Formation of patterned buried insulating layer in Si substrates by He+ implantation and annealing in oxidation atmosphere

We fabricated patterned buried insulating layers in a Si substrate by implanting He+ ions through a patterned mask and annealing in an oxidation atmosphere. Compared with patterned O+ implantation and annealing, this technique causes less damage, and can therefore reduce defect density at the edge of the patterned buried insulator. The buried insulator could be SiO2 or a void with thin SiO2 film on the inner surface. The formation of a void could further reduce defect density, probably because the stress induced by SiO2 formation is small. The fabricated surface was extremely smooth within the focal depth limitations of state-of-the-art photolithography techniques.