FIB process for selective and clean etching of copper

A method of focused ion beam etching of copper in the presence of a dielectric in a focused ion beam vacuum chamber, comprising:

• directing a focused ion beam onto a portion of the copper to be etched;
• and
• exposing the copper to an etch assisting gas comprising a first compound selected to protect the dielectric from etching, the first compound being selected from the group consisting of Hydrazine Monohydrate and a hydrazine derivative, the first compound having a boiling point of about 220° C. or lower, and a second compound comprising Nitrogen Tetroxide to render sputtered conductive copper non-conductive.

A method of focused ion beam etching of copper in the presence of a dielectric in a focused ion beam vacuum chamber, comprising:

• directing a focused ion beam onto a portion of the copper;
• exposing the copper and the dielectric to an etch assisting gas comprising a compound selected from the group of NitrosAmines and NitrosAmine related compounds consisting of NDMA, NMEA, NDEA, NMPA, NEPA, NDPA, NMBA, NEBA NPYR, NPIP, NMOR and Carmustine, said compounds having the chemical structure R1N(—R2)—N═O, where R1 and R2 are linear or branched hydrocarbon or halogenated hydrocarbon groups.