Time-multiplexed etching, the Bosch process, is a technique consisting of alternating etch and deposition cycles to produce high aspect-ratio etched features. The Bosch process uses SF 6 and C 4 F 8 as etch and polymer deposition gases, respectively. In these experiments, polymer thickness is controlled by both C 4 F 8 gas flow rates and by deposition cycle time. The authors show that polymer thickness can be used to control wall angle and curvature at the base of feature walls. Wall angle is found to be independent of trench width under thin-polymer deposition conditions. Experimental results are compared to results obtained by other researchers using the more conventional simultaneous etch/deposition technique.

Turbulent premixed oxygen-acetylene flames have been used to synthesize polycrystalline diamond films on molybdenum substrates at temperatures ranging from 500 to 1300 °C and facetted single crystals on mm-sized natural diamond substrates at temperatures of 1200–1300 °C. Turbulence was achieved by increasing the torch’s orifice diameter and/or the flow velocity; the presence of turbulence was confirmed by observations of changes in the flame shape, measurements of the flame’s noise spectrum, and calculations of the Reynolds number. The optical emission spectra of several diamond-growing turbulent flames were also compared to the spectra of laminar flames. The variation in diamond quality with temperature and oxygen acetylene flow ratio was studied with one or more of the following techniques: Raman spectroscopy, scanning and transmission electron microscopy, infrared spectroscopy, and photoluminescence spectroscopy. Crystals grown on molybdenum at temperatures of 600–1100 °C were observed to be transparent, and under the proper conditions the quality of diamond grown epitaxially in a turbulent flame equals that of natural type-IIa diamond. Although this enhanced quality has only been observed for fairly lean flames, the growth rate for type-IIa quality diamonds can still exceed 35 μm/h.

High quality polycrystalline diamond films have been synthesized in a premixed, turbulent oxygen-acetylene flame, using a commercial brazing torch. The quality of the films was measured by Raman spectroscopy, electron microscopy, and hemispherical transmittance measurements in the ultraviolet, visible, and infrared. Turbulence was achieved by operating the torch with a sufficiently high Reynolds number. The presence of turbulence was confirmed by observations of changes in the flame shape, the characteristic sound of the flame, and calculation of the Reynold’s number.