Selective Growth of Polycrystalline Diamond Thin Films
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SELECTIVE GROWTH OF POLYCRYSTALLINE DIAMOND THIN FILMS R. RAMESHAM Electrical Engineering Department, Alabama Microelectronics Science and Technology Center, Auburn University, Auburn, AL 36849-5201 ABSTRACT Microwave plasma assisted CVD is employed to grow diamond films using a gas mixture of H 2 and CH, on various substrates. Diamond has a tendency not to nucleate growth on mirror-smooth finished substrates irrespective of the substrate type (except single crystal diamond). We have developed various processes to enhance the nucleation density of the diamond substantially by damaging or seeding the surface of the substrates. Several process techniques such as 1. silicon nitride and silicon dioxide process, 2. ultrasonic agitation process, 3. selective seeding of diamond by electroplating of Cu, 4. patterning of diamond films by air-microwave plasma etching, etc., were developed to achieve the patterns of diamond on various substrates. Selective growth of doped diamond and low temperature growth of diamond for microelectronic applications have also been achieved by using the above processes (1 and 2). Details on selective diamond growth processes and the morphology of as-deposited selective diamond by SEM are presented. INTRODUCTION Growth of diamond th~in films using microwave assisted CVD has attained considerable interest in recent years, since this material has unique physical and chemical properties [13]. Many of the potential microelectronic applications require patterned thin films of diamond. Patterning can usually be achieved by chemical etching, plasma etching or dry etching, selective deposition, selective seeding, etc. Diamond is highly chemically inert and therefore, patterning of diamond by chemical etching is questionable. Selective deposition of diamond can be achieved if the two regions on a desired substrate have a nucleation density differing by several orders of magnitude. It is well known that the nucleation density is very low on mirror-smooth finished substrates and increased by several orders of magnitude upon damaging the surface [4,5]. Several selective diamond deposition techniques have been reported [6-12] by different research groups. In our laboratory, selective growth of diamond has been achieved by patterning the scratch damaged or by selectively damaging the mirror-smooth finished surface of the substrate. Diamond is typically grown at a substrate temperature of 600-9500 and therefore, photoresist cannot be used as a mask material to grow diamond selectively. In this paper, I report on the selective growth of diamond films by various approaches, patterning of diamond films by plasma etching, and selective diamond growth via selective seeding of the substrates. EXPERIMENTAL DETAILS A commercially available (ASTeX, Cambridge, MA) microwave plasma system was used in our experiments to deposit diamond films and the process details of diamond deposition
Mat. Res. Soc. Symp. Proc. Vol. 282. 01993 Materials Research Society
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are described earlier [13-17). Typical parameters to depos
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