ. Mater. Res., Vol. 13, No. 7, Jul 1998
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sition over larger areas and multiple substrates, and also low temperature deposition.10–13 The polishing of the diamond can be accomplished
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