Investigation of bias enhanced nucleation of diamond on silicon

Abstract

The process of bias enhanced nucleation of microwave chemical vapor deposited diamond on silicon has been extensively characterized using plasma diagnostics, scanning and transmission electron microscopy (TEM), Raman spectroscopy, and x-ray diffraction. The nucleation kinetics were measured as a function of bias voltage, methane partial pressure, and substrate temperature. The nucleation is found to be transient in character, with a delay time followed by an exponential increase in nucleation density with time, and finally a saturation. The ion flux and ion energy distribution was measured by a retarding field probe. The nucleation density was found to reach a maximum at a bias at which the ion energy distribution has a maximum of 80 eV, independent of the substrate temperature. This is taken as strong evidence that nucleation enhancement involves ion subplantation. The Raman spectra and x-ray diffraction suggests that the films during nucleation consist primarily of sp2 bonded noncrystalline carbon. The presence of the (0002) interlayer graphitic peak suggests that the carbon is primarily graphitic. The diamond nuclei form in this matrix. TEM shows mainly amorphous hillocks being formed on the substrates by bias enhanced nucleation. Diffraction patterns and high resolution TEM reveal the presence of β-SiC and also a small number of diamond particles.

Crystal morphology and phase purity of diamond crystallites during bias enhanced nucleation and initial growth stages

“…BEN nucleation requires an incubation time as previously reported by Stoner et al 3 and Gerber et al 18 The nucleation incubation time, in our experiments, was found to vary across each sample. In the central region, assigned A, some small islands were formed after 5 min bias enhanced nucleation, as shown in Fig.…”

“…The corresponding bias voltage and duration are also listed. Oriented region ͑mm from the center͒ 10-35 14-32 15-30[15][16][17][18][19][20][21][22][23][24][25] …”

Synthesis and characterization of smooth ultrananocrystalline diamond films via low pressure bias-enhanced nucleation and growth

“…2,6 The film adhesion, surface roughness, and growth rate of UNCD films are controlled by nucleation and growth processes. [6][7][8] The biasenhanced nucleation ͑BEN͒ process investigated by several groups has several advantages over mechanical polishing or ultrasonic seeding processes, namely, ͑a͒ better efficiency, 9 ͑b͒ stronger adhesion to substrates, [8][9][10][11] and ͑c͒ an integrated fully dry nucleation/growth process using plasma processing only. Prior work 8 demonstrated that the BEN process enhances UNCD film adhesion to substrates, although UNCD films were grown using an Ar/ CH 4 chemistry without bias, on BEN layers produced by 70 mbar H 2 / CH 4 plasma chemistry.…”

A Nucleation Site and Mechanism Leading to Epitaxial Growth of Diamond Films

“…Experimental methods for diamond nucleation on nondiamond substrates (the first necessary step of a heteroepitaxial growth process) have also been developed (4-7). The most effective method uses bias-enhanced nucleation (BEN) (4,(6)(7)(8)(9)(10), in which the target is biased, with a relatively methanerich CH 4 /H 2 mixture (several percent methane) as a first step, followed by a conventional CVD step (typically 1% methane or less). However, the nucleation mechanism of diamond on nondiamond substrates remains poorly understood (11), largely because of the tremendous difficulty of locating and identifying the nucleation sites.…”