| 摘要 |
The method comprises two steps of isotropic etching. The first-step etching has a loading effect and is carried out on a substrate through a mask comprising a set of openings substantially point-like or circular laid out in an array, and the area of each opening is determined by the required depth of etching below the opening. The second-step etching of the substrate is carried out without the mask. The mask is deposited onto the substrate, and removed after the first-step isotropic etching. The etching is isotropic, that is extended at substantially the same speed laterally as well as orthogonally to the surface of the substrate. The first and/or the second etchings are reactive ionic etchings (RIEs) carried out in isotropic conditions, e.g. associated with the etching of type SF6 at high pressure and low power, or chemical etchings carried out in isotropic conditions. The depth of etching is increased from the centre to the edge of the mask, that is from a smaller opening to a larger opening. The second etching allows polishing of the substrate surface, that is reduces the surface roughness, e.g. to below 30 nm in about 20-50 minutes. The substrate is a semiconductor wafer, and the mask (11) is of aluminium. The method is utilized for manufacturing microscopic lenses. |
