Selective deposition of diamond onto Si substrates using tetraethylorthosilicate SiO₂ films as masks

Tetraethylorthosilicate (TEOS) SiO₂ 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 SiO₂ films as masks. The experiments show that the diamond nucleation density on the TEOS SiO₂ 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 SiO₂ masks. With increasing substrate temperature, the diamond nucleation density on the TEOS SiO₂ masked area increased (1103-1133 K), and even exceeded that on the unmasked area (above 1133 K). The stability of the TEOS SiO₂ masks and diamond nucleation on the TEOS SiO₂ masks in the deposition process were studied. The diamond nucleation density on the TEOS SiO₂ 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 the TEOS SiO₂ 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 SiO₂ 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 SiO₂ masked area.