Etch assisting agents for
focused ion beam (FIB)
etching of
copper for circuit editing of integrated circuits both prevent loss of adjacent
dielectric due to
sputtering by the
ion beam, and render sputtered re-deposited
copper on adjacent surfaces non-conductive to avoid electrical short circuits. The agents are characterized by having an N—N (N being
Nitrogen) bonding in their molecules and boiling points between about 70° C. and about 220° C., and include hydrazine and water solutions,
hydrazine derivatives,
NitrosAmine derivatives saturated with two
hydrocarbon groups selected from Methyl, Ethyl, Propyl and Butyl,
NitrosAmine related compounds, and
Nitrogen Tetroxide. Preferred agents are
Hydrazine monohydrate (HMH), HydroxyEthylHydrazine (HEH), CEH, BocMH, BocMEH, NDMA, NDEA, NMEA, NMPA, NEPA, NDPA, NMBA, NEBA, NPYR, NPIP, NMOR and
Carmustine, alone or in combination with
Nitrogen Tetroxide. The agents are effective for
etching copper in high
aspect ratio (deep) holes.