{HEAD ~ The porous insulation layer} may be formed by first forming a composite layer of an extractable material and a matrix forming insulation material over the integrated circuit structure on a semiconductor wafer, and then selectively removing {TAIL ~ the extractable material} from the matrix forming material, without damaging the remaining matrix material, thereby leaving behind a porous matrix of the insulation material 
formed by selectively removing
{ HEAD ~ The porous insulation layer } may be formed by first forming a composite layer of an extractable material and a matrix forming insulation material over the integrated circuit structure on a semiconductor wafer , and then selectively removing { TAIL ~ the extractable material } from the matrix forming material , without damaging the remaining matrix material , thereby leaving behind a porous matrix of the insulation material
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