Selected-area diamond deposition on Si substrates pre-treated in different ways

Abstract

Using a hot-filament chemical vapour deposition (CVD) method, polycrystalline diamond films have been selectively deposited on Si(111) substrates pre-treated in different ways: roughened Si substrates with patterned Si 3N 4 mask, and polished Si substrates with selected-area ultrasound treatment by diamond powder. It has been demonstrated that the nucleation density of diamond deposited on the Si 3N 4 masked area of roughened Si substrate is strongly affected by the temperature on the surface of the substrate while that on the untreated area of polished Si substrate is less affected by the substrate temperature. The diamond nucleation density on the Si 3N 4 masked area has been shown to be more markedly affected by the concentration of CH 4 in H 2 than that on the untreated Si area. It is suggested that the defects and cracks on the Si 3N 4 mask caused by hydrogen etching and thermal stresses produced during CVD processing are the main reasons for the increase in diamond nucleation on the Si 3N 4 masked area. The increase in the concentration of CH 4 in H 2 appears to inhibit the emergence of defects on the Si 3N 4 mask. It is also suggested that the internal stresses in the Si substrate, chemical etching from hydrogen atoms and other factors cause defects and cracks on polished Si at substrate temperatures of above 900°C, which lead to an increase in diamond nucleation on the untreated area of the polished Si substrate.