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The deposition of uniform, low-stress, thick and thin films of ultrananocrystalline diamond (UNCD) is investigated. The process methods and apparatus that enable the uniform and smooth deposition of both thin and thick (> 50 μm) UNCD across 3 in. diameters are described. UNCD films are synthesized by microwave plasma-assisted CVD using Ar/H 2 /CH 4 input gas mixtures over a wide pressure range (60–240 Torr) and temperature range (400–850 °C). Films were grown on 3 in. diameter silicon substrates with thicknesses ranging from 58 nm to greater than 50 μm. Film surface roughness as low as 10 nm (AFM) was obtained. Film uniformities of 70 to over 95% were achieved on 3 in. diameter silicon substrates. The growth rate increased as pressure, percent hydrogen and percent methane in the gas mixture, and microwave power increased. The highest growth rate 1.12 μm/h was achieved at 180 Torr, H 2 /Ar/CH 4 = (4:100:2) sccm and 1.5 kW absorbed power. Overall, a robust, repeatable process has been demonstrated for the deposition of UNCD films.

The influence of varying nitrogen concentrations (5–1000 ppm) on the conventional CH 4 /H 2 diamond film deposition process using a microwave plasma disk reactor is investigated. This reactor has important differences, such as reactor volume, power density, gas flow, from the common tubular microwave reactors. The experimental behavior indicates, that similar to the tubular reactors, the addition of small amounts of a nitrogen stabilizes the growth of high quality, {100} faceted films. However, the actual threshold nitrogen concentrations and the variation of these threshold concentrations versus other independent experimental variables differs considerably from tubular reactor performance. This suggests that reactor design has an important influence on the deposition process in the presence of impurities.

Summary form only given. It has been shown that even small concentrations of nitrogen have a substantial effect on the growth of CVD diamond films, while larger concentrations may result in degraded and rough growth. In the present study we show the effect of nitrogen concentration on the growth, texture, morphology, and crystalline quality of CVD diamond films. All films are heteroepitaxially grown on a 3 inch silicon substrate and are scratch-seeded with a seeding density of 10/sup 9//cm/sup 2/. A computer controlled 5 inch discharge 2.45GHz microwave plasma reactor with ultra-high vacuum gas handling systems combined with optical emission spectroscopy allows exact control of the gas phase concentrations and reactor input variables. Nitrogen gas phase concentration is varied from l0ppm to over 1000ppm and is controlled by the measurement of CN bands in the optical emission spectrum of the plasma. Pressure ranges from 38-50 Torr, methane/hydrogen from 0.5-2%, and flow rate from 50-200 sccm. Growth and morphology are carefully determined using SEM while texture is obtained using XRD. Crystalline quality is measured by determining the FWHM of the diamond Raman peak at 1332/cm using unpolarized micro-Raman spectroscopy. Detailed growth, texture, morphology, and crystalline quality maps are given to show the sequential effect of increasing nitrogen versus all other reactor input variables.

Summary form only given. Recent studies within our group have focused on the effects of nitrogen on diamond film growth. Very small concentrations of nitrogen have been shown to enhance CVD diamond film growth, while larger concentrations may result in rough growth. In any CVD growth, within several gas phase mean free paths of the surface, the composition of the gas is perturbed by the effects of the reactions occurring at the surface. A chemical boundary layer with temperature and concentration gradients is formed, through which species diffuse to reach the surface. Boundary layer transport in CVD diamond film growth has been studied for hydrogen, carbon and oxygen species. The transport of nitrogen has been less studied. Also the transport mechanisms and growth are somewhat specific to deposition conditions. Our deposition conditions are based on use of a five inch discharge 2.45 GHz microwave plasma reactor, and transport over wide areas has also been less studied.

Summary form only given, as follows. Argon-methane and argon-methane-hydrogen discharges used in a microwave CVD system for the deposition of diamond films are investigated in this study. These discharges have been used to produce small grain size diamond films, also known has ultra-nanocrystalline diamond. To further understand the plasma deposition process experimental measurements of the discharges have been undertaken. Specifically, the objective of this study is to determine the relationship of the deposition results versus plasma species concentrations and temperatures. The deposition discharges being studied are at pressures of 80-160 Torr with 0-3% methane and 0-10% hydrogen in an argon discharge. The plasma discharges studied are excited using a 17.8 cm diameter microwave resonant cavity reactor. The discharges are excited using 2.45 GHz microwave power in a discharge chamber with 12.5 cm diameter. Experimental characterizations include OES measurements of selected atomic hydrogen, C/sub 2/, and CH emission lines, and OES measurements of gas temperature in the discharge. Changes in the input gas composition are observed to produce substantial variations in these OES measurements. The measurements are conducted as functions of the discharge's quartz wall temperature (100-200 C) and the substrate temperature (400-900 C). The discharge experimental measurement results are also correlated with the properties of the diamond films deposited.