Process for producing structural body and etchant for silicon oxide film

A process for producing a structural body comprising a substrate and a structural layer formed on the substrate through an air gap which structural layer functions as a micro movable element, said process comprising:

• a film-deposition step of successively forming a sacrificial layer made of a silicon oxide film and the structural layer on the substrate to form a laminate;
• and
• a subsequent air gap-forming step comprising the steps of:
• (a) feeding a first treating fluid prepared by adding hydrogen fluoride, a water-soluble organic solvent and water to a supercritical carbon dioxide fluid into a single-bath chamber of a treating apparatus containing the laminate, thereby etching the sacrificial layer of the laminate and cleaning the laminate;
• (b) feeding the supercritical carbon dioxide fluid containing only the water-soluble organic solvent into the chamber as a second treating fluid, thereby rinsing the laminate while replacing the first treating fluid with the second treating fluid;
• (c) feeding only the supercritical carbon dioxide fluid to the chamber as a third treating fluid, thereby rinsing the laminate while replacing the second treating fluid with the third treating fluid;
• and
• (d) drying the laminate by gasifying and removing the supercritical carbon dioxide fluid fed as the third treating fluid,
• said steps (a) to (d) being sequentially conducted in the chamber in this order.