Growth and Characterization of Polycrystalline Diamond Thin Films on Porous Silicon by Hot Filament Chemical Vapor Depos
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ABSTRACT Hot filament chemical vapor deposition (HFCVD) was utilized to grow high quality diamond film on porous silicon (PS) substrates to a thickness of 5-6 gtm. Boron-doped silicon substrates of orientation and resistivity of 5-15 ohm-cm were anodized by the electrochemical process to form PS. A slurry of diamond paste (1/4 micron average grain size) was rubbed on the samples for a few seconds before introduction into the chamber. Diamond film growth on the PS has the advantages of shorter incubation time and higher nucleation density as evident from scanning electron microscopy (SEM). The results of X-ray diffraction confirm the growth of predominatly (111) oriented high quality diamond film. Electrical properties were also studied by sputtering circular gold contacts on top of diamond film and measuring current-voltage (I-V) characteristics. INTRODUCTION The nucleation and growth of polycrystalline diamond thin films on silicon (as the dominant material in semiconductor industry) has been the subject of intense investigation. The effects of Si surface pretreatment on the nucleation enhancement of diamond has been studied by many researchers. 1 -2 One of the most useful techniques in promoting nucleation and growth
of diamond films with reduced stress is the formation of PS layers on silicon substrates. Porous silicon is quickly becoming an increasingly important and versatile electronic material in today's fabrication technology. Ever since Canham 3-5 demonstrated visible light photoluminescence from PS, much effort has been focused on the possibility of producing optoelectronic devices using this material.6 9 Diamond growth on PS by chemical vapor deposition was reported for the first time by Spitzl et. al.10 These authors demonstrated that PS allows for a reduction of the stress in diamond film as well as enhancing the quality of the diamond structure. Another group of authors" have shown that PS (compared to mechanically scratched Si) has a smoother surface and more evenly distributed defects for the growth of diamond film. They also investigated the infrared transmission spectra and concluded that the transmittance of diamond film grown on PS is higher than for film grown on silicon substrates. Diamond nucleation and growth on PS substrates is the focus of the present work. The study of anodization conditions and their effect on the nucleation density and the quality of grown diamond films was carried out to determine the most suitable set of parameters for formation of porous layers. Electrical characteristics of the deposited diamond film were studied by observing the I-V data on a gold-diamond-PS-Si structure.
415 Mat. Res. Soc. Symp. Proc. Vol. 423 c 1996 Materials Research Society
EXPERIMENT In this work, several boron-doped Si samples of orientation and resistivity of 515 ohm-cm were used as starting substrates. These samples underwent organic cleaning in an ultrasonic bath with trichloroethylene, acetone, methanol, and DI water for five minutes each. Substrates were further cleaned in hot nitric
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