A fabrication method for an air-gap, in which method hard mask is used, is described. A patterned hard mask layer is formed on a semiconductor substrate. Taking advantage of the etching selectivity of the hard mask layer to the dielectric layer, an opening with a high aspect ratio is formed in the dielectric...http://www.google.com.au/patents/US6277705?utm_source=gb-gplus-sharePatent US6277705 - Method for fabricating an air-gap with a hard mask
