Selective deposition of diamond onto Si substrates using tetraethylorthosilicate SiO 2 films as masks

Abstract

Tetraethylorthosilicate (TEOS) SiO 2 films were deposited by r.f. plasma enhanced chemical vapor deposition (CVD) at low temperature (573 K). Using a hot-filament CVD method, polycrystalline diamond films were deposited selectively onto roughened (scratched with diamond paste or cleaned ultrasonically with diamond powder suspension) Si substrates using patterned TEOS SiO 2 films as masks. The experiments show that the diamond nucleation density on the TEOS SiO 2 masked area of the Si substrate is strongly affected by the temperature of the substrate. At low temperature (973–1103 K), selective deposition of diamond film onto Si was achieved using TEOS SiO 2 masks. With increasing substrate temperature, the diamond nucleation density of the TEOS SiO 2 masked area increased (1103–1133 K), and even exceeded that on the unmasked area (above 1133 K). The stability of the TEOS SiO 2 masks and diamond nucleation on the TEOS SiO 2 masks in the deposition process were studied. The diamond nucleation density on the TEOS SiO 2 masked area was found to be affected by the concentration of methane in hydrogen: an increase in the concentration of methane (ratio of methane to hydrogen larger than 0.6%) appears to inhibit the emergence of defects on teh TEOS SiO 2 mask to decrease the nucleation density, and increase the non-diamond component of the diamond film. It is suggested that the defects and/or cracks on the TEOS SiO 2 mask caused by hydrogen etching and/or thermal stresses produced during CVD processing are the main reasons for the increase in diamond nucleation on the SiO 2 masked area.