LIMITING PROCESSES FOR DIAMOND EPITAXIAL ALIGNMENT ON SILICON

For the heteroepitaxial deposition of diamond on silicon using the bia s-enhanced nucleation procedure, several different processes contribut ing to the final misalignment of the layers can be identified: (i) The interface of Si/diamond or Si/SiC and SiC/diamond, respectively. (ii) The growth of individual grains during the biasing process. (iii) The growth competition between differently oriented grains and their coal escence during the growth of thick films. X-ray-diffraction texture st udies revealed that the azimuthal alignment is essentially determined by the nucleation step. Oriented nucleation is only possible within a defined time window. Within this time window the azimuthal misalignmen t shows a characteristic variation depending on the absolute value of the bias voltage. The alignment of the SiC interlayer as measured by s ynchrotron radiation cannot explain the observed variation. In contras t, texture measurements of thick oriented films after exposure to the bias conditions suggest that the limitation of the process time window for oriented nucleation as well as the variation of misorientation wi th biasing time can be traced back to the detrimental effect of bias-a ssisted growth. Based on this mechanism, a model is proposed which all ows one (a) to describe the temporal development of the azimuthal miso rientation within the process time window, and (b) to estimate the con tribution of bias-assisted growth on the misorientation. Finally, some epitaxial diamond films have been deposited on high-quality beta-SiC layers. A minimum value of 2.9 degrees for the width of the azimuthal distribution has been found.