Patent ID: 7767587

Claim:
A method of forming a pre-metallized interconnect structure comprising: providing a structure comprising an etch stop layer comprising a porous organosilicated glass located between a first non-porous organosilicate glass interlevel dielectric and a second non-porous organosilicate glass interlevel dielectric, said porous organosilicate glass having a carbon content that is greater than the carbon content in the first and second non-porous organosilicate glass interlevel dielectrics; and patterning said structure to provide an opening that extends through the structure, said patterning comprising lithography and etching, wherein said etching is performed in a fluorocarbon-based plasma having a fluorine to carbon ratio and at an ion current that selectively etches the non-porous organosilicate glass interlevel dielectrics relative to the porous organosilicate glass, whereby a material of said second non-porous organosilicate glass interlevel dielectric is removed selective to said porous organosilicate glass during said etching through formation by said fluorine-based plasma of a SiC-like film that impedes further etching at a surface of said etch stop layer.