Tantalum plasma etching with minimum effect on underlying nickel-iron thin film

Removing tantalum (Ta) from nickel-iron (NiFe) surface in CF4/O-2 plasma was first demonstrated to be a more robust process than argon ion milling in preserving and controlling the NiFe magnetic thickness during Ta overetch. A factorial study showed that the NiFe magnetic thickness loss could be further reduced by replacing CF4 with CHF3 and reducing O-2 flow. For an optimized CHF3/CF4 process, the NiFe magnetic thickness loss for a 100-Angstrom Ta overetch was only 5 Angstrom. Electron spectroscopy for chemical analysis showed the presence of the fluorocarbon on the CF4/CHF3 etched Ta surface and nickel fluoride on the NiFe surface after Ta overetch. A mechanism of removing tantalum with minimum effect on the underlying nickel-iron thin film was also proposed. (C) 1997 Elsevier Science S.A.