Microfabrication of diamond films by localized electron beam chemical vapour deposition

We have investigated the microfabrication of diamond films on silicon substrates using the localized electron beam (EB) chemical vapour deposition (CVD) method with a hydrogen (H-2) and methane (CH4) mixed gas source. Micro-Raman spectra at 1, 3 and 5% CH4 concentrations for the accelerating voltage of 10 kV have indicated the presence of a diamond (sp(3) bonding) peak at 1333 cm(-1), a graphite (sp(2) bonding) peak at 1580 cm(-1) and a diamond peak, and an amorphous carbon peak at 1360 cm(-1) and graphite peak, respectively; those at 7 and 10% concentrations have indicated broad amorphous carbon peaks around 1500 and 1300 cm(-1). We have found that the films consist of a mixture of sp(3) and sp(2) bonded structures. The film quality (sp(3)) content decreases with increasing CH4 concentration. Consequently, the localized EB CVD diamond films have been fabricated under the following deposition conditions: an accelerating voltage of 10 kV and a CH4 concentration of 1%. The EB was scanned in areas of 2 x 10 mum(2) rectangle and 1 x 1 mum(2) square on a silicon substrate. The two-dimensional cross-sectional profiles (X-Z axis) of the resulting micro-rectangular diamond patterns were very similar to those of the resulting micro-square diamond patterns. The deposited thickness of the resulting micro-rectangular and square diamond patterns increased linearly with increasing EB irradiation time up to a limit of 10 h. The deposition rate was approximately 0.1 mum h(-1) in both cases. The full width at half maximum (FWHM) of the cross-sectional profiles, having the triangular form of the resulting micro-rectangular and square diamond patterns, first increased with increasing EB irradiation time and reached a maximum width at an EB irradiation time of 4 and 6 h, respectively and then decreased gradually with a further increase of the EB irradiation time. The deposited thickness and FWHM of the resulting micro-rectangular and square diamond patterns for a 10 h EB irradiation time were 1.1, 0.98 mum and 3.6, 3.3 mum, respectively.